stop the layout dialog opening for a shipyard with no schematic

Clearing a shipyard with "(None)" opened the layout configuration dialog on a
grid of no cells. The auto-open guard asked only whether the chosen id differs
from the current one, and the "(None)" option carries the empty id, which
differs from every schematic; ShipLayoutDialog then found no ship def and
derived a 0x0 grid. Predates this branch -- 698dd4d, 2026-07-13.

The question all three sites were answering by hand is now one:
findLayoutShipDef() returns the ship to configure a layout against, or nullptr
when no schematic is set, the id names no ship, or the ship defines no grid.
The auto-open path and the LayoutDialogRequestedEvent handler now ask it
before opening, and ShipyardContent asks it instead of spelling the same test
out for the preview and the Configure button.

The event handler was reachable only through a button ShipyardContent already
disables, so guarding it changes nothing today; it is guarded because the
dialog's precondition belongs to the dialog's entry, not to the widget that
happens to be the only caller.

REQ-MOD-UI-AUTO-DIALOG said "differs" and left clearing implicit, which is the
reading the code took. It now says clearing opens nothing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ne3mejABZoLWKLh8fgpM3x

bin/app/data/config/recipes.toml

@@ -6,6 +6,10 @@
 # realized: tier 1 ratios are 1:1, tier 2 ratios are 2:3, tier 3+ ratios
 # are deliberately strange.
 #
+# A recipe id names the process, not the product — the display name shown in
+# the UI is derived from it — so an item and the recipe that makes it never
+# carry the same name.
+#
 # Input chain per game phase — each phase transition adds exactly one new
 # base input:
 #
@@ -27,21 +31,21 @@
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "mine_iron_ore"
+id = "iron_mining"
 building = "miner"
 inputs = []
 outputs = [{item = "iron_ore", amount = 1}]
 duration_seconds = 1.0
 
 [[recipe]]
-id = "mine_copper_ore"
+id = "copper_mining"
 building = "miner"
 inputs = []
 outputs = [{item = "copper_ore", amount = 1}]
 duration_seconds = 1.0
 
 [[recipe]]
-id = "mine_quartz"
+id = "quartz_mining"
 building = "miner"
 inputs = []
 outputs = [{item = "quartz", amount = 1}]
@@ -52,21 +56,21 @@ duration_seconds = 2.0
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "iron_ingot"
+id = "iron_smelting"
 building = "smelter"
 inputs = [{item = "iron_ore", amount = 1}]
 outputs = [{item = "iron_ingot", amount = 1}]
 duration_seconds = 1.0
 
 [[recipe]]
-id = "copper_ingot"
+id = "copper_smelting"
 building = "smelter"
 inputs = [{item = "copper_ore", amount = 1}]
 outputs = [{item = "copper_ingot", amount = 1}]
 duration_seconds = 1.0
 
 [[recipe]]
-id = "silicon"
+id = "quartz_reduction"
 building = "smelter"
 inputs = [{item = "quartz", amount = 1}]
 outputs = [{item = "silicon", amount = 1}]
@@ -90,51 +94,47 @@ duration_seconds = 1.0
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "reprocessing_cycle"
+id = "scrap_reprocessing"
 building = "reprocessing_plant"
 inputs = [{item = "scrap", amount = 4}]
 duration_seconds = 4.0
 
-  [[recipe.outputs]]
-  item = "iron_ingot"
-  amount = 1
+  [[recipe.output_group]]
   probability = 0.3
+  items = [{item = "iron_ingot", amount = 1}]
 
-  [[recipe.outputs]]
-  item = "copper_ingot"
-  amount = 1
+  [[recipe.output_group]]
   probability = 0.3
+  items = [{item = "copper_ingot", amount = 1}]
 
-  [[recipe.outputs]]
-  item = "silicon"
-  amount = 1
+  [[recipe.output_group]]
   probability = 0.2
+  items = [{item = "silicon", amount = 1}]
 
-  [[recipe.outputs]]
-  item = "voidsteel"
-  amount = 1
+  [[recipe.output_group]]
   probability = 0.2
+  items = [{item = "voidsteel", amount = 1}]
 
 # -----------------------------------------------------------------------------
 # Tier 2 — early intermediates (clean ratios, ~2:3)
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "steel_plate"
+id = "steel_rolling"
 building = "assembler"
 inputs = [{item = "iron_ingot", amount = 2}]
 outputs = [{item = "steel_plate", amount = 1}]
 duration_seconds = 3.0
 
 [[recipe]]
-id = "copper_wire"
+id = "wire_drawing"
 building = "assembler"
 inputs = [{item = "copper_ingot", amount = 1}]
 outputs = [{item = "copper_wire", amount = 2}]
 duration_seconds = 1.0
 
 [[recipe]]
-id = "copper_coil"
+id = "coil_winding"
 building = "assembler"
 inputs = [{item = "copper_wire", amount = 2}]
 outputs = [{item = "copper_coil", amount = 1}]
@@ -145,7 +145,7 @@ duration_seconds = 1.5
 # unlocked_at_start: building blocks appear in no schematic's materials, so the
 # implicit item graph can never reach this recipe (REQ-LOCK-IMPLICIT).
 [[recipe]]
-id = "building_block"
+id = "block_pressing"
 building = "assembler"
 unlocked_at_start = true
 inputs = [{item = "steel_plate", amount = 2}]
@@ -157,14 +157,14 @@ duration_seconds = 2.0
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "control_chip"
+id = "chip_etching"
 building = "assembler"
 inputs = [{item = "silicon", amount = 1}, {item = "copper_wire", amount = 2}]
 outputs = [{item = "control_chip", amount = 1}]
 duration_seconds = 5.0
 
 [[recipe]]
-id = "capacitor_bank"
+id = "capacitor_assembly"
 building = "assembler"
 inputs = [{item = "copper_coil", amount = 2}, {item = "silicon", amount = 1}]
 outputs = [{item = "capacitor_bank", amount = 1}]
@@ -173,21 +173,21 @@ duration_seconds = 5.0
 # The quality gate for m+ hulls: a deliberately long-running recipe
 # (time-heavy archetype).
 [[recipe]]
-id = "hardened_steel"
+id = "steel_hardening"
 building = "assembler"
 inputs = [{item = "steel_plate", amount = 3}]
 outputs = [{item = "hardened_steel", amount = 1}]
 duration_seconds = 12.0
 
 [[recipe]]
-id = "ceramic_plate"
+id = "ceramic_firing"
 building = "assembler"
 inputs = [{item = "quartz", amount = 2}]
 outputs = [{item = "ceramic_plate", amount = 1}]
 duration_seconds = 4.0
 
 [[recipe]]
-id = "drive_unit"
+id = "drive_assembly"
 building = "assembler"
 inputs = [
     {item = "steel_plate", amount = 2},
@@ -202,14 +202,14 @@ duration_seconds = 8.0
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "voidsteel_plate"
+id = "voidsteel_forging"
 building = "assembler"
 inputs = [{item = "voidsteel", amount = 1}, {item = "hardened_steel", amount = 1}]
 outputs = [{item = "voidsteel_plate", amount = 1}]
 duration_seconds = 8.0
 
 [[recipe]]
-id = "capital_core"
+id = "core_assembly"
 building = "assembler"
 inputs = [
     {item = "voidsteel", amount = 2},
@@ -223,25 +223,26 @@ duration_seconds = 10.0
 # Shortcut recipes — drop-only assembler recipes, gated by unlock groups in
 # unlocks.toml (REQ-LOCK-EXPLICIT). Pure rewards: item threat stays defined by
 # the base (expensive) path via the max rule, so shortcuts give real factory
-# efficiency without shifting any balance.
+# efficiency without shifting any balance. Named "direct_*" after the base
+# process they skip a step of, so the reward reads as what it is.
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "shortcut_steel_plate"
+id = "direct_rolling"
 building = "assembler"
 inputs = [{item = "iron_ore", amount = 3}]
 outputs = [{item = "steel_plate", amount = 1}]
 duration_seconds = 2.0
 
 [[recipe]]
-id = "shortcut_control_chip"
+id = "direct_etching"
 building = "assembler"
 inputs = [{item = "quartz", amount = 2}]
 outputs = [{item = "control_chip", amount = 1}]
 duration_seconds = 4.0
 
 [[recipe]]
-id = "shortcut_hardened_steel"
+id = "direct_hardening"
 building = "assembler"
 inputs = [{item = "iron_ingot", amount = 4}]
 outputs = [{item = "hardened_steel", amount = 1}]
@@ -252,35 +253,35 @@ duration_seconds = 8.0
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "drone_hull"
+id = "drone_framing"
 building = "assembler"
 inputs = [{item = "iron_ingot", amount = 1}]
 outputs = [{item = "drone_hull", amount = 1}]
 duration_seconds = 1.0
 
 [[recipe]]
-id = "frigate_hull"
+id = "frigate_framing"
 building = "assembler"
 inputs = [{item = "steel_plate", amount = 2}, {item = "copper_wire", amount = 1}]
 outputs = [{item = "frigate_hull", amount = 1}]
 duration_seconds = 2.0
 
 [[recipe]]
-id = "destroyer_hull"
+id = "destroyer_framing"
 building = "assembler"
 inputs = [{item = "steel_plate", amount = 3}, {item = "copper_coil", amount = 2}]
 outputs = [{item = "destroyer_hull", amount = 1}]
 duration_seconds = 4.0
 
 [[recipe]]
-id = "cruiser_hull"
+id = "cruiser_framing"
 building = "assembler"
 inputs = [{item = "hardened_steel", amount = 2}, {item = "control_chip", amount = 2}]
 outputs = [{item = "cruiser_hull", amount = 1}]
 duration_seconds = 6.0
 
 [[recipe]]
-id = "battlecruiser_hull"
+id = "battlecruiser_framing"
 building = "assembler"
 inputs = [
     {item = "hardened_steel", amount = 3},
@@ -291,7 +292,7 @@ outputs = [{item = "battlecruiser_hull", amount = 1}]
 duration_seconds = 8.0
 
 [[recipe]]
-id = "battleship_hull"
+id = "battleship_framing"
 building = "assembler"
 inputs = [
     {item = "voidsteel_plate", amount = 3},
@@ -302,7 +303,7 @@ outputs = [{item = "battleship_hull", amount = 1}]
 duration_seconds = 10.0
 
 [[recipe]]
-id = "dreadnought_hull"
+id = "dreadnought_framing"
 building = "assembler"
 inputs = [
     {item = "voidsteel_plate", amount = 5},
@@ -313,7 +314,7 @@ outputs = [{item = "dreadnought_hull", amount = 1}]
 duration_seconds = 12.0
 
 [[recipe]]
-id = "carrier_hull"
+id = "carrier_framing"
 building = "assembler"
 inputs = [
     {item = "voidsteel_plate", amount = 5},
@@ -328,21 +329,21 @@ duration_seconds = 12.0
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "railgun_s_module"
+id = "railgun_s_kit"
 building = "assembler"
 inputs = [{item = "copper_coil", amount = 1}]
 outputs = [{item = "railgun_s_module", amount = 1}]
 duration_seconds = 1.0
 
 [[recipe]]
-id = "salvager_module"
+id = "salvager_kit"
 building = "assembler"
 inputs = [{item = "steel_plate", amount = 1}, {item = "copper_wire", amount = 2}]
 outputs = [{item = "salvager_module", amount = 1}]
 duration_seconds = 2.0
 
 [[recipe]]
-id = "repair_tool_module"
+id = "repair_tool_kit"
 building = "assembler"
 inputs = [{item = "steel_plate", amount = 1}, {item = "copper_wire", amount = 2}]
 outputs = [{item = "repair_tool_module", amount = 1}]
@@ -350,56 +351,56 @@ duration_seconds = 2.0
 
 # Material-heavy, fast: the armor archetype.
 [[recipe]]
-id = "armor_plates_module"
+id = "armor_plates_kit"
 building = "assembler"
 inputs = [{item = "steel_plate", amount = 4}]
 outputs = [{item = "armor_plates_module", amount = 1}]
 duration_seconds = 3.0
 
 [[recipe]]
-id = "maneuvering_thrusters_module"
+id = "maneuvering_thrusters_kit"
 building = "assembler"
 inputs = [{item = "steel_plate", amount = 1}, {item = "copper_coil", amount = 1}]
 outputs = [{item = "maneuvering_thrusters_module", amount = 1}]
 duration_seconds = 2.0
 
 [[recipe]]
-id = "sensor_booster_module"
+id = "sensor_booster_kit"
 building = "assembler"
 inputs = [{item = "copper_wire", amount = 2}, {item = "copper_coil", amount = 1}]
 outputs = [{item = "sensor_booster_module", amount = 1}]
 duration_seconds = 2.0
 
 [[recipe]]
-id = "afterburner_module"
+id = "afterburner_kit"
 building = "assembler"
 inputs = [{item = "copper_coil", amount = 2}, {item = "steel_plate", amount = 1}]
 outputs = [{item = "afterburner_module", amount = 1}]
 duration_seconds = 3.0
 
 [[recipe]]
-id = "weapon_stabilizer_module"
+id = "weapon_stabilizer_kit"
 building = "assembler"
 inputs = [{item = "steel_plate", amount = 1}, {item = "copper_coil", amount = 1}]
 outputs = [{item = "weapon_stabilizer_module", amount = 1}]
 duration_seconds = 2.0
 
 [[recipe]]
-id = "weapon_primer_module"
+id = "weapon_primer_kit"
 building = "assembler"
 inputs = [{item = "capacitor_bank", amount = 1}, {item = "copper_coil", amount = 1}]
 outputs = [{item = "weapon_primer_module", amount = 1}]
 duration_seconds = 4.0
 
 [[recipe]]
-id = "weapon_upgrade_module"
+id = "weapon_upgrade_kit"
 building = "assembler"
 inputs = [{item = "control_chip", amount = 1}, {item = "copper_coil", amount = 1}]
 outputs = [{item = "weapon_upgrade_module", amount = 1}]
 duration_seconds = 4.0
 
 [[recipe]]
-id = "railgun_m_module"
+id = "railgun_m_kit"
 building = "assembler"
 inputs = [
     {item = "capacitor_bank", amount = 1},
@@ -410,7 +411,7 @@ outputs = [{item = "railgun_m_module", amount = 1}]
 duration_seconds = 4.0
 
 [[recipe]]
-id = "drone_bay_module"
+id = "drone_bay_kit"
 building = "assembler"
 inputs = [
     {item = "control_chip", amount = 1},
@@ -421,7 +422,7 @@ outputs = [{item = "drone_bay_module", amount = 1}]
 duration_seconds = 4.0
 
 [[recipe]]
-id = "railgun_l_module"
+id = "railgun_l_kit"
 building = "assembler"
 inputs = [
     {item = "capacitor_bank", amount = 1},
@@ -432,7 +433,7 @@ outputs = [{item = "railgun_l_module", amount = 1}]
 duration_seconds = 6.0
 
 [[recipe]]
-id = "drone_hangar_module"
+id = "drone_hangar_kit"
 building = "assembler"
 inputs = [
     {item = "voidsteel_plate", amount = 1},

bin/app/data/config/unlocks.toml

@@ -125,16 +125,16 @@ modules = ["drone_hangar"]
 # --- Assembler recipes -----------------------------------------------------
 
 [[unlock]]
-id = "shortcut_steel_plate"
+id = "direct_rolling"
 station_level = 1
-recipes = ["shortcut_steel_plate"]
+recipes = ["direct_rolling"]
 
 [[unlock]]
-id = "shortcut_control_chip"
+id = "direct_etching"
 station_level = 2
-recipes = ["shortcut_control_chip"]
+recipes = ["direct_etching"]
 
 [[unlock]]
-id = "shortcut_hardened_steel"
+id = "direct_hardening"
 station_level = 2
-recipes = ["shortcut_hardened_steel"]
+recipes = ["direct_hardening"]

bin/app/data/config/visuals.toml

@@ -109,40 +109,40 @@ glyph   = "E"
 # --- ores ---
 
 [items.iron_ore]
-fill    = "#8a5a4a"
-outline = "#201010"
+fill    = "#47271c"
+outline = "#a65b42"
 
 [items.copper_ore]
-fill    = "#c47a3a"
-outline = "#3a1a0a"
+fill    = "#deb592"
+outline = "#826a56"
 
 [items.quartz]
-fill    = "#e0d4f0"
-outline = "#40345a"
+fill    = "#4f3d66"
+outline = "#9776c4"
 
 # --- smelted basics ---
 
 [items.iron_ingot]
-fill    = "#b0b0b8"
-outline = "#202028"
+fill    = "#535357"
+outline = "#97979e"
 
 [items.copper_ingot]
-fill    = "#d48a4a"
-outline = "#402010"
+fill    = "#663810"
+outline = "#b07746"
 
 [items.silicon]
-fill    = "#33415e"
-outline = "#0e1420"
+fill    = "#737f99"
+outline = "#373f4f"
 
 # --- salvage loop ---
 
 [items.scrap]
-fill    = "#7a7268"
-outline = "#201a14"
+fill    = "#998e81"
+outline = "#574b3d"
 
 [items.voidsteel]
-fill    = "#4a3a6a"
-outline = "#151020"
+fill    = "#82759c"
+outline = "#3f374f"
 
 # --- basic components ---
 
@@ -151,106 +151,106 @@ fill    = "#e09a50"
 outline = "#3a2008"
 
 [items.steel_plate]
-fill    = "#8a92a0"
-outline = "#22262c"
+fill    = "#202836"
+outline = "#54698c"
 
 [items.copper_coil]
-fill    = "#d07030"
-outline = "#381808"
+fill    = "#cca287"
+outline = "#755d4d"
 
 [items.building_block]
-fill    = "#c8b070"
-outline = "#302810"
+fill    = "#544724"
+outline = "#a18845"
 
 # --- advanced components ---
 
 [items.control_chip]
-fill    = "#2ea35a"
-outline = "#0a2a14"
+fill    = "#74b08b"
+outline = "#42634e"
 
 [items.capacitor_bank]
 fill    = "#d0a030"
 outline = "#302408"
 
 [items.hardened_steel]
-fill    = "#6a7280"
-outline = "#181c22"
+fill    = "#818999"
+outline = "#3e4859"
 
 [items.ceramic_plate]
 fill    = "#e0d8c8"
 outline = "#3a3428"
 
 [items.drive_unit]
-fill    = "#4a6ad0"
-outline = "#101a38"
+fill    = "#92a4de"
+outline = "#545f80"
 
 # --- capital components ---
 
 [items.voidsteel_plate]
-fill    = "#7a5aaa"
-outline = "#1c1038"
+fill    = "#9986b5"
+outline = "#544766"
 
 [items.capital_core]
-fill    = "#b040d0"
-outline = "#280c30"
+fill    = "#420c52"
+outline = "#9444ab"
 
 # --- module items ---
 
 [items.railgun_s_module]
-fill    = "#691313"
-outline = "#f3ff4f"
+fill    = "#bf7e7e"
+outline = "#664343"
 
 [items.railgun_m_module]
-fill    = "#892020"
-outline = "#f3ff4f"
+fill    = "#b07474"
+outline = "#593b3b"
 
 [items.railgun_l_module]
-fill    = "#a92d2d"
-outline = "#f3ff4f"
+fill    = "#b07474"
+outline = "#593b3b"
 
 [items.salvager_module]
 fill    = "#b2cfdd"
 outline = "#236137"
 
 [items.repair_tool_module]
-fill    = "#2e9ba3"
-outline = "#689275"
+fill    = "#0b4347"
+outline = "#38868c"
 
 [items.armor_plates_module]
-fill    = "#808080"
-outline = "#202020"
+fill    = "#999999"
+outline = "#545454"
 
 [items.sensor_booster_module]
-fill    = "#40a0ff"
-outline = "#102840"
+fill    = "#a0c9f2"
+outline = "#607991"
 
 [items.maneuvering_thrusters_module]
-fill    = "#5090e0"
-outline = "#142438"
+fill    = "#92b4de"
+outline = "#566982"
 
 [items.afterburner_module]
-fill    = "#6080c0"
-outline = "#182030"
+fill    = "#1d2e52"
+outline = "#486db5"
 
 [items.weapon_upgrade_module]
 fill    = "#ff4040"
 outline = "#401010"
 
 [items.weapon_primer_module]
-fill    = "#e03838"
-outline = "#380e0e"
+fill    = "#e69797"
+outline = "#855858"
 
 [items.weapon_stabilizer_module]
-fill    = "#c03030"
-outline = "#300c0c"
+fill    = "#c78383"
+outline = "#6e4848"
 
 [items.drone_bay_module]
 fill    = "#cc66ff"
 outline = "#331040"
 
 [items.drone_hangar_module]
-fill    = "#9933cc"
-outline = "#260c33"
+fill    = "#8c689e"
+outline = "#42314a"
 
 # --- ship hulls (outline matches the ship's fleet color in [ships.*]) ---
 
@@ -283,8 +283,8 @@ fill    = "#1b1b1b"
 outline = "#ff5533"
 
 [items.carrier_hull]
-fill    = "#1b1b1b"
-outline = "#cc66ff"
+fill    = "#310f42"
+outline = "#8542a6"
 
 # -----------------------------------------------------------------------------
 # Ships
@@ -344,10 +344,12 @@ width_px      = 2
 [overlays]
 ghost_valid    = "#ffffff44"   # builder-mode ghost, placement allowed (REQ-BLD-GHOST)
 ghost_invalid  = "#ff000044"   # builder-mode ghost, placement invalid (REQ-BLD-PLACE-VALID)
-deconstruct_tint  = "#ff000033"   # deconstruct-mode hover tint
-selection_rect = "#00ff00"     # box-drag selection rectangle (REQ-UI-MULTI-SELECT)
+deconstruct_tint  = "#ff000033"   # deconstruct-mode hover tint; its RGB also draws the
+                                  # box-drag rectangle in deconstruct mode, opaque
+                                  # (REQ-UI-MULTI-SELECT, REQ-BLD-DECONSTRUCT-BOX)
 tile_highlight = "#ffffff22"   # tile under cursor
-selected_outline = "#ffff00"   # outline drawn around currently-selected building(s)
+selected_outline = "#ffff00"   # outline around currently-selected building(s), and the
+                               # box-drag selection rectangle (REQ-UI-MULTI-SELECT)
 config_transfer = "#33ccff66"  # blueprint ghost over a configuration-transfer target (REQ-UI-BLUEPRINT-TRANSFER)
 locked_asteroid = "#0000007f"  # tint over the asteroid left of the buildable edge (not yet unlocked by expansion)
 modal_dim      = "#00000099"   # semi-transparent black dim behind modal dialogs/menus (REQ-UI-MODAL-DIM)

bin/app/data/config/world.toml

@@ -1,5 +1,5 @@
 [world]
-height_tiles = 40
+height_tiles = 30
 refund_percentage = 100
 deconstruction_time_seconds = 0.1
 starting_building_blocks = 200
@@ -15,7 +15,7 @@ building_blocks_tooltip = "Building blocks are the currency for construction. Sp
 artifact_tooltip = "Artifacts are the key to victory. Earn one by choosing the artifact reward when you destroy a set of enemy defence stations. Collect enough of them to win the game."
 
 [regions]
-asteroid_width_tiles = 60
+asteroid_width_tiles = 40
 player_buffer_width_tiles = 20
 contest_zone_width_tiles = 60
 enemy_buffer_width_tiles = 20

bin/test/data/config/recipes.toml

@@ -75,20 +75,17 @@ building = "reprocessing_plant"
 inputs = [{item = "scrap", amount = 5}]
 duration_seconds = 3.0
 
-  [[recipe.outputs]]
-  item = "iron_ingot"
-  amount = 2
+  [[recipe.output_group]]
   probability = 0.6
+  items = [{item = "iron_ingot", amount = 2}]
 
-  [[recipe.outputs]]
-  item = "circuit_board"
-  amount = 1
+  [[recipe.output_group]]
   probability = 0.3
+  items = [{item = "circuit_board", amount = 1}]
 
-  [[recipe.outputs]]
-  item = "advanced_alloy"
-  amount = 1
+  [[recipe.output_group]]
   probability = 0.1
+  items = [{item = "advanced_alloy", amount = 1}]
 
 # -------------------------------------------------------------------
 # Extra recipes for ThreatCostCalculator unit tests (fixes 6-9)

docs/architecture.md

@@ -124,12 +124,31 @@ Within a single simulation tick, subsystems run in this fixed order. The order i
 Three product targets plus tests:
 
 - `lib/` — simulation + config. Depends on Qt Core + Qt Gui, toml++, tinyexpr. No QtWidgets.
-- `ui/` — QtWidgets + `QOpenGLWidget` code: header bar, game world view, selected building panel, build button bar. Depends on `lib` and on Qt's OpenGL widgets module.
+- `ui/` — QtWidgets + `QOpenGLWidget` code: header bar, game world view, selection panel, build button bar, controls panel. Depends on `lib` and on Qt's OpenGL widgets module.
+  - `ui/selection/` — the selection panel's contents. `SelectionPanel` itself only arbitrates between the two selection categories, picks a card from the catalog (`SelectionContentFactory`), and hosts one at a time; each kind of selection has its own `SelectionContent` subclass assembled from shared parts (REQ-UI-SELECTION-CARD, REQ-UI-SELECTION-CONTENT).
 - `app/` — thin `main()` that creates the simulation, the UI, and wires them together. Depends on `ui`.
 - `tests/` — Catch2 tests. Links only against `lib`.
 
 Directory discipline inside `lib/` keeps the internal sim/config seam clear; sim code must not reach into config parsing and vice versa.
 
+## Player Input
+
+Every player control is declared once, in `lib/core/ControlAction.h`, and read by three consumers that must never disagree about it:
+
+* **`ControlsPanel`** asks which actions apply and draws a row per action (REQ-UI-CONTROLS-CONTENT).
+* **`InputMapper`** resolves a key press to an action and fires the event that action stands for.
+* **`GameWorldView`** resolves a mouse gesture to an action and runs the branch that carries it out.
+
+The file declares; it never performs. It holds no simulation access, fires no events, and names nothing — display strings live in `ui/ControlActionText.h`, which renders each badge from the binding the resolver actually matches, so a chip cannot claim a key that does nothing. What an action *does* stays in the widget that always did it: the drag state machines, hit-testing, and command enqueuing were not moved.
+
+Three invariants are easy to break here:
+
+* **Do not add a shortcut straight to `InputMapper`'s switch or `mousePressEvent`'s branches.** Add the action and its binding to the table; the handler switches on the resolved action. A binding added directly is invisible to the panel, which is the drift the table exists to prevent. (Build hotkeys and `F3`/`F4` are deliberate exceptions, documented in the header and in REQ-UI-CONTROLS-ACCURACY.)
+* **Availability and display are different questions.** An action can be live in a context the panel does not advertise it in — `Ctrl`+click with an empty selection is the standing example. `isControlActionAvailable` answers the first, the per-context row lists answer the second, and `ControlActionTest` asserts the pairing that matters: every row's bindings resolve back to that row's action.
+* **Gesture state is shared, not owned by an action.** Whether a belt drag is in progress decides what the right mouse button means, so it lives on `BuildModeController` where the resolver can see it — as does the hovered-transfer flag. `m_boxSelecting` is likewise one gesture serving two actions (box select and deconstruct area).
+
+`ControlContext` is a plain snapshot rather than references to the live controllers, which is what keeps the rules testable without a world and stops an action reaching into the simulation: if a rule needs a fact, the fact is named in the struct and the caller supplies it. When bindings become player-configurable, only the binding tables in `ControlAction.cpp` turn from hard-coded data into loaded data.
+
 ## Belt Subsystem
 
 Belts and splitters are their own specialized subsystem. Belt items are **not** entities — they are transient data flowing through the belt representation. They do not have identities that persist across ticks.
@@ -408,7 +427,7 @@ width_px = 2
 ghost_valid    = "#ffffff44"
 ghost_invalid  = "#ff000044"
 deconstruct_tint  = "#ff000033"
-selection_rect = "#00ff00"
+selected_outline = "#ffff00"
 
 [toast]
 bg        = "#000000cc"

docs/balancing/derived.md

@@ -44,9 +44,9 @@ move. Combat stats were tuned empirically against the arena suite in
 | capital_core | 2 voidsteel + 1 capacitor_bank + 1 control_chip | 10 | 1 | 240 |
 
 Shortcut recipes (drop-only; item threat stays defined by the base path
-via the max rule): `shortcut_steel_plate` 3 iron_ore → 1 plate (2 s,
-level 1), `shortcut_control_chip` 2 quartz → 1 chip (4 s, level 2),
-`shortcut_hardened_steel` 4 iron_ingot → 1 hardened (8 s, level 2).
+via the max rule): `direct_rolling` 3 iron_ore → 1 plate (2 s,
+level 1), `direct_etching` 2 quartz → 1 chip (4 s, level 2),
+`direct_hardening` 4 iron_ingot → 1 hardened (8 s, level 2).
 
 Ratio curve realized: t1 all 1:1 (miner:smelter); t2 clean 2:3
 (ingot→plate, wire→coil); t3 strange — 2:5 (silicon→chip), 3:5
@@ -122,13 +122,13 @@ range 120, scrap 40. Enemy station: 3000+1500x HP, 25+12x dmg,
 ## Pacing
 
 **Unlock ladder** (level → unlocks; ← marks `unlock_requires`; starting
-set at −1: drone, frigate, railgun_s, salvager, building_block recipe):
+set at −1: drone, frigate, railgun_s, salvager, block_pressing recipe):
 
 | level | ships | modules | recipes |
 |---|---|---|---|
 | 0 | destroyer | repair_tool, armor_plates | |
-| 1 | | maneuvering_thrusters, sensor_booster | shortcut_steel_plate |
-| 2 | cruiser | railgun_m, afterburner | shortcut_control_chip, shortcut_hardened_steel |
+| 1 | | maneuvering_thrusters, sensor_booster | direct_rolling |
+| 2 | cruiser | railgun_m, afterburner | direct_etching, direct_hardening |
 | 3 | | weapon_stabilizer | |
 | 4 | battlecruiser ← cruiser | weapon_primer, weapon_upgrade | |
 | 5 | | drone_bay | |

docs/balancing/rules.md

@@ -230,8 +230,8 @@ supporting different fleet doctrines feel structurally different to build.
   **smelting** (same basic materials as ore — the safe, boring option) and
   **reprocessing** (probabilistic higher intermediates, including the
   late-game input — the gamble that eventually becomes mandatory).
-- The reprocessing output pool renormalizes over implicitly unlocked items
-  (REQ-LOCK-REPROCESSING-POOL), so its output quality improves
+- The reprocessing output pool renormalizes over the output groups whose items
+  are implicitly unlocked (REQ-LOCK-OUTPUT-POOL), so its output quality improves
   automatically as the run progresses. **Rule:** weights are authored for
   the *fully unlocked* pool state; early-game behavior falls out of
   renormalization for free and needs no separate staging.

docs/replay_design.md

@@ -390,11 +390,11 @@ Reshape mutations to flow through one path; behaviour unchanged.
   before the tick batch (runs even at 0× → build-while-paused preserved). A drained `Reset`
   triggers the view reset.
 - Refactored every UI mutation site: `GameWorldView` owns the `CommandManager` and enqueues
-  directly; `MainWindow` and `SelectedBuildingPanel` emit `CommandRequestedEvent` (carrying a
+  directly; `MainWindow` and `SelectionPanel` emit `CommandRequestedEvent` (carrying a
   `shared_ptr<const Command>`) which `GameWorldView` subscribes to and enqueues.
 - **Files:** new `lib/sim/Command.h`, `CommandManager.{h,cpp}`; `CommandRequestedEvent.h`;
   `Simulation.{h,cpp}` (`apply`); `GameWorldView.{h,cpp}`, `MainWindow.cpp`,
-  `SelectedBuildingPanel.cpp`; new `CommandTest.cpp`.
+  `SelectionPanel.cpp`; new `CommandTest.cpp`.
 - **Exit criteria:** game plays identically (including build-while-paused); determinism test
   still passes; `[command]` equivalence tests pass; no production call site can mutate the sim
   directly (compile-enforced: the `Simulation` mutators are private, tests excepted via

docs/requirements.md

@@ -6,8 +6,7 @@ Config files use the TOML format. The following config files drive game paramete
 
 - **world.toml** — world dimensions, region widths, expansion amounts, building refund percentage, building deconstruction time, wave timing, boss wave timing, belt speed, starting building blocks, departure interval, ship orbit factor, rally orbit radius, scrap-per-threat conversion, combat target-selection parameters (target score formula, overclaim penalty formula, target hysteresis), artifact chance formula, artifact win count, view pan speeds (slow and fast horizontal pan speed and pan ramp band width), an optional building blocks tooltip string (shown as the header bar's building blocks stock hover tooltip, REQ-UI-BLOCKS-TOOLTIP; omitted when unset), and an optional artifact tooltip string (shown as the header bar's artifact count hover tooltip, REQ-UI-ARTIFACTS-TOOLTIP; omitted when unset).
 - **buildings.toml** — building block cost and construction time per building type, plus an optional tooltip description string per building type (shown as the build button's hover tooltip, REQ-UI-BUILD-TOOLTIP; omitted when unset). Whether a building type is available from game start or must be unlocked during play is not defined here but in **unlocks.toml** (REQ-LOCK-EXPLICIT): a building type granted by an unlock group starts locked and is hidden from the build menu until its group is awarded (REQ-LOCK-BUILDING).
-- **recipes.toml** — crafting recipes: inputs, outputs, quantities, durations, and reprocessing plant probabilities. Assembler recipe entries may optionally define `unlocked_at_start` (boolean, default false): when true the recipe is available from game start regardless of the implicit item graph — used for base recipes that no schematic's materials reach (such as building blocks; see REQ-LOCK-IMPLICIT). Which assembler recipes must instead be awarded during play (explicitly gated) is defined in **unlocks.toml**, not here (REQ-LOCK-EXPLICIT); every remaining assembler recipe is implicitly unlocked through the item graph (REQ-LOCK-IMPLICIT). Any recipe entry may optionally define `icon` (string): the id of an item whose icon represents the recipe in the recipe-selection dialog (REQ-UI-RECIPE-ICON); when omitted, the recipe's first output item is used.
-- **ships.toml** — per schematic: a human-readable display name (used in the UI), hull stats (HP, max linear speed, sensor range, main acceleration, maneuvering acceleration, angular acceleration, max rotation speed) as plain values, required build materials, a layout grid defining the ship's module slots, and a `default_modules` list used for enemy wave ships (see REQ-WAV-DEFAULT-MODULES). Whether a ship schematic is available from game start or must be unlocked during play is defined in **unlocks.toml** (REQ-LOCK-EXPLICIT), not here.
+- **recipes.toml** — crafting recipes: inputs, output groups with their quantities and probability weights, and durations (REQ-MAT-OUTPUT-GROUP). Assembler recipe entries may optionally define `unlocked_at_start` (boolean, default false): when true the recipe is available from game start regardless of the implicit item graph — used for base recipes that no schematic's materials reach (such as building blocks; see REQ-LOCK-IMPLICIT). Which assembler recipes must instead be awarded during play (explicitly gated) is defined in **unlocks.toml**, not here (REQ-LOCK-EXPLICIT); every remaining assembler recipe is implicitly unlocked through the item graph (REQ-LOCK-IMPLICIT).- **ships.toml** — per schematic: a human-readable display name (used in the UI), hull stats (HP, max linear speed, sensor range, main acceleration, maneuvering acceleration, angular acceleration, max rotation speed) as plain values, required build materials, a layout grid defining the ship's module slots, and a `default_modules` list used for enemy wave ships (see REQ-WAV-DEFAULT-MODULES). Whether a ship schematic is available from game start or must be unlocked during play is defined in **unlocks.toml** (REQ-LOCK-EXPLICIT), not here.
 - **modules.toml** — per module type: id, surface mask, materials list, production time, fill color, glyph, an optional tooltip description string (shown as the module selection button's hover tooltip, REQ-MOD-UI-MODULE-TOOLTIP; omitted when unset), and an optional capability section and/or stat modifier formulas. Whether a module schematic is available from game start or must be unlocked during play is defined in **unlocks.toml** (REQ-LOCK-EXPLICIT), not here. A module with a capability section (`[module.weapon]`, `[module.salvage]`, or `[module.repair]`) containing base stat formulas is a **capability module** that grants the ship a weapon, salvage bay, or repair tool per instance (see REQ-MOD-CONFIG for the full list of formulas per capability type). A module with only `added_*`/`multiplied_*` formulas is a **passive module** that modifies stats on the ship or on capability module instances (see REQ-MOD-STAT-CALC).
 - **unlocks.toml** — unlock groups: each `[[unlock]]` entry names a group of ship schematics, module schematics, building types, and/or assembler recipes that are awarded together from a single defence station drop (see Unlock Group Format, REQ-LOCK-EXPLICIT, REQ-DEF-SCHEMATIC-DROP). Anything not granted by any unlock group is available from game start.
 - **stations.toml** — HP, damage, range, fire rate, and scrap drop for player and enemy defence stations, defined as formulas of station level.
@@ -91,7 +90,7 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 ## Game World
 
 - REQ-GW-COORDS: Tile coordinates are integer `(x, y)`. The origin `(0, 0)` is the first column of space — the tile immediately to the right of the asteroid's right edge at game start, at the top of the world. X grows right; Y grows down. All asteroid tiles have `x < 0`; asteroid left-expansions add tiles at increasingly negative X. The origin never shifts.
-- REQ-GW-TILE-SIZE: Tiles are square. The tile size in pixels is derived automatically so that the world height (in tiles) exactly fills the game world view's height in pixels. Items on belts are rendered at half-tile size (drawn as an item icon, or a colored square as the fallback — REQ-UI-ITEM-ICON); when multiple items occupy the same tile they are spaced quarter-tile apart along the direction of travel and overlap, rendered in ascending order of progress — the least-progressed item is drawn first (bottom) and the furthest-progressed item is drawn last (on top). Items emerging from a building's output port are rendered by these same rules on that port's output belt (REQ-MAT-OUTPUT-EMERGE).
+- REQ-GW-TILE-SIZE: Tiles are square. The tile size in pixels is derived automatically so that the world height (in tiles) exactly fills the game world view's height in pixels. Items on belts are rendered at half-tile size (drawn as a colored square carrying the item's icon, or the square alone when the item has no icon — REQ-UI-ITEM-ICON); when multiple items occupy the same tile they are spaced quarter-tile apart along the direction of travel and overlap, rendered in ascending order of progress — the least-progressed item is drawn first (bottom) and the furthest-progressed item is drawn last (on top). Items emerging from a building's output port are rendered by these same rules on that port's output belt (REQ-MAT-OUTPUT-EMERGE).
 - REQ-GW-BELT-CAPACITY: Belt tiles and tunnel entry/exit tiles each hold up to four items simultaneously, queued one behind the other in the direction of travel. Splitter tiles hold up to four items: two unassigned items (progress < 0.5, not yet routed to an output) and one item per output slot (progress ≥ 0.5, committed to a specific output direction). Output-slot items are rendered on top of unassigned items; when both output slots are occupied, their rendering order follows the clockwise port order starting from East.
 - REQ-GW-BELT-SPEED: Items on belts move at `world.toml [world].belt_speed_tiles_per_second` tiles per second (default 2).
 - REQ-GW-HEIGHT: The world height (in tiles) is read from `world.toml [world].height_tiles`.
@@ -123,8 +122,8 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 - REQ-BLD-COST: The player places buildings from a build menu. Placement costs building blocks from the global stock. The cost per building type is read from `buildings.toml [[building]].cost`.
 - REQ-BLD-QUEUE: Placed buildings enter a construction queue and are built one at a time. Each building takes a duration defined in `buildings.toml [[building]].construction_time_seconds` to construct.
 - REQ-BLD-ASTEROID-ONLY: Buildings can only be placed on asteroid tiles (per surface_mask; tiles marked `S` may extend into space).
-- REQ-BLD-BUILDER-MODE: Clicking a build button activates builder mode for that building type. Builder mode is exited by right-clicking in the game world or clicking the same build button again. (Exception: while a belt drag placement is in progress, right-clicking cancels that drag instead of exiting, and builder mode stays active — REQ-BLD-BELT-DRAG.)
-- REQ-BLD-GHOST: While in builder mode, a ghost of the building is rendered at the tile under the cursor, showing where it would be placed. The ghost is drawn semi-transparently in the building type's own visuals — its `fill` and `outline` colors and `glyph` from `visuals.toml` — so that different building types are visually distinguishable in builder mode rather than all looking alike. When the current cursor position is invalid, the ghost instead uses the distinct "invalid" color (REQ-BLD-PLACE-VALID), which overrides the per-building coloring.
+- REQ-BLD-BUILDER-MODE: Clicking a build button activates builder mode for that building type, clearing the selection as entering any build mode does (REQ-UI-SELECTION-EXCLUSIVE). Builder mode is exited by right-clicking in the game world or clicking the same build button again. (Exception: while a belt drag placement is in progress, right-clicking cancels that drag instead of exiting, and builder mode stays active — REQ-BLD-BELT-DRAG.)
+- REQ-BLD-GHOST: While in builder mode, a ghost of the building is rendered at the tile under the cursor, showing where it would be placed. The ghost follows the tile the cursor points at, which includes the view scrolling (REQ-UI-SCROLL) under a cursor that has not moved: the ghost then moves across the world with the scroll rather than sticking to the tile it was last placed on by a mouse move, exactly as a running selection box does (REQ-UI-MULTI-SELECT). The same holds for everything else the hovered position determines — placement validity (REQ-BLD-PLACE-VALID), the tunnel end being placed (REQ-BLD-TUNNEL-MODE), a belt drag's path (REQ-BLD-BELT-DRAG), the blueprint ghost (REQ-UI-BLUEPRINT-MODE), and the deconstruct hover (REQ-UI-DECONSTRUCT-BUTTON). A cursor that is not over the game world — resting on one of the floating panels (REQ-UI-CONTROLS-PANEL, REQ-UI-BUILD-BAR, REQ-UI-SELECTION-PANEL), or outside the window — points at no tile and therefore hovers nothing: no builder ghost and no blueprint ghost is drawn, no tunnel connection is previewed, and no building is tinted as the deconstruct hover, until the cursor returns to the world. The mode itself is unaffected — the player is still building, just not over anything — and the position the ghost had is not remembered: it is re-derived from wherever the cursor comes back. This applies whenever the cursor points elsewhere, including at the moment a mode is entered, so a mode entered from a build button (REQ-UI-BUILD-BAR) shows its ghost only once the cursor is over the world, while one entered by hotkey (REQ-UI-HOTKEYS) under a cursor already there shows it at once. The one exception is a gesture that holds the mouse button — a belt drag (REQ-BLD-BELT-DRAG) or a selection or deconstruct box (REQ-UI-MULTI-SELECT, REQ-BLD-DECONSTRUCT-BOX) — which goes on following the cursor across the panels and beyond the window until the button is released. The ghost is drawn semi-transparently in the building type's own visuals — its `fill` and `outline` colors and `glyph` from `visuals.toml` — so that different building types are visually distinguishable in builder mode rather than all looking alike. When the current cursor position is invalid, the ghost instead uses the distinct "invalid" color (REQ-BLD-PLACE-VALID), which overrides the per-building coloring.
 - REQ-BLD-ROTATE: While in builder mode, pressing Shift+R rotates the ghost 90° clockwise and R rotates it 90° counter-clockwise. Rotation affects the direction of the output port.
 - REQ-BLD-PLACE: Clicking a valid tile in builder mode places a construction site and adds it to the build queue, consuming building blocks from the global stock. (For belts, placement is instead deferred to a drag gesture and happens on mouse release — REQ-BLD-BELT-DRAG.)
 - REQ-BLD-PLACE-VALID: A placement position is valid only if (a) every footprint cell in the rotated `surface_mask` is satisfied by the underlying terrain — `A` cells coincide with asteroid tiles, `S` cells coincide with space tiles — (b) no footprint cell overlaps an existing placed building or construction site, except as allowed by REQ-BLD-ROTATE-IN-PLACE (builder mode) or REQ-UI-BLUEPRINT-OVERLAP and REQ-UI-BLUEPRINT-TRANSFER (blueprint placement mode), and (c) the player has enough building blocks to afford the building. The ghost (REQ-BLD-GHOST) is rendered in a distinct "invalid" color — overriding its per-building coloring (REQ-BLD-GHOST) — when the current cursor position fails any of these conditions.
@@ -145,19 +144,23 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 - REQ-BLD-DECONSTRUCT: The player can deconstruct a placed factory building. Deconstructing a **fully-built** factory building does not remove it instantly: it is added to the deconstruction queue (REQ-BLD-DECON-QUEUE) and, once its deconstruction completes, `world.toml [world].refund_percentage` percent of the original building block cost (default 75%) is returned to the global stock. Exception: if the building is still in the construction queue (not yet fully built, including the one currently being constructed), it is **not** queued for deconstruction but removed instantly from the construction queue, and the **full** building block cost is refunded immediately. The HQ and player defence stations cannot be deconstructed.
 - REQ-BLD-DECON-QUEUE: Fully-built factory buildings marked for demolition (REQ-BLD-DECONSTRUCT) enter a **deconstruction queue** that is processed one building at a time and runs in parallel with the construction queue (REQ-BLD-QUEUE) — the two queues advance independently and simultaneously. Each building takes `world.toml [world].deconstruction_time_seconds` (default 0.1) to deconstruct, the same duration for every building type. When a building's deconstruction completes it is removed from the world and its refund is credited (REQ-BLD-DECONSTRUCT). A building **stops operating the moment it enters the queue**: it runs no production and transports no items, and no longer participates as a live building (its tunnel pairing is re-evaluated as if it were gone, REQ-BLD-TUNNEL-PAIR), but it still physically occupies its tiles until removed, so those tiles stay blocked for placement. A queued building can be taken back out of the deconstruction queue before it is removed (REQ-BLD-DECONSTRUCT-CLICK, REQ-BLD-DECONSTRUCT-BOX) — including the one currently being deconstructed; doing so discards any deconstruction progress, credits no refund, and the building resumes operating (and re-pairs, REQ-BLD-TUNNEL-PAIR). Construction sites never enter the deconstruction queue (REQ-BLD-DECONSTRUCT). Every building in the deconstruction queue is rendered with the deconstruct tint — the `visuals.toml [overlays].deconstruct_tint` color, the same tint applied to a building hovered in deconstruct mode (REQ-UI-DECONSTRUCT-BORDER) — so queued buildings are visually distinct.
 - REQ-BLD-DECONSTRUCT-CLICK: While in deconstruct mode (REQ-UI-HOTKEYS, REQ-UI-DECONSTRUCT-BUTTON), left-clicking a placed factory building or construction site in the game world marks it for demolition, following the rules of REQ-BLD-DECONSTRUCT: a fully-built building is added to the deconstruction queue (REQ-BLD-DECON-QUEUE), and a construction site is removed instantly with the full refund. Left-clicking a fully-built building that is **already in the deconstruction queue** instead removes it from the queue (un-queues it, REQ-BLD-DECON-QUEUE), with no refund; repeated clicks on the same building therefore alternate between queueing and un-queueing it. Clicking a building that cannot be deconstructed (the HQ or a player defence station, per REQ-BLD-DECONSTRUCT), or clicking empty world space, has no effect. Deconstruct mode stays active after each action so the player can continue without re-entering the mode; it is exited via the Q toggle (REQ-UI-HOTKEYS) or the Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON).
-- REQ-BLD-DECONSTRUCT-BOX: While in deconstruct mode (REQ-UI-HOTKEYS, REQ-UI-DECONSTRUCT-BUTTON), the player can click and drag a selection box in the game world. A selection rectangle is drawn while dragging, using the same box-drag gesture and coverage semantics as the multi-select box (REQ-UI-MULTI-SELECT). On mouse up, following the rules of REQ-BLD-DECONSTRUCT: every construction site covered by the box is removed instantly with the full refund; and among the fully-built deconstructible buildings covered by the box, if **all** of them are already in the deconstruction queue they are all removed from it (un-queued, REQ-BLD-DECON-QUEUE), otherwise every covered building not yet in the queue is added to the deconstruction queue (already-queued ones stay). Buildings that cannot be deconstructed (the HQ and player defence stations, per REQ-BLD-DECONSTRUCT) are excluded from the box demolition; ships and defence stations are never affected.
-- REQ-BLD-SITE-CONFIG: A construction site — a building that has been placed but is still queued or under construction (REQ-BLD-QUEUE) — can be selected and configured exactly like the equivalent operational building, before it finishes building. Whatever configuration the building type supports is available on the site: the recipe for a Miner or Assembler (REQ-UI-SELECT-BUTTON), the produced-ship schematic and its module layout for a Shipyard (REQ-UI-SELECT-BUTTON, REQ-MOD-UI-PREVIEW, REQ-MOD-UI-DIALOG), and the output filters for a Splitter (REQ-BLD-SPLITTER) — all set through the same Selected Building Panel controls (REQ-UI-CONFIG-INLINE). Only currently unlocked recipes and schematics are offered, exactly as for operational buildings (REQ-LOCK-UI-RECIPE, REQ-LOCK-UI-SCHEMATIC, REQ-LOCK-UI-SPLITTER). The configuration is stored on the construction site and carries over unchanged when construction completes, so the building becomes operational already configured. A construction site has no input/output buffers and runs no production cycle, so the buffer and production-progress portions of the panel (REQ-UI-SINGLE-SELECTION, REQ-UI-PRODUCTION-PROGRESS) are not shown for it; only its construction progress (REQ-UI-CONSTRUCTION-PROGRESS) and its configuration controls appear. (Blueprint placement already applies a stored recipe or schematic to a construction site on placement per REQ-UI-BLUEPRINT-PLACE; this requirement additionally lets the player set or change that configuration directly on an existing site.)
+- REQ-BLD-DECONSTRUCT-BOX: While in deconstruct mode (REQ-UI-HOTKEYS, REQ-UI-DECONSTRUCT-BUTTON), the player can click and drag a selection box in the game world. A selection rectangle is drawn while dragging, using the same box-drag gesture and coverage semantics as the multi-select box (REQ-UI-MULTI-SELECT), but drawn in the deconstruct color rather than the ordinary selection color (REQ-UI-MULTI-SELECT, Rectangle color). On mouse up, following the rules of REQ-BLD-DECONSTRUCT: every construction site covered by the box is removed instantly with the full refund; and among the fully-built deconstructible buildings covered by the box, if **all** of them are already in the deconstruction queue they are all removed from it (un-queued, REQ-BLD-DECON-QUEUE), otherwise every covered building not yet in the queue is added to the deconstruction queue (already-queued ones stay). Buildings that cannot be deconstructed (the HQ and player defence stations, per REQ-BLD-DECONSTRUCT) are excluded from the box demolition; ships and defence stations are never affected.
+- REQ-BLD-SITE-CONFIG: A construction site — a building that has been placed but is still queued or under construction (REQ-BLD-QUEUE) — can be selected and configured exactly like the equivalent operational building, before it finishes building. Whatever configuration the building type supports is available on the site: the recipe for a Miner, Assembler, Smelter or Reprocessing Plant (REQ-UI-SELECT-BUTTON, REQ-BLD-AUTO-RECIPE), the produced-ship schematic and its module layout for a Shipyard (REQ-UI-SELECT-BUTTON, REQ-MOD-UI-PREVIEW, REQ-MOD-UI-DIALOG), and the output filters for a Splitter (REQ-BLD-SPLITTER) — all set through the same selection panel controls (REQ-UI-CONFIG-INLINE). Only currently unlocked recipes and schematics are offered, exactly as for operational buildings (REQ-LOCK-UI-RECIPE, REQ-LOCK-UI-SCHEMATIC, REQ-LOCK-UI-SPLITTER). The configuration is stored on the construction site and carries over unchanged when construction completes, so the building becomes operational already configured. A construction site has no input/output buffers and runs no production cycle, so the buffer and production-progress portions of the panel (REQ-UI-SINGLE-SELECTION, REQ-UI-PRODUCTION-PROGRESS) are not shown for it; only its construction progress (REQ-UI-CONSTRUCTION-PROGRESS) and its configuration controls appear. (Blueprint placement already applies a stored recipe or schematic to a construction site on placement per REQ-UI-BLUEPRINT-PLACE; this requirement additionally lets the player set or change that configuration directly on an existing site.)
 
 ## Building Types
 
 - REQ-BLD-MINER: **Miner** (2×2): The player selects which ore type it extracts. Each ore type corresponds to a `recipes.toml [[recipe]]` entry with `building = "miner"`, defining the output item and `duration_seconds`. Every asteroid tile is equivalent for mining — any miner can produce any ore type based solely on its selected recipe. Ore never depletes. Only implicitly unlocked ore-type recipes are available for selection (REQ-LOCK-UI-RECIPE).
-- REQ-BLD-SMELTER: **Smelter** (2×2): Converts ore or scrap into basic materials. No recipe selection required. Inputs, outputs, and rates are defined in `recipes.toml [[recipe]]` entries with `building = "smelter"`.
-- REQ-BLD-ASSEMBLER: **Assembler** (3×3): The player selects a recipe from the config-defined crafting tree. Produces the selected output item at the rate defined in the corresponding `recipes.toml [[recipe]]` entry with `building = "assembler"`. Only implicitly unlocked recipes are available for selection (REQ-LOCK-UI-RECIPE).
-- REQ-BLD-REPROCESSING: **Reprocessing Plant** (3×3): Consumes scrap per cycle and produces exactly one higher-level intermediate product per cycle via weighted random pick. The input quantity, possible output items, per-output weights, and amounts are defined in `recipes.toml [[recipe]]` entries with `building = "reprocessing_plant"` (`inputs`, `outputs[].item`, `outputs[].amount`, `outputs[].weight`). Weights are normalized at load time; their sum does not need to equal 1. The output is rolled at cycle start (see REQ-MAT-CYCLE); the pool of eligible outputs is restricted to implicitly unlocked item types (REQ-LOCK-REPROCESSING-POOL). The output buffer holds at most one cycle's output — see REQ-MAT-OUTPUT-BUFFER-REPROCESSING.
+- REQ-BLD-SMELTER: **Smelter** (2×2): Converts ore or scrap into basic materials. Its recipe is selected as any other building's is, except that it also picks one for itself from the first material it is offered (REQ-BLD-AUTO-RECIPE). Inputs, outputs, and rates are defined in `recipes.toml [[recipe]]` entries with `building = "smelter"`.
+- REQ-BLD-ASSEMBLER: **Assembler** (3×3): The player selects a recipe from the config-defined crafting tree. Produces what that recipe produces (REQ-MAT-OUTPUT-GROUP) at the rate defined in the corresponding `recipes.toml [[recipe]]` entry with `building = "assembler"`. Only implicitly unlocked recipes are available for selection (REQ-LOCK-UI-RECIPE).
+- REQ-BLD-REPROCESSING: **Reprocessing Plant** (3×3): Consumes scrap and returns a higher-tier material chosen by chance, as the value-preserving counterpart to smelting scrap down (REQ-BLD-SMELTER) and the only source of voidsteel. Its inputs, output groups and weights are ordinary recipe config (REQ-MAT-OUTPUT-GROUP) with `building = "reprocessing_plant"`; nothing about its behaviour is specific to the building. Reprocessing recipes take no part in the implicit unlock traversal (REQ-LOCK-IMPLICIT), so what it can yield is governed by REQ-LOCK-OUTPUT-POOL alone.
+- REQ-BLD-AUTO-RECIPE: **Automatic recipe selection.** The Smelter and the Reprocessing Plant (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING) are *auto-recipe buildings*. They carry a selected recipe and are configured exactly as a Miner or Assembler is — the same selection button and dialog (REQ-UI-SELECT-BUTTON), buffers sized for that one recipe alone (REQ-MAT-INPUT-BUFFER, REQ-MAT-OUTPUT-BUFFER), and the same pre-configuration on a construction site (REQ-BLD-SITE-CONFIG). They differ in one respect only:
+  - **Selection while none is set.** When such a building has no recipe, the first material offered at any of its input ports that some recipe of its type consumes selects that recipe; the material is then accepted as normal. This holds for every intake path — a belt, splitter or tunnel exit at an input port, and a directly coupled producer (REQ-MAT-DIRECT-COUPLE) — because a building that accepts nothing would otherwise leave a coupled producer stuck at its port forever. The choice is deterministic: input ports are examined in order, and where several recipes of the type consume the offered material the first in config order wins.
+  - **No further switching.** Once a recipe is set the building keeps it. It does not switch when its buffers run empty, nor when a material belonging to another of its recipes arrives — that material is simply not an accepted input, exactly as for any other building.
+  - **The player is always in control.** Selecting a different recipe clears the buffers (REQ-MAT-INPUT-BUFFER, REQ-MAT-OUTPUT-BUFFER); that is how a building left holding part of a cycle nothing feeds any more is freed, and how a selection the player did not want is corrected. For these buildings the dialog's clearing option is captioned `(Auto)` rather than `(None)` (REQ-UI-SELECT-OPTIONS): it unsets the recipe and hands the building back to automatic selection.
 - REQ-BLD-SHIPYARD: **Shipyard** (4×2): The player selects a schematic. When all required materials — the ship's base materials (`[ship.schematic].materials`) plus the materials of all modules in the configured layout (REQ-MOD-MATERIALS) — are present in its input buffer, the shipyard consumes them and begins a production cycle lasting the ship's base `[ship.schematic].production_time_seconds` plus the sum of production times contributed by all module instances in the configured layout (REQ-MOD-PRODUCTION-TIME). One ship of that type is spawned with the configured modules when the cycle completes. The shipyard cannot start a new cycle while one is in progress. If the player confirms a layout change (REQ-MOD-UI-DIALOG) while a production cycle is in progress, the current cycle is cancelled and all consumed materials are discarded; the shipyard returns to idle with the new layout configuration. Confirming a layout identical to the one already configured is not a change and cancels nothing (REQ-MAT-INPUT-BUFFER).
-- REQ-BLD-SALVAGE-BAY: **Salvage Bay** (3×2): A dedicated drop-off point for salvage ships. It has an output buffer whose holding capacity is defined by the `output_buffer_capacity` field of the `salvage_bay` entry in `buildings.toml` (rather than by a production cycle, since the Salvage Bay has no recipe). A ship at the bay hands over one unit of scrap per tick while the buffer has free space; a full buffer blocks further drop-off until space frees up (consistent with the buffer-full semantics of REQ-MAT-OUTPUT-BUFFER). Held scrap is pushed onto connected output belts.
+- REQ-BLD-SALVAGE-BAY: **Salvage Bay** (3×2): A dedicated drop-off point for salvage ships. It has a single output buffer — scrap is the only thing it ever holds — whose holding capacity is defined by the `output_buffer_capacity` field of the `salvage_bay` entry in `buildings.toml` (rather than by a production cycle, since the Salvage Bay has no recipe). A ship at the bay hands over one unit of scrap per tick while the buffer has free space; a full buffer blocks further drop-off until space frees up (consistent with the buffer-full semantics of REQ-MAT-OUTPUT-BUFFER). Held scrap is pushed onto connected output belts.
 - REQ-BLD-BELT: **Belt** (1×1): Transports items. A belt tile has one direction (N, S, E, W) set at placement (modified by rotation). Curved belts are auto-derived: when a belt tile's outgoing direction leads into another belt whose direction is orthogonal, the downstream belt is rendered and behaves as a curve. Belt speed is defined in `world.toml [world].belt_speed_tiles_per_second` (REQ-GW-BELT-SPEED). A belt accepts items only through a non-output edge (REQ-MAT-ACCEPT-DIR).
-- REQ-BLD-SPLITTER: **Splitter** (1×1): Distributes incoming items between two output directions. Incoming items are accepted only through the splitter's non-output edges (REQ-MAT-ACCEPT-DIR). Each output can optionally have a filter (a list of item types), configurable via the selected building panel; only implicitly unlocked item types are available as filter options (REQ-LOCK-UI-SPLITTER). Routing rules:
+- REQ-BLD-SPLITTER: **Splitter** (1×1): Distributes incoming items between two output directions. Incoming items are accepted only through the splitter's non-output edges (REQ-MAT-ACCEPT-DIR). Each output can optionally have a filter (a list of item types), configurable via the selection panel; only implicitly unlocked item types are available as filter options (REQ-LOCK-UI-SPLITTER). Routing rules:
   - An item matching only one output's filter is routed to that output.
   - An item matching both outputs' filters is distributed by strict alternation between those outputs.
   - An item matching neither output's filter is routed to the unfiltered output. If both outputs have a filter and the item matches neither, the splitter stalls and moves no items until the situation is resolved.
@@ -188,8 +191,8 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
   - **Intake rendering (no pop-out).** Mirror of the emergence rendering in REQ-MAT-OUTPUT-EMERGE: the building is rendered over the input belt, so an in-transit item is occluded while inside the footprint and is only visible as it crosses the outer edge — appearing to sink into the port. The portion inside the footprint is hidden, and the item disappears at the tile centre (progress 0.5) as it enters the buffer.
 - REQ-MAT-OUTPUT-PORT: Each building has one or more fixed output port(s) defined by its surface_mask (direction determined by rotation). Produced items do not appear on the outgoing belt instantly; each item leaves the building by first emerging across the output port tile on that port's own output belt and then transferring onto the adjacent real belt tile (REQ-MAT-OUTPUT-EMERGE). The adjacent belt's direction is otherwise unconstrained (it may flow away from the building or perpendicular to it), except that a belt oriented with its own output edge facing back into the building refuses the transfer and the item stays stuck at the port (REQ-MAT-ACCEPT-DIR, REQ-MAT-OUTPUT-EMERGE).
 - REQ-MAT-OUTPUT-EMERGE: Items emerge from a building output port as an animation rather than popping directly onto the outgoing belt. Each output port has its own **output belt** — a virtual belt tile occupying the output port tile, oriented in the port's facing direction, with progress 0.0 at the tile's inner edge and 1.0 at the outer (port) edge adjacent to the next real belt tile. It reuses the belt subsystem: movement at belt speed (REQ-GW-BELT-SPEED), item rendering and spacing (REQ-GW-TILE-SIZE), and capacity/packing (REQ-GW-BELT-CAPACITY), but restricted to the 0.5→1.0 half of the tile. This applies to every building that outputs items onto belts (Miner, Smelter, Assembler, Reprocessing Plant, Salvage Bay); it does not apply to the Shipyard, which spawns a ship rather than a belt item (REQ-SHP-SPAWN-PLAYER).
-  - **Feeding.** While the output buffer (REQ-MAT-OUTPUT-BUFFER) holds an item that has not yet begun emerging and the output belt's entry slot at progress 0.5 is free (per REQ-GW-BELT-CAPACITY spacing — no emerging item within a quarter tile of progress 0.5), the next buffered item is placed on the output belt at progress 0.5. Because only the 0.5→1.0 span is used, the output belt holds at most three emerging items (progress 0.5, 0.75, 1.0); once that span is full the building places no further items on it even if the output buffer still holds more.
-  - **Cosmetic hold.** An emerging item still counts as residing in the output buffer (REQ-MAT-GLOBAL-STOCK) for the whole animation; it only leaves the building when it transfers onto a real belt tile at progress 1.0. The output belt therefore adds no inventory capacity beyond the output buffer, and clearing the output buffer on a recipe or schematic change (REQ-MAT-OUTPUT-BUFFER) also removes any items currently emerging.
+  - **Feeding.** While the output buffers (REQ-MAT-OUTPUT-BUFFER) hold an item that has not yet begun emerging and the output belt's entry slot at progress 0.5 is free (per REQ-GW-BELT-CAPACITY spacing — no emerging item within a quarter tile of progress 0.5), the longest-waiting buffered item is placed on the output belt at progress 0.5. Items leave in the order they were produced whatever their type, so per-item-type buffers do not reorder what comes out of the port. Because only the 0.5→1.0 span is used, the output belt holds at most three emerging items (progress 0.5, 0.75, 1.0); once that span is full the building places no further items on it even if the output buffers still hold more.
+  - **Cosmetic hold.** An emerging item still counts as residing in its output buffer (REQ-MAT-GLOBAL-STOCK) for the whole animation; it only leaves the building when it transfers onto a real belt tile at progress 1.0. The output belt therefore adds no inventory capacity beyond the output buffers, and clearing them on a recipe or schematic change (REQ-MAT-OUTPUT-BUFFER) also removes any items currently emerging.
   - **Travel & handoff.** An emerging item advances from progress 0.5 to 1.0 at belt speed. At progress 1.0 it attempts to transfer onto the adjacent real belt tile using the normal belt hand-off and accept-direction rules (REQ-MAT-OUTPUT-PORT, REQ-MAT-ACCEPT-DIR): the transfer succeeds only if a transport tile exists there, is not oriented with its output edge facing back into the building, and has free space. On success the item leaves the output buffer and becomes an ordinary item on that belt tile. If instead the output port tile is a directly adjacent building's input edge, the item transfers straight into that building (REQ-MAT-DIRECT-COUPLE).
   - **Stuck items.** If there is no next real belt tile and no directly-coupled building (REQ-MAT-DIRECT-COUPLE), or the transfer is refused or blocked, the emerging item stops at progress 1.0 and is rendered there (still counted in the output buffer). Following items pile up behind it at progress 0.75 and 0.5 per the packing above, and once the 0.5→1.0 span is full no further items emerge until the front item transfers.
   - **Emergence rendering (no pop-in).** An emerging item must not simply appear at progress 0.5. The output port tile's building is rendered over the output belt, so an emerging item is occluded while inside the footprint and is revealed progressively as it slides past the port edge — appearing to physically emerge from the building. The portion of the item still within the output port tile is hidden; the portion past the outer edge is drawn.
@@ -199,9 +202,13 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 - REQ-MAT-ACCEPT-DIR: A transport tile (belt, splitter, tunnel entry, or tunnel exit) accepts an incoming item only through a non-output edge; an item that would enter through one of the tile's output edges is refused. For a belt or a tunnel entry/exit the sole output edge is the one in its facing direction; for a splitter either of its two output directions is an output edge. This applies both to items pushed from an adjacent transport tile and to items deposited by a building's output port (REQ-MAT-OUTPUT-PORT).
 - REQ-MAT-INPUT-BUFFER: Each building has one input buffer per required input material. Each per-material buffer holds up to twice that material's per-cycle requirement. When the player selects a new recipe or schematic, all items in all input buffers are cleared.
   - **Setting a configuration to the value it already holds is a no-op.** Selecting the recipe or schematic already set, or applying a ship layout identical to the one already configured, changes nothing: buffers are not cleared, an in-progress production cycle is not cancelled (REQ-BLD-SHIPYARD), and a construction site's progress and stored settings are untouched. This holds however the setting is applied — through the selection dialog (REQ-UI-SELECT-BUTTON), the layout configuration dialog (REQ-MOD-UI-DIALOG), a blueprint placement (REQ-UI-BLUEPRINT-PLACE), or a blueprint configuration transfer (REQ-UI-BLUEPRINT-TRANSFER). Only a setting that genuinely differs has effects.
-- REQ-MAT-OUTPUT-BUFFER: Each building has an output buffer that holds up to twice the quantity produced by one production cycle. If the output buffer is full, production stops until space is available. When the player selects a new recipe or schematic, all items in the output buffer are cleared (relevant when the adjacent belt is jammed and items have accumulated). Re-applying a setting the building already has clears nothing, per REQ-MAT-INPUT-BUFFER.
-- REQ-MAT-OUTPUT-BUFFER-REPROCESSING: Exception to REQ-MAT-OUTPUT-BUFFER — the Reprocessing Plant's output buffer holds at most one cycle's output. This prevents exploits where the player stalls the output belt to force the plant to reroll.
-- REQ-MAT-CYCLE: Production cycle lifecycle. When a building is idle, it attempts to start a new cycle: (a) all required inputs must be present in the per-material input buffers, and (b) the cycle's output must fit in the output buffer. For the Reprocessing Plant, the output is picked at cycle start (weighted pick); the cycle only starts if that chosen output fits. On cycle start, inputs are consumed immediately and the production timer begins. On cycle completion, the (already-decided) output is deposited into the output buffer and the building returns to idle.
+- REQ-MAT-OUTPUT-GROUP: **What a recipe produces.** A recipe's output is defined as one or more **output groups**, each carrying a probability weight and a list of item/amount pairs. One cycle produces the items of exactly **one** group, decided at cycle start (REQ-MAT-CYCLE); the items within that group are all produced together.
+  - A recipe with a **single group** always produces it. There is nothing to choose, so no weight is consulted, no randomness is involved, and no eligibility is tested (REQ-LOCK-OUTPUT-POOL). This is the ordinary recipe, and the shape of all but the reprocessing ones.
+  - A recipe with **several groups** picks one by weight at cycle start. Weights are normalized at load time; their sum does not need to equal 1.
+  - There is no separate deterministic and probabilistic kind of recipe: the two are one shape with one group and with several. Every rule about outputs is written over groups, so none of them needs to distinguish the two cases — or which building runs the recipe.
+  - **Config shape.** A group is a `[[recipe.output_group]]` entry with `probability` and `items = [{item, amount}, ...]`. The single-group case may instead be written as `outputs = [{item, amount}, ...]`, which means exactly one group holding those items. A recipe uses one form or the other; both present fails config load.
+- REQ-MAT-OUTPUT-BUFFER: Each building has **one output buffer per item its recipe can produce** — every item of every one of its output groups (REQ-MAT-OUTPUT-GROUP). Each per-material buffer holds up to twice that item's per-cycle amount, meaning the largest total any single group produces of it, mirroring the input side (REQ-MAT-INPUT-BUFFER); a buffer's contents never occupy another item's capacity. An emerging item still occupies its buffer for the whole animation (REQ-MAT-OUTPUT-EMERGE). Whether a buffer without room stops production is decided by REQ-MAT-CYCLE. When the player selects a new recipe or schematic, all items in all output buffers are cleared (relevant when the adjacent belt is jammed and items have accumulated). Re-applying a setting the building already has clears nothing, per REQ-MAT-INPUT-BUFFER. Two buildings stand outside this rule: the Shipyard has no output buffer at all, since it spawns a ship rather than producing items (REQ-BLD-SHIPYARD), and the Salvage Bay has no recipe, so its single scrap buffer is sized by config instead (REQ-BLD-SALVAGE-BAY).
+- REQ-MAT-CYCLE: Production cycle lifecycle. When a building is idle, it attempts to start a new cycle: (a) all required inputs must be present in the per-material input buffers, and (b) **every one** of the recipe's output groups must fit — for each group, the items it would produce must fit in their own output buffers (REQ-MAT-OUTPUT-GROUP, REQ-MAT-OUTPUT-BUFFER). With a single group (b) is simply that group. With several it means every possible outcome, tested **before** one is picked: the pick is committed the moment the cycle begins, and a cycle whose result could not be stored must not be started at all. Testing every outcome rather than the picked one is what keeps a stalled output belt from biasing the distribution — with one item type's buffer full the building stops entirely instead of going on producing only the others. On cycle start the group is picked (by weight where there is more than one, REQ-MAT-OUTPUT-GROUP), inputs are consumed immediately, and the production timer begins. On cycle completion the (already-decided) items are deposited into their output buffers and the building returns to idle.
 - REQ-MAT-GLOBAL-STOCK: The building blocks stock is the only global inventory. All other materials exist only in building buffers or on belt tiles.
 
 ## Resources
@@ -266,9 +273,9 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 
 ### Module Placement
 
-- REQ-MOD-PLACEMENT: In the layout configuration dialog (REQ-MOD-UI-DIALOG), the player places modules onto the ship's layout grid. Clicking a module button in the module selection grid enters module placement mode for that module type. While in placement mode, a ghost of the module's surface mask is rendered at the cell under the cursor. Clicking a valid position places one instance of the module. A position is valid if every `O` cell in the module's (rotated) surface mask coincides with an unoccupied buildable cell of the ship's layout. The player may place unlimited instances of the same module type.
+- REQ-MOD-PLACEMENT: In the layout configuration dialog (REQ-MOD-UI-DIALOG), the player places modules onto the ship's layout grid. Clicking a module button in the module selection grid enters module placement mode for that module type. While in placement mode, a ghost of the module's surface mask is rendered at the cell under the cursor. Clicking a valid position places one instance of the module. A position is valid if every `O` cell in the module's (rotated) surface mask coincides with an unoccupied buildable cell of the ship's layout. The player may place unlimited instances of the same module type. Placement mode is left by pressing Q, which clears the selected module before it reaches the dialog itself (REQ-UI-DIALOG-DISMISS), and by the existing gestures: clicking the same module button again, picking another module, or entering remove mode (REQ-MOD-REMOVE).
 - REQ-MOD-ROTATION: While in module placement mode, pressing R rotates the module ghost 90° counter-clockwise and Shift+R rotates it 90° clockwise. Rotation transforms the surface mask grid identically to building rotation (REQ-BLD-ROTATE).
-- REQ-MOD-REMOVE: The module selection grid includes a "Remove" button. Clicking it enters remove mode. In remove mode, clicking on a cell occupied by a placed module removes that entire module instance from the layout. Remove mode is exited by clicking the Remove button again or by selecting a module for placement.
+- REQ-MOD-REMOVE: The module selection grid includes a "Remove" button. Clicking it enters remove mode. In remove mode, clicking on a cell occupied by a placed module removes that entire module instance from the layout. Remove mode is exited by clicking the Remove button again, by selecting a module for placement, or by pressing Q, which leaves the mode before it reaches the dialog itself (REQ-UI-DIALOG-DISMISS).
 
 ### Module Effects
 
@@ -283,7 +290,7 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
   - **Miner recipe**: `duration_seconds / output_amount`, where `output_amount` is the number of units produced per cycle.
   - **Smelter recipe**: `(duration_seconds + Σ (input_threat × input_amount)) / output_amount`, where the sum is over all inputs.
   - **Assembler recipe**: `(duration_seconds + Σ (input_threat × input_amount)) / output_amount`, where the sum is over all inputs.
-  - **Reprocessing-only item** (an item type that has no miner, smelter, or assembler recipe producing it, and is only obtainable via reprocessing): `(scrap_threat × scrap_per_cycle + duration_seconds) / probability`, where `scrap_threat` is the threat value of scrap (see REQ-THREAT-SCRAP), `scrap_per_cycle` is the number of scrap consumed per reprocessing cycle, `duration_seconds` is the reprocessing cycle time, and `probability` is the normalized weight of that item in the reprocessing output pool. (Reprocessing output amounts are 1 in practice, so per-unit division is already implicit in the formula.)
+  - **Item from a recipe that picks between output groups** (an item type produced by no single-group recipe, and so obtainable only where a cycle picks one outcome of several — REQ-MAT-OUTPUT-GROUP): `(scrap_threat × scrap_per_cycle + duration_seconds) / probability / output_amount`, where `scrap_threat` is the threat value of scrap (see REQ-THREAT-SCRAP), `scrap_per_cycle` is the scrap consumed per cycle, `duration_seconds` is the cycle time, `probability` is the group's normalized weight, and `output_amount` is how many units of the item that group yields. The cycle's cost is divided by the odds of getting the group at all, and then by how many units it yields, so the value is per unit as everywhere else in this requirement.
   - **Multiple recipes**: if an item type can be produced by more than one non-reprocessing recipe (miner, smelter, or assembler), its threat value is the **maximum** across **all** such eligible recipes, and the threat is committed only once every eligible recipe is computable (so a shallow shortcut recipe that resolves earlier than a deeper base recipe cannot lower the item's threat). The reprocessing path is only used when no other recipe exists. If recipe cycles prevent full resolution, the max over the currently computable subset is used as a fallback.
   - **Scrap-consuming recipe fallback**: a non-reprocessing recipe that takes `scrap` as an input participates in an item's threat computation only if no scrap-free recipe (miner, smelter, or assembler) produces that item. This mirrors the reprocessing fallback rule and prevents the scrap-to-ingot smelter recipe from inflating basic material threats via the max rule.
 
@@ -306,19 +313,19 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 
 ### Module UI
 
-- REQ-MOD-UI-PREVIEW: For a selected shipyard (operational building or construction site), the selected building panel always shows a small non-interactive **ship layout preview** widget below the schematic selection button (REQ-UI-SELECT-BUTTON) and a "Configure" button below the preview. Both are **disabled while no schematic is selected**, and enabled once one is; the preview then shows an empty placeholder in place of a layout grid. When a schematic is selected, the preview renders the ship's layout grid at a reduced scale: buildable cells without a module are shown as white, non-buildable cells are shown as black, and cells occupied by a module are shown in that module's `fill_color` with the module's `glyph` character. For non-shipyard buildings, neither the preview nor the "Configure" button is shown.
-- REQ-MOD-UI-DIALOG: Clicking the "Configure" button opens the **layout configuration dialog** as a modal. While the dialog is open, the game is paused (speed set to 0×). On close, the game speed is restored to what it was before the dialog was opened.
+- REQ-MOD-UI-PREVIEW: For a selected shipyard (operational building or construction site), the selection panel always shows a small non-interactive **ship layout preview** widget below the schematic selection button (REQ-UI-SELECT-BUTTON) and a "Configure" button below the preview. Both are **disabled while no schematic is selected**, and enabled once one is; the preview then shows an empty placeholder in place of a layout grid. When a schematic is selected, the preview renders the ship's layout grid at a reduced scale: buildable cells without a module are shown as white, non-buildable cells are shown as black, and cells occupied by a module are shown in that module's `fill_color` alone — no glyph, which at this scale would not be legible anyway; the layout configuration dialog's full-scale grid is where a module is identified by its glyph (REQ-MOD-UI-DIALOG). For non-shipyard buildings, neither the preview nor the "Configure" button is shown.
+- REQ-MOD-UI-DIALOG: Clicking the "Configure" button opens the **layout configuration dialog** as a modal, centered on the selection panel it was opened from (REQ-UI-PANEL-MODAL). While the dialog is open, the game is paused (speed set to 0×). On close, the game speed is restored to what it was before the dialog was opened.
 
   The dialog contains:
   - **Top**: The ship's layout grid rendered at full scale. Buildable cells are white; non-buildable cells are black. Placed modules are rendered with their `fill_color` and `glyph`. The ghost of the currently selected module is shown at the cursor position when in placement mode.
-  - **Left** (below the grid): The ship stats panel (see REQ-MOD-UI-STATS-PANEL).
-  - **Center** (below the grid): A grid of module selection buttons (one per **unlocked** module type; see REQ-DEF-SCHEMATIC-DROP) plus a "Remove" button. Each module button shows the module id and its glyph.
+  - **Left** (below the grid): The ship stats panel (see REQ-MOD-UI-STATS-PANEL), and beneath it the layout's **build cost**, so the price of a configuration is visible while it is being assembled rather than only once it has been confirmed: the total materials required for the ship — the union of the schematic's base materials and those of every placed module, summed per item type (REQ-MOD-MATERIALS) — drawn as item icons on their colored squares with their amounts (REQ-UI-ITEM-ICON), and beside them the total production time (REQ-MOD-PRODUCTION-TIME). Both update in real time as modules are placed and removed. The cost sits beside the stats panel rather than within it because a build cost belongs to a ship being configured: the same panel serves an existing ship (REQ-UI-SHIP-STATS-PANEL) and the balancing tool, neither of which costs anything.
+  - **Center** (below the grid): A grid of module selection buttons (one per **unlocked** module type; see REQ-DEF-SCHEMATIC-DROP) plus a "Remove" button. A module button shows the module's name — its `id` under the usual display convention — on its first line, and beneath it what the module costs: the icons of its `materials` items on their colored squares with their amounts (REQ-UI-ITEM-ICON) and the production time it adds, as `+<n> s` (REQ-MOD-MATERIALS, REQ-MOD-PRODUCTION-TIME). This is the same form a recipe option button uses to state what it makes (REQ-UI-SELECT-OPTIONS), and it puts the price of a module in front of the player before it is placed. The "Remove" button costs nothing and shows its caption alone.
   - **Right** (below the grid): The layout blueprint panel (see REQ-MOD-UI-BLUEPRINT-PANEL through REQ-MOD-UI-BLUEPRINT-FILE-LOAD).
-  - **Bottom**: A "Confirm" button and a "Cancel" button. Cancel discards all changes made in this dialog session and closes the dialog. Confirm applies the changes: the shipyard's configured layout is updated, the required materials and cycle time displayed in the selected building panel are recalculated, and the ship layout preview is refreshed.
+  - **Bottom**: A "Confirm" button and a "Cancel" button. Cancel discards all changes made in this dialog session and closes the dialog; Q is a second way to reach it, once nothing is left to back out of within the dialog (REQ-UI-DIALOG-DISMISS). Confirm applies the changes: the shipyard's configured layout is updated, the required materials and cycle time displayed in the selection panel are recalculated, and the ship layout preview is refreshed.
 
 - REQ-MOD-UI-EMPTY-PULSE: While a module is selected for placement in the layout configuration dialog (REQ-MOD-UI-DIALOG), the empty buildable cells of the layout grid pulse smoothly around their normal fill shade, oscillating between a slightly darker and a slightly brighter shade at approximately 1 Hz (one full cycle per second), to draw the player's attention to where the module can be placed. All empty buildable cells pulse in phase. When no module is selected for placement (including remove mode), empty buildable cells render at their normal static shade. Non-buildable cells and cells occupied by a placed module do not pulse.
 
-- REQ-MOD-UI-AUTO-DIALOG: When the player selects a schematic for a shipyard (operational building or construction site) through the schematic selection dialog (REQ-UI-SELECT-BUTTON), and the chosen schematic **differs** from the shipyard's current schematic, the layout configuration dialog (REQ-MOD-UI-DIALOG) opens automatically and immediately once the selection dialog closes — exactly as if the player had then clicked "Configure". Re-selecting the schematic already set does not reopen the dialog. This auto-open applies only to the manual schematic selection dialog; a schematic applied by blueprint placement (REQ-UI-BLUEPRINT-PLACE) does **not** auto-open the dialog. The player may still cancel the auto-opened dialog (REQ-MOD-UI-DIALOG), which leaves the newly selected schematic in place with its default empty layout; the "Configure" button (REQ-MOD-UI-PREVIEW) remains available to open the dialog again later.
+- REQ-MOD-UI-AUTO-DIALOG: When the player selects a schematic for a shipyard (operational building or construction site) through the schematic selection dialog (REQ-UI-SELECT-BUTTON), and the chosen schematic **differs** from the shipyard's current schematic, the layout configuration dialog (REQ-MOD-UI-DIALOG) opens automatically and immediately once the selection dialog closes — exactly as if the player had then clicked "Configure". Re-selecting the schematic already set does not reopen the dialog. Neither does **clearing** the shipyard: the `(None)` option (REQ-UI-SELECT-OPTIONS) differs from whatever was set, but it names no schematic and leaves nothing to configure, so no dialog opens — the same condition under which the "Configure" button is disabled (REQ-MOD-UI-PREVIEW). This auto-open applies only to the manual schematic selection dialog; a schematic applied by blueprint placement (REQ-UI-BLUEPRINT-PLACE) does **not** auto-open the dialog. The player may still cancel the auto-opened dialog (REQ-MOD-UI-DIALOG), which leaves the newly selected schematic in place with its default empty layout; the "Configure" button (REQ-MOD-UI-PREVIEW) remains available to open the dialog again later.
 
 - REQ-MOD-UI-MODULE-TOOLTIP: Each module selection button in the layout configuration dialog (REQ-MOD-UI-DIALOG) shows a hover tooltip with the descriptive text defined for that module type in `modules.toml` (the optional per-module tooltip field). If a module type defines no tooltip text, its button shows no tooltip. The "Remove" button is not a module type and has no config-defined tooltip.
 
@@ -372,9 +379,11 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 
   Each option in the dialog displays the unlock group's display name — derived from its `id` (same display convention as building, module, and recipe ids) — and the list of items it would grant: its ship, module, building, and assembler-recipe ids (each shown with the same display convention as its respective selection dialog). The artifact option (if present) is displayed as a distinct entry with the name "Artifact".
 
-  Each option additionally displays a vertical list of recipe names labeled "Unlocks recipes:", showing which miner and assembler recipes would newly become implicitly unlocked (REQ-LOCK-IMPLICIT) if this option were selected — specifically, the miner recipes and implicitly-gated assembler recipes that are not currently implicitly unlocked but would become so after applying this option's effect. To compute this, all `materials` of the group's granted ship and module schematics are added to the base set per REQ-LOCK-IMPLICIT step 1a, and the output items of the group's granted assembler recipes are added per step 1b, before recomputation.
+  Each option additionally displays a vertical list of recipe lines labeled "Unlocks recipes:", showing which miner and assembler recipes would newly become implicitly unlocked (REQ-LOCK-IMPLICIT) if this option were selected — specifically, the miner recipes and implicitly-gated assembler recipes that are not currently implicitly unlocked but would become so after applying this option's effect. To compute this, all `materials` of the group's granted ship and module schematics are added to the base set per REQ-LOCK-IMPLICIT step 1a, and the output items of the group's granted assembler recipes are added per step 1b, before recomputation.
 
-  Each recipe is listed by its `id` (using the same display convention as the assembler recipe-selection dialog), sorted alphabetically. Hovering a recipe in this list displays the recipe info tooltip described for a recipe in REQ-UI-SELECT-TOOLTIP (the recipe name; the name and quantity of each input item; the completion time; and the name and quantity of the produced output item). If no recipes would be newly unlocked, the list shows "None".
+  Each recipe is shown as a **recipe line** of the same two-row card the item production tooltip uses (REQ-UI-ITEM-TOOLTIP): the icon of the building that runs it (REQ-UI-BUILD-ICON) and the recipe's name — by its `id`, using the same display convention as the assembler recipe-selection dialog — on the first row, and the recipe drawn as the recipe summary draws it (REQ-UI-RECIPE-SUMMARY) on the second. The lines are sorted alphabetically by recipe name. The line says everything there is to say about the recipe, so nothing in this list carries a tooltip, as in the selection dialog (REQ-UI-SELECT-OPTIONS). If no recipes would be newly unlocked, the list shows "None".
+
+  **The dialog cannot be dismissed.** Clicking an option is the only thing that closes it: it has no close button, no Cancel, and neither Escape nor Q dismisses it (REQ-UI-DIALOG-DISMISS). The drop is a reward the player has earned by destroying the station set, and every way out of the dialog would have to either forfeit it or pick an option the player did not — so there is no way out but choosing. The dialog is modal and the game is paused meanwhile, so nothing is waiting on the decision.
 
   The player selects one option by clicking it. If the player selects the artifact option, the player's artifact count is incremented by 1 (REQ-WIN-ARTIFACT-COUNT) and the dialog closes; no unlock is applied. Otherwise the selected unlock group is awarded and the dialog closes: every ship, module, building, and assembler recipe the group grants becomes unlocked at once — ship schematics unlock the corresponding shipyard selection; module schematics unlock the module type for placement in the layout configuration dialog (REQ-MOD-UI-DIALOG); building types become available in the build menu (REQ-LOCK-BUILDING); assembler recipes become available in the assembler recipe-selection dialog (subject to REQ-LOCK-UI-RECIPE). The unlock group is removed from the pool permanently (REQ-LOCK-EXPLICIT), and the implicit unlock set is recomputed (REQ-LOCK-IMPLICIT).
 
@@ -385,14 +394,16 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 - REQ-LOCK-PREREQ: An unlock group may optionally define `requires` — a list of prerequisite **unlock-group ids** that must already have been awarded before this group may enter the drop pool. A prerequisite is **satisfied** only when the unlock group it names has been awarded (REQ-LOCK-EXPLICIT). This check is applied in addition to the conditions in REQ-DEF-SCHEMATIC-DROP: a group enters the eligible pool only when its `station_level` condition is met, it has not yet been awarded, and every id in its `requires` is satisfied. `requires` defaults to empty (no prerequisites). The check is re-evaluated against the current set of awarded unlock groups every time a drop pool is built (after each REQ-DEF-SCHEMATIC-DROP and on Restart per REQ-CFG-RELOAD), so a gated group becomes eligible in the first drop after its last prerequisite is awarded. Every id listed in any `requires` must resolve to an unlock group defined in `unlocks.toml`; an id that names no such group is a configuration error that fails config load with a descriptive message (config is loaded at startup and reloaded on Restart, REQ-CFG-RELOAD). An unlock group that lists itself, or a cycle of mutually dependent prerequisites, is not a load error but can never become eligible, since no group in the cycle can be the first to be awarded.
 
 - REQ-LOCK-IMPLICIT: Item types and miner/assembler recipes are **implicitly** unlocked or locked based on the current set of unlocked ship, module, and assembler recipe schematics. The implicit unlock set is recomputed whenever any schematic changes lock state (on Restart or after REQ-DEF-SCHEMATIC-DROP). Computation:
-  1. Start with the union of: (a) all item types listed in `materials` across all currently unlocked ship schematics and all currently unlocked module schematics, and (b) the output item type of every assembler recipe that is currently **explicitly available** — that is, either flagged `unlocked_at_start` in `recipes.toml`, or granted by an unlock group that has been awarded (REQ-LOCK-EXPLICIT).
+  1. Start with the union of: (a) all item types listed in `materials` across all currently unlocked ship schematics and all currently unlocked module schematics, and (b) the output item types of every assembler recipe that is currently **explicitly available** — that is, either flagged `unlocked_at_start` in `recipes.toml`, or granted by an unlock group that has been awarded (REQ-LOCK-EXPLICIT).
   2. For each item type in the current set: for every recipe (miner, smelter, or assembler) that produces it — skipping any assembler recipe that is granted by an unlock group whose group has not yet been awarded — add each of that recipe's input item types to the set. If the recipe is a miner recipe, or an assembler recipe that is not granted by any unlock group, mark it as implicitly unlocked. Assembler recipes that are explicitly available (flagged `unlocked_at_start`, or granted by an awarded unlock group) are available in the assembler recipe-selection dialog by virtue of REQ-LOCK-EXPLICIT; their inputs are also added to the implicit set in this step.
   3. Repeat step 2 until no new item types are added.
-  Item types and miner/assembler recipes not reached by this process (and not explicitly unlocked) are locked. Smelter recipes participate in the traversal to propagate unlocking to their inputs but are never themselves shown in any UI dropdown.
+  Item types and miner/assembler recipes not reached by this process (and not explicitly unlocked) are locked. Smelter recipes participate in the traversal to propagate unlocking to their inputs but are never themselves gated by it: they are not granted by unlock groups either (REQ-LOCK-EXPLICIT), so a Smelter's dialog offers all of them once the building is unlocked (REQ-LOCK-UI-RECIPE, REQ-BLD-AUTO-RECIPE).
 
-- REQ-LOCK-REPROCESSING-POOL: The pool of possible outputs for a Reprocessing Plant cycle (REQ-BLD-REPROCESSING) is restricted to item types that are currently implicitly unlocked (REQ-LOCK-IMPLICIT). Weights are renormalized over the eligible outputs. If no eligible outputs remain, the Reprocessing Plant cannot start a production cycle.
+- REQ-LOCK-OUTPUT-POOL: **The choice between output groups is restricted to what the player can use.** Where a recipe has several output groups (REQ-MAT-OUTPUT-GROUP), only groups whose items are **all** currently implicitly unlocked (REQ-LOCK-IMPLICIT) are eligible; a group holding any locked item is dropped whole, since its items are produced together and taking it would hand the player a locked one. Weights are renormalized over the eligible groups, and if none remains the cycle cannot start.
 
-- REQ-LOCK-UI-RECIPE: Locked miner ore-type recipes and assembler recipes are not shown in their respective recipe-selection dialogs (REQ-UI-SELECT-BUTTON).
+  The restriction is on the **choice**, not on production: a recipe with a single group has no choice to restrict and is never tested for eligibility. This distinction is load-bearing rather than an optimization. Implicit unlocking is derived from demand — an item becomes unlocked because something the player can build needs it (REQ-LOCK-IMPLICIT) — so an ordinary recipe's output can be perfectly producible while nothing yet calls for it. Testing eligibility there would not gate a drop, it would stop the building producing at all. In practice this governs the Reprocessing Plant, the only building whose recipes have several groups (REQ-BLD-REPROCESSING).
+
+- REQ-LOCK-UI-RECIPE: Locked miner ore-type recipes and assembler recipes are not shown in their respective recipe-selection dialogs (REQ-UI-SELECT-BUTTON). Smelter and Reprocessing Plant recipes are never granted by an unlock group (REQ-LOCK-EXPLICIT restricts `recipes` grants to assembler recipes), so they are available from the start and their dialogs list them all; what gates them in practice is whether the building itself is unlocked (REQ-LOCK-BUILDING).
 
 - REQ-LOCK-UI-SCHEMATIC: Locked ship schematics are not shown in the shipyard's schematic-selection dialog (REQ-UI-SELECT-BUTTON).
 
@@ -428,24 +439,25 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 
 ### Layout
 
-The screen is divided into two columns: a main column (75% width) containing the header bar and game world, and a side panel column (25% width) holding the selected building panel. The build button bar (REQ-UI-BUILD-BAR) is not part of either column — it floats over the game world at its bottom center. Blueprints have no permanent screen real estate; they are reached through modal dialogs (REQ-UI-BLUEPRINT-DIALOG):
+The screen is a single column: a header bar across the top and the game world view filling the whole area below it. There is no side panel. All three permanent UI widgets float over the game world — the build button bar (REQ-UI-BUILD-BAR) at its bottom center, the selection panel (REQ-UI-SELECTION-PANEL) beside whatever is currently selected — or wherever the player has dragged it by its header (REQ-UI-SELECTION-PANEL-DRAG) — shown only while something is selected and holding its place on the screen until the next selection, and the controls panel (REQ-UI-CONTROLS-PANEL) in its bottom-left corner, beside the build button bar and rising above it only when the two would overlap. Blueprints have no permanent screen real estate; they are reached through modal dialogs (REQ-UI-BLUEPRINT-DIALOG):
 
 ```
-+--------------------------------------+--------------+
-|             Header Bar               |              |
-+--------------------------------------+  Selected    |
-|                                      |  Building    |
-|                                      |  Panel       |
-|           Game World                 |              |
-|                                      |              |
-|                                      |              |
-|        +------------------+          |              |
-|        | Build Button Bar |          |              |
-+--------+------------------+----------+--------------+
-           (75% width)                   (25% width)
++-----------------------------------------------------------+
+|                        Header Bar                         |
++-----------------------------------------------------------+
+|                                             +-----------+ |
+|                                             | Selection | |
+|                    Game World               |   Panel   | |
+|                                             +-----------+ |
+|                                                           |
+| +----------+                                              |
+| | Controls |     +------------------+                     |
+| |  Panel   |     | Build Button Bar |                     |
++-+----------+-----+------------------+---------------------+
+                     (full window width)
 ```
 
-- REQ-UI-HEADER: The header bar spans the width of the game world column (75% of the screen width) and always shows the elapsed survival time, the current global building blocks stock, and the artifact count (REQ-WIN-ARTIFACT-COUNT) displayed as `Artifacts: x/y` (where `x` is the current artifact count and `y` is `world.toml [world].artifact_win_count`) on the left, the boss wave counter and boss countdown (REQ-UI-BOSS-STATUS) and an asteroid expansion button (REQ-UI-EXPAND-BUTTON) to the left of the speed buttons, and game speed controls on the right.
+- REQ-UI-HEADER: The header bar spans the full width of the game window and always shows the elapsed survival time, the current global building blocks stock, and the artifact count (REQ-WIN-ARTIFACT-COUNT) displayed as `Artifacts: x/y` (where `x` is the current artifact count and `y` is `world.toml [world].artifact_win_count`) on the left, the boss wave counter and boss countdown (REQ-UI-BOSS-STATUS) and an asteroid expansion button (REQ-UI-EXPAND-BUTTON) to the left of the speed buttons, and game speed controls on the right.
 - REQ-UI-BLOCKS-ICON: In the header bar (REQ-UI-HEADER), the global building blocks stock is displayed as `Stock: <n>` followed by the `building_block` item icon (REQ-UI-ITEM-ICON) — e.g. `Stock: 200` then a small block icon — replacing the `Building Blocks: <n>` text label. The icon is sized to the header text height. When no icon file exists for `building_block` (a missing icon is not an error, REQ-UI-ITEM-ICON), the display falls back to the `Stock: <n> Blocks` text. The hover tooltip (REQ-UI-BLOCKS-TOOLTIP) applies in either form.
 - REQ-UI-BLOCKS-TOOLTIP: The header bar's building blocks stock display (REQ-UI-HEADER) shows a hover tooltip with the descriptive text defined in `world.toml [world].building_blocks_tooltip` — intended to tell the player what building blocks are used for and how to obtain them. If the field is unset, the stock display shows no tooltip. This tooltip is distinct from the build/module button tooltips (REQ-UI-BUILD-TOOLTIP, REQ-MOD-UI-MODULE-TOOLTIP).
 - REQ-UI-ARTIFACTS-TOOLTIP: The header bar's artifact count display (REQ-UI-HEADER) shows a hover tooltip with the descriptive text defined in `world.toml [world].artifact_tooltip` — intended to tell the player what artifacts are, how they are obtained (REQ-DEF-SCHEMATIC-DROP), and that collecting `world.toml [world].artifact_win_count` of them wins the game (REQ-WIN-ARTIFACT-COUNT). If the field is unset, the artifact count display shows no tooltip. This tooltip is distinct from the building blocks tooltip (REQ-UI-BLOCKS-TOOLTIP) and the build/module button tooltips (REQ-UI-BUILD-TOOLTIP, REQ-MOD-UI-MODULE-TOOLTIP).
@@ -454,9 +466,39 @@ The screen is divided into two columns: a main column (75% width) containing the
 - REQ-UI-PAUSE-BORDER: While the game is paused (speed 0×, whether set via the speed controls (REQ-UI-SPEED), the Space toggle (REQ-UI-HOTKEYS), or an auto-pausing modal), a vignette border is drawn around the edges of the game world view to make the paused state hard to miss. The border is black and fades in the alpha channel from fully transparent at its inner (center-facing) edge to 50% opacity at the viewport edge, over a thickness of 100 pixels (capped at half the smaller viewport dimension on very small views).
 - REQ-UI-DECONSTRUCT-BORDER: While deconstruct mode is active (REQ-UI-DECONSTRUCT-BUTTON, REQ-UI-HOTKEYS), a vignette border is drawn around the edges of the game world view to signal the mode, matching the geometry of the paused-state vignette (REQ-UI-PAUSE-BORDER): a 100-pixel thickness (capped at half the smaller viewport dimension on very small views) with the four sides meeting along mitred corner diagonals. It fades in the alpha channel from fully transparent at its inner (center-facing) edge to the deconstruct tint color at the viewport edge. The color — including its alpha, which sets the peak opacity at the viewport edge — is read from `visuals.toml [overlays].deconstruct_tint`, the same deconstruct-mode color used for the hover tint. The border is presentation-only and has no effect on the simulation. If the game is both paused and in deconstruct mode, both vignettes are drawn and compose over each other.
 - REQ-UI-EXPAND-BUTTON: The header bar shows an asteroid expansion button captioned `Expand: <x>` followed by the `building_block` item icon (REQ-UI-BLOCKS-ICON, REQ-UI-ITEM-ICON) in place of the trailing `Blocks` word, where `<x>` is the current expansion cost computed from `world.toml [expansion].cost_building_blocks_formula` at the current number of purchased expansions (REQ-EXP-COST). When no icon file exists for `building_block`, the caption falls back to the `Expand: <x> Blocks` text. Clicking the button unlocks the next asteroid expansion (REQ-EXP-UNLOCK, REQ-GW-ASTEROID-EXPAND), spending that many building blocks from the global stock. The button is disabled when the player cannot currently afford the cost (consistent with REQ-UI-BUILD-DISABLED). The caption updates as the cost changes with each purchased expansion.
-- REQ-UI-WORLD-SIZE: The game world view occupies the full height below the header bar in the main column (75% of the screen width).
-- REQ-UI-PANEL-COLUMN: The side panel column occupies 25% of the screen width and the full screen height. It holds a single panel filling that full height: the selected building panel. The build buttons are not part of this column; they float over the game world (REQ-UI-BUILD-BAR). Blueprints are not part of this column either; they are reached through the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG).
-- REQ-UI-MODAL-DIM: While a modal dialog, menu, or full-screen state screen is open on top of the game, a transparent black overlay (a dim/scrim) is drawn over the **entire game window** — the header bar, the game world view, and the side panel column — behind that modal, so the game reads as inactive while the modal holds focus. The overlay is shown for every modal that auto-pauses the simulation — the escape menu (REQ-UI-GAME-MENU), the recipe/schematic selection dialog (REQ-UI-SELECT-BUTTON), the layout configuration dialog (REQ-MOD-UI-DIALOG), the schematic choice dialog (REQ-DEF-SCHEMATIC-DROP), the blueprint save dialog (REQ-UI-BLUEPRINT-CREATE), and the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG) — as well as the game-over screen (REQ-HQ-GAME-OVER) and the win screen (REQ-WIN-SCREEN), which end rather than pause the game. When modals are nested (for example the Create Blueprint name dialog (REQ-MOD-UI-BLUEPRINT-CREATE) opened from the layout configuration dialog), only a single dim is shown over the game window; nested modals do not stack additional overlays. The same applies when one modal hands directly off to another — the blueprint save dialog opening the blueprint selection dialog on confirm (REQ-UI-BLUEPRINT-CREATE): the dim persists across the handoff rather than flickering off and back on, and the simulation is not resumed in between. The dim color and opacity are read from `visuals.toml [overlays]` (a semi-transparent black modal-dim color), consistent with the other overlay colors. The overlay is presentation-only and has no effect on the simulation.
+- REQ-UI-WORLD-SIZE: The game world view occupies the full width of the game window and the full height below the header bar. No widget insets it: the build button bar (REQ-UI-BUILD-BAR), the selection panel (REQ-UI-SELECTION-PANEL), and the controls panel (REQ-UI-CONTROLS-PANEL) float over it.
+- REQ-UI-SELECTION-PANEL: The **selection panel** (the panel described under Selection Panel, REQ-UI-SINGLE-SELECTION and following) is a widget that **floats over the game world view** (REQ-UI-WORLD-SIZE), placed **beside the objects it describes** rather than at a fixed corner of the view, so it appears where the player is already looking. It is **sized to its content in both width and height**, so it grows and shrinks as the content changes. Two distances shape its placement, and they are deliberately different: a small **edge margin** it keeps from the view's edges and from the widgets it steps around, and a larger **selection gap** of half a tile (REQ-GW-TILE-SIZE) it keeps from the selection itself, so the panel stands clear of the objects it describes instead of touching them. The selection gap applies **horizontally only**, on the side facing the selection; vertically the panel stays level with the selection (see **Vertical placement**).
+  - **Anchor rectangle.** The panel is placed against the screen rectangle of the selection **at the moment that selection started**: the footprint of the single object selected (a building or construction site, an actor, or a piece of debris), or, when the selection started as a multi-selection (REQ-UI-MULTI-SELECT), the bounding box of all the objects it started with.
+  - **Side.** The panel goes to the **right** of the anchor rectangle, separated from it by the selection gap, whenever it fits within the view there. Otherwise it goes to the **left** of the anchor rectangle by that same gap. The room a side offers is measured accordingly: from the anchor rectangle's edge to the view's edge, less the selection gap and less the edge margin. When it fits on neither side — a bounding box spanning most of the view, or an object too close to an edge — it is placed on whichever side leaves more room and then pushed inside the view. That is the one case in which the panel covers part of the selection.
+  - **Vertical placement.** The panel's **top edge is aligned with the anchor rectangle's top edge** and it extends downward. The selection gap plays no part here: the panel's top sits level with the top of the topmost object it describes, the gap separating the two horizontally alone. Its bottom is limited by the lowest of: the view's bottom edge less the edge margin; and the top edge, less that same margin, of the build button bar (REQ-UI-BUILD-BAR) or the controls panel (REQ-UI-CONTROLS-PANEL) — but each of those two only where the panel's own horizontal extent actually overlaps that widget's current rectangle, so a panel whose column misses them is not shortened by them. Should the panel not fit above that limit, it is shifted up, as far as the edge margin at the view's top and no further; if it still does not fit, its height is capped at the space available there and the content scrolls vertically within it.
+  - **Fixed for the life of the selection.** The anchor rectangle, the selection gap, and the side are determined once, when the selection starts, and are not revisited while that selection lasts; the panel's own size is the only thing that may still move it (see **Resizing in place** below). The gap is therefore half a tile as the tile stood in that moment, and a view resize that changes the tile size (REQ-GW-TILE-SIZE) does not change it: the anchor rectangle it is measured from is a screen rectangle frozen in the same moment, and re-measuring one against a later tile size than the other has no meaning. The player may override the resulting position by dragging the panel's header (REQ-UI-SELECTION-PANEL-DRAG); the dragged position then takes the anchor rectangle's and the side's place for the rest of that selection. The panel **keeps its place on the screen** when the player scrolls the view (REQ-UI-SCROLL) and when a selected object moves under it (a selected ship flying away), rather than following the object — which may leave it beside nothing, or beside an object that has left the view entirely. It likewise does not move when the selection is **expanded** by adding objects or reduced by removing them (REQ-UI-MULTI-SELECT), nor when a selected object is destroyed or deconstructed. Starting a **new** selection — clicking a different object, or a box drag that replaces the selection — places the panel anew against the new anchor rectangle.
+  - **Resizing in place.** Only the anchor rectangle, the selection gap, and the chosen side are fixed for the life of the selection (or, once the panel has been dragged, the dragged desired position — REQ-UI-SELECTION-PANEL-DRAG); the panel's geometry is **re-solved from them** whenever its content size changes (a section appearing or disappearing as the selection's state changes), the view is resized, or the build button bar's or controls panel's rectangle changes. Re-solving keeps the two edges the panel was placed by — its top edge, and the edge facing the anchor rectangle (its left edge when it sits to the right of the selection, its right edge when it sits to the left) — so the panel grows away from the selection rather than over it, and it never switches sides for as long as the selection lasts. What re-solving may change is the vertical result: growth that would take the panel outside the view or into either of those two widgets is resolved as in **Vertical placement** above, by shifting it up and capping its height, and a panel that shrinks again regains the room.
+  - **Visibility.** The panel is shown only while at least one object is selected. With an empty selection it is not shown at all (REQ-UI-EMPTY-SELECTION), leaving the full game world view visible.
+  - **Overlay behavior.** As for the build button bar (REQ-UI-BUILD-BAR): the panel occludes the strip of the game world it covers; the world view itself keeps its full extent and the view's scrolling, ghost rendering, and tile geometry are unaffected. It is drawn above the pause and deconstruct vignettes (REQ-UI-PAUSE-BORDER, REQ-UI-DECONSTRUCT-BORDER), which keep their full band underneath it, and below the modal dim (REQ-UI-MODAL-DIM), which covers the entire game window including the panel. The panel never overlaps the build button bar or the controls panel, because it stays above both wherever their rectangles meet its own; neither of them ever moves on the panel's account (REQ-UI-BUILD-BAR, REQ-UI-CONTROLS-PANEL).
+  - **Input.** Mouse events over the panel are consumed by the panel and never reach the game world: hovering it shows no builder-mode ghost at the tile beneath, and clicking it neither places a building nor changes the selection. Right-clicking the panel does not exit builder mode (REQ-BLD-BUILDER-MODE) or cancel a belt drag (REQ-BLD-BELT-DRAG). Beside the controls its content offers, the panel's own chrome offers one gesture: the header drag that moves it (REQ-UI-SELECTION-PANEL-DRAG).
+- REQ-UI-SELECTION-PANEL-DRAG: **Moving the panel by its header.** The player can move the selection panel by pressing the left mouse button on the panel's **header** (REQ-UI-SELECTION-CARD) and dragging: the panel follows the cursor for the duration of the drag and stays where it is dropped on release. The header is the whole drag handle, and no other part of the panel starts a drag.
+  - **Desired position, not resolved position.** A drag sets only the panel's **desired top-left corner** in view coordinates. Where the panel actually lands is resolved from that desired position by the rules of REQ-UI-SELECTION-PANEL, exactly as an anchor-derived position is: the panel keeps its edge margin from the view's edges; its bottom is limited by the top edge, less that same margin, of the build button bar (REQ-UI-BUILD-BAR) and of the controls panel (REQ-UI-CONTROLS-PANEL), but each only where the panel's own horizontal extent actually overlaps that widget's current rectangle; and a panel that does not fit above that limit is shifted up as far as the edge margin at the view's top and, failing that, capped in height with its content scrolling. The player therefore cannot park the panel over either widget, and neither widget ever moves on the panel's account (REQ-UI-BUILD-BAR, REQ-UI-CONTROLS-PANEL) — stepping around them stays entirely the panel's job.
+  - **The desired position survives the resolution.** Resolving does not overwrite what the player set: the desired position is retained as dropped, so a panel that had to be shifted up or shortened returns to it as soon as the obstruction stops overlapping it — its content shrinks, the bar's button set changes (REQ-LOCK-BUILDING), the controls panel's context changes, or the view is resized. A desired position that the current view cannot honour at all is likewise kept, so enlarging the window brings the panel back to it.
+  - **What the drag replaces.** From the first drag on, the desired position replaces the anchor rectangle and the side (REQ-UI-SELECTION-PANEL) for the rest of the current selection; the panel no longer has a side and never switches to one. The selection gap goes with the anchor rectangle it was measured from and plays no further part: a player who drags the panel onto the selection is free to put it there. Re-solving (the **Resizing in place** rule of REQ-UI-SELECTION-PANEL) then keeps the top and left edges of the desired position, in place of the top edge and the edge facing the anchor, so the panel still grows away from where the player put it rather than over it. The panel may be dragged repeatedly; each drag replaces the previous desired position.
+  - **Scope: the current selection.** The desired position lasts as long as the selection it was set in — across the panel's own resizing, view resizes, and view scrolling (REQ-UI-SELECTION-PANEL), and across the selection being expanded or reduced (REQ-UI-MULTI-SELECT). Starting a **new** selection discards it: the panel is placed anew against the new anchor rectangle (REQ-UI-SELECTION-PANEL), and the player drags it again if they want it elsewhere.
+  - **Input.** The drag consumes its mouse events like every other event over the panel (REQ-UI-SELECTION-PANEL): the press, the movement, and the release never reach the game world, so dragging the header neither box-selects (REQ-UI-MULTI-SELECT) nor places belts (REQ-BLD-BELT-DRAG). The drag continues while the cursor moves outside the panel or outside the view, and ends when the left button is released, wherever that happens. A press and release on the header without movement moves nothing and has no other effect.
+  - **Presentation only.** Moving the panel is not a player command: it never enters the replay stream and has no effect on the simulation, consistent with the controls panel's collapsed state (REQ-UI-CONTROLS-PANEL). The desired position is not saved to disk.
+- REQ-UI-PANEL-MODAL: **A modal opened from the selection panel opens on the panel.** A modal the player opens from a control inside the selection panel is placed **centered on the panel's current rectangle** rather than centered on the game window, so it appears where the player is already looking and under the cursor that just clicked the control. This is the same reason the panel itself is placed beside the selection instead of at a fixed corner (REQ-UI-SELECTION-PANEL): a modal centered on the window sends the cursor back across the view and then back again. Two modals are opened from the panel — the recipe/schematic selection dialog (REQ-UI-SELECT-BUTTON), from the selection button; and the layout configuration dialog (REQ-MOD-UI-DIALOG), both from the "Configure" button (REQ-MOD-UI-PREVIEW) and when it opens automatically after a schematic change (REQ-MOD-UI-AUTO-DIALOG).
+  - **The panel's rectangle as it currently stands.** The modal is centered on where the panel actually is when the modal opens: the position resolved from the anchor rectangle (REQ-UI-SELECTION-PANEL) or, once the player has dragged the panel, the position they dragged it to (REQ-UI-SELECTION-PANEL-DRAG). The panel is always shown when one of these modals opens, since the modal is opened from a control within it (REQ-UI-EMPTY-SELECTION).
+  - **Kept inside the game window.** Should the modal, centered that way, extend past an edge of the game window, it is pushed back inside; its size is never changed to make it fit. A modal larger than the window in a dimension is instead aligned with the window's top or left edge in that dimension, so the part read first stays visible.
+  - **Placement is all that changes.** The modal is modal as before, pauses the game and restores the speed on close as before (REQ-UI-SELECT-BUTTON, REQ-MOD-UI-DIALOG), shows the dim over the entire window including the panel it sits on (REQ-UI-MODAL-DIM), and is dismissed the same way. That it covers the panel costs nothing: while it is open the panel is dimmed and takes no input anyway.
+  - **Only these modals.** Every other modal is placed as before, centered on the game window: the escape menu (REQ-UI-GAME-MENU), the blueprint save and selection dialogs (REQ-UI-BLUEPRINT-CREATE, REQ-UI-BLUEPRINT-DIALOG), and the schematic choice dialog (REQ-DEF-SCHEMATIC-DROP), none of which is opened from the panel. So is a modal opened from another modal rather than from the panel — the Create Blueprint name dialog within the layout configuration dialog (REQ-MOD-UI-BLUEPRINT-CREATE) — which is placed against the modal that opened it.
+  - **Presentation only.** The placement is computed once, when the modal opens, and is not revisited while it is open; the panel cannot move meanwhile, being behind the modal and receiving no input. It is not a player command, never enters the replay stream, and has no effect on the simulation.
+- REQ-UI-MODAL-DIM: While a modal dialog, menu, or full-screen state screen is open on top of the game, a transparent black overlay (a dim/scrim) is drawn over the **entire game window** — the header bar, the game world view, and the widgets floating over it (the build button bar, REQ-UI-BUILD-BAR, the selection panel, REQ-UI-SELECTION-PANEL, and the controls panel, REQ-UI-CONTROLS-PANEL) — behind that modal, so the game reads as inactive while the modal holds focus. The overlay is shown for every modal that auto-pauses the simulation — the escape menu (REQ-UI-GAME-MENU), the recipe/schematic selection dialog (REQ-UI-SELECT-BUTTON), the layout configuration dialog (REQ-MOD-UI-DIALOG), the schematic choice dialog (REQ-DEF-SCHEMATIC-DROP), the blueprint save dialog (REQ-UI-BLUEPRINT-CREATE), and the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG) — as well as the game-over screen (REQ-HQ-GAME-OVER) and the win screen (REQ-WIN-SCREEN), which end rather than pause the game. When modals are nested (for example the Create Blueprint name dialog (REQ-MOD-UI-BLUEPRINT-CREATE) opened from the layout configuration dialog), only a single dim is shown over the game window; nested modals do not stack additional overlays. The same applies when one modal hands directly off to another — the blueprint save dialog opening the blueprint selection dialog on confirm (REQ-UI-BLUEPRINT-CREATE): the dim persists across the handoff rather than flickering off and back on, and the simulation is not resumed in between. The dim color and opacity are read from `visuals.toml [overlays]` (a semi-transparent black modal-dim color), consistent with the other overlay colors. The overlay is presentation-only and has no effect on the simulation.
+
+- REQ-UI-DIALOG-DISMISS: **Q dismisses an open dialog.** The key that backs the player out in the game world (REQ-UI-HOTKEYS) does the same on a dialog: while one is open it dismisses that dialog, doing exactly what its own Cancel or close already does and nothing else. It is a second key alongside Escape rather than a new behavior, so the player backs out of a dialog with the key their hand is already on. Three dialogs take it:
+  - **The recipe/schematic selection dialog** (REQ-UI-SELECT-BUTTON) — closes with the current recipe or schematic unchanged.
+  - **The blueprint selection dialog** (REQ-UI-BLUEPRINT-DIALOG) — closes with no other effect, as its close button does.
+  - **The layout configuration dialog** (REQ-MOD-UI-DIALOG) — Q is its Cancel, discarding every change made in this dialog session. Here Q backs out **one step at a time**, as it does in the game world: while a module is selected for placement (REQ-MOD-PLACEMENT) it clears that selection, while remove mode is active (REQ-MOD-REMOVE) it leaves remove mode, and only with neither active does it cancel the dialog. One press therefore never both leaves a mode and discards the session.
+
+  In each case the simulation speed is restored as it is on any other close (REQ-UI-SELECT-BUTTON, REQ-MOD-UI-DIALOG, REQ-UI-BLUEPRINT-DIALOG), and a dialog opened from another (REQ-MOD-UI-BLUEPRINT-CREATE) is dismissed before the one that opened it, Q reaching whichever holds focus.
+
+  **Where Q is not a dismissal.** It stays an ordinary character in the two dialogs that take a typed name — the blueprint save dialog (REQ-UI-BLUEPRINT-CREATE) and the Create Blueprint name dialog of the layout configuration dialog (REQ-MOD-UI-BLUEPRINT-CREATE) — where a dismissal key would be unable to tell a name from a command. The escape menu (REQ-UI-GAME-MENU) keeps Escape and its Continue button, the game-over and win screens (REQ-HQ-GAME-OVER, REQ-WIN-SCREEN) are ended by their own buttons, and the schematic choice dialog is not dismissible at all (REQ-DEF-SCHEMATIC-DROP).
 
 ### Game World
 
@@ -468,17 +510,17 @@ The screen is divided into two columns: a main column (75% width) containing the
 
   Because the contest-zone boundaries shift as the scrollable area grows with each push (REQ-GW-PUSH-EXPAND, REQ-GW-SCROLL-LIMIT), the ramp bands are recomputed from the current contest-zone boundaries. This is a presentation-only concern and does not affect the simulation, consistent with REQ-UI-NO-ZOOM.
 - REQ-UI-WORLD-ICON: In the game world, a building is drawn with an icon's glyph symbol centered on its footprint, in place of the letter identity glyph. The icon is an SVG loaded from `data/icons/buildings/`; only the icon's glyph is drawn in the world — in a contrasting ink (white over dark fills, dark over light fills) so it stays legible — and its colored chip background is omitted, because the footprint is already filled with the building's `visuals.toml` fill color. This applies to the production buildings (Miner, Smelter, Assembler, Reprocessing Plant, Shipyard, Salvage Bay), the HQ, and the player and enemy defence stations, wherever the identity label appears: operational buildings, construction sites (REQ-UI-CONSTRUCTION-PROGRESS), and the builder-mode and blueprint-placement ghosts. **Belts, splitters, and tunnels are excluded** — they keep their existing tile rendering so their orientation and flow stay readable (a centered icon would obscure direction). Their build-menu buttons still use icons (REQ-UI-BUILD-ICON); in particular the shared Tunnel button's `tunnel_entry.svg` is a build-button icon only, not a world icon. The directional output-port glyphs (REQ-UI-PORT-GLYPH, REQ-UI-PORT-TARGET-GLYPH) are a separate indicator and are unaffected. A building or station with no icon file falls back to its `visuals.toml` text glyph; a type with neither icon nor glyph shows no identity label. A missing icon is not an error, consistent with REQ-UI-BUILD-ICON.
-- REQ-UI-ITEM-ICON: In the game world, an item is drawn with its **item icon** in place of the colored square of REQ-GW-TILE-SIZE. The icon is a self-contained, full-color SVG (rendered as-is, unlike the glyph-only building icons of REQ-UI-WORLD-ICON), loaded at runtime from `data/icons/items/` — a sibling of the config directory, read the same way as the building icons (REQ-UI-BUILD-ICON) — one file per item type named after the item's id (e.g. `iron_ore.svg`). It fills the item's half-tile rect, keeping the size, spacing, and draw-order rules of REQ-GW-TILE-SIZE, and applies wherever an item is drawn: on belts, splitters, and tunnel ends, and while emerging from or sinking into a building port (REQ-MAT-OUTPUT-EMERGE, REQ-MAT-INPUT-INTAKE). An item type with no icon file falls back to its `visuals.toml` colored square (`fill` + `outline`); a missing icon is not an error, consistent with REQ-UI-BUILD-ICON. For performance, each item icon is rasterized to a pixmap cached per target pixel size — re-rasterized only when the tile pixel size changes (e.g. on view resize) — rather than re-rendered from vector every frame.
+- REQ-UI-ITEM-ICON: In the game world, an item is drawn as its `visuals.toml` colored square (`fill` + `outline`, the square of REQ-GW-TILE-SIZE) carrying its **item icon** on top. The square is drawn for every item, with or without an icon: it is what gives the item contrast against the tile beneath it, and its outline is what separates neighbouring items where they overlap on a belt. The icon is a self-contained, full-color SVG (rendered as-is, unlike the glyph-only building icons of REQ-UI-WORLD-ICON), loaded at runtime from `data/icons/items/` — a sibling of the config directory, read the same way as the building icons (REQ-UI-BUILD-ICON) — one file per item type named after the item's id (e.g. `iron_ore.svg`). The square fills the item's half-tile rect, keeping the size, spacing, and draw-order rules of REQ-GW-TILE-SIZE; the icon is drawn **inset** within that rect so a frame of the square's color stays visible all around it — required because each icon's viewBox is cropped tight to its artwork, so an icon drawn at the full rect would cover the square entirely. This applies wherever an item is drawn: on belts, splitters, and tunnel ends, and while emerging from or sinking into a building port (REQ-MAT-OUTPUT-EMERGE, REQ-MAT-INPUT-INTAKE). An item type with no icon file shows the colored square alone; a missing icon is not an error, consistent with REQ-UI-BUILD-ICON. **The colored square travels with the icon into the UI.** Wherever the UI displays an item *as an item* — the selection panel's item chips (REQ-UI-SINGLE-SELECTION, REQ-UI-HQ-PANEL), the recipe summary's input and output icons (REQ-UI-RECIPE-SUMMARY), and those same icons wherever a recipe is drawn in that form: on the selection dialog's option buttons (REQ-UI-SELECT-OPTIONS), in the item production tooltip (REQ-UI-ITEM-TOOLTIP), and in the unlock-choice dialog's recipe lines (REQ-DEF-SCHEMATIC-DROP) — the icon is drawn on that same square, by the same rules: the item's `fill` and `outline` from `visuals.toml`, the icon inset within the square so a frame of the square's color stays visible all around it, and the square alone when the item has no icon file. The square fills the rect the display allots to the icon, as it fills the half-tile rect in the world. One item therefore reads the same in a panel as it does on a belt. The one exception is an **inline icon standing in for the item's name beside a number** on a line of text: the `building_block` icon in place of the word `Blocks` (REQ-UI-BLOCKS-ICON, REQ-UI-EXPAND-BUTTON, REQ-UI-BUILD-COST, REQ-UI-MULTI-SELECTION, REQ-UI-BLUEPRINT-CARD), and the `scrap` icon in place of the word `Scrap` in the debris panel's remaining-scrap value (REQ-UI-DEBRIS-PANEL, REQ-UI-FIELD-MULTI-SELECTION). There the icon is a decoration on a line of text rather than an item display: it is drawn bare, without the square, and sized to the height of the text it sits in. Where the same value is instead shown *as an item* it keeps the square, as the HQ's block stock chip does beside the header bar's bare block icon (REQ-UI-HQ-PANEL). For performance, each item icon is rasterized to a pixmap cached per target pixel size — re-rasterized only when the tile pixel size changes (e.g. on view resize) — rather than re-rendered from vector every frame.
 - REQ-UI-CONSTRUCTION-PROGRESS: Construction sites display the building's identity symbol centered on the footprint (same as an operational building) — its icon glyph, or the text glyph as a fallback (REQ-UI-WORLD-ICON). Below the symbol — or centered on the footprint if the building has neither an icon nor a glyph — a construction progress percentage is shown (integer, e.g. `42%`), increasing from 0% to 100% as construction completes.
 - REQ-UI-PORT-GLYPH: Every output port of every building is indicated by a directional glyph drawn on the port's tile. The glyph is a `>` rotated to face the port's exit direction (`>` for East, `^` for North, `<` for West, `v` for South). It is drawn at the midpoint between the tile center and the tile edge that the port exits through (i.e. halfway from center toward the exit edge). The indicator is rendered for all building states: operational buildings, construction sites, and the builder-mode ghost. Buildings with multiple output ports (e.g. splitters) show one indicator per port.
 - REQ-UI-PORT-TARGET-GLYPH: While in builder mode (REQ-BLD-BUILDER-MODE), the builder-mode ghost additionally shows, for each of the building's output ports, a directional glyph drawn centered in the port's **target cell** — the cell immediately outside the footprint that the port pushes into, i.e. the cell the surface-mask output-port indicator occupies (see Surface Mask Format). As in REQ-UI-PORT-GLYPH the glyph is a `>` rotated to face the port's exit direction (`>` East, `^` North, `<` West, `v` South), previewing where the port's output will go before placement. This is in addition to the on-tile port glyph of REQ-UI-PORT-GLYPH, and — unlike that indicator — is shown only for the builder-mode ghost, not for operational buildings, construction sites, or the blueprint-placement ghost (REQ-UI-BLUEPRINT-PLACE). A building with multiple output ports (e.g. a splitter) shows one target-cell glyph per port. The target-cell glyph is drawn larger than the on-tile port glyph so it stands out as the flow-direction preview. Exceptions: the Tunnel Entry shows no target-cell glyph, because it receives items (which may arrive from any of its non-mouth edges, REQ-BLD-TUNNEL-ENTRY) rather than emitting into a single adjacent cell; the Shipyard shows none either, because its output port is a ship-spawn point (REQ-SHP-SPAWN-PLAYER) rather than a belt-item output (REQ-MAT-OUTPUT-EMERGE).
 - REQ-UI-STATUS-LIGHT: Every operational production building — Miner, Smelter, Assembler, Reprocessing Plant, Shipyard, and Salvage Bay — renders a small **status light**: a filled circle with a black outline drawn in the building's upper-right corner, letting the player read a building's production state without selecting it. The light is anchored to the footprint corner that is the upper-right corner in the building's default orientation and rotates with the building — like the output-port glyph (REQ-UI-PORT-GLYPH) — so it stays on the same physical corner of the building as it is rotated. The status light is rendered only for operational buildings; construction sites (which instead show construction progress, REQ-UI-CONSTRUCTION-PROGRESS) and the builder-mode ghost do not render it. Buildings that are not production buildings — belts, splitters, tunnel entries/exits, and the HQ — have no status light. The black outline is constant; the fill color reflects the building's current production state.
   - For the five production buildings (Miner, Smelter, Assembler, Reprocessing Plant, Shipyard), the fill color is determined by evaluating, in order:
-    - **Grey** — no recipe or schematic is selected. This applies only to buildings with a player-facing selection (Miner, Assembler, Shipyard); the Smelter and Reprocessing Plant always run an implicit recipe (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING) and are never grey.
+    - **Grey** — no recipe or schematic is selected. Every production building can show it, an auto-recipe building included: it is grey until something is offered at an input port for it to select a recipe from, and again whenever the player hands it back to automatic selection (REQ-BLD-AUTO-RECIPE).
     - **Green** — the building is currently producing: a production cycle is active (REQ-MAT-CYCLE; for the Shipyard, an in-progress production cycle per REQ-BLD-SHIPYARD).
-    - **Red** — the building is idle because a required input is missing from its input buffers, so it cannot start a cycle. Missing input takes precedence over a full output buffer: if any required input is missing the light is red even when the output buffer is also full.
-    - **Yellow** — the building is idle with all required inputs present but its output buffer full, so no new cycle can start (REQ-MAT-OUTPUT-BUFFER, REQ-MAT-CYCLE).
-    - A configured building that is momentarily idle yet blocked by neither condition (all inputs present and the output buffer has room — a transient state that resolves into a started cycle on the same or the next tick per REQ-MAT-CYCLE) shows green.
+    - **Red** — the building is idle because a required input is missing from its input buffers, so it cannot start a cycle. Missing input takes precedence over a blocked output side: if any required input is missing the light is red even when an output buffer is also out of room.
+    - **Yellow** — the building is idle with all required inputs present but the output side cannot take the cycle: at least one item the cycle could produce has no room in its own buffer, so no new cycle can start (REQ-MAT-OUTPUT-BUFFER, REQ-MAT-CYCLE). A buffer short of a full cycle's worth of free space blocks just as a completely full one does.
+    - A configured building that is momentarily idle yet blocked by neither condition (all inputs present and room for every output the cycle could produce — a transient state that resolves into a started cycle on the same or the next tick per REQ-MAT-CYCLE) shows green.
   - The Salvage Bay has no recipe and no production cycle (REQ-BLD-SALVAGE-BAY); its status light uses only two states: **green** while its output buffer holds at least one unit of scrap, and **red** while its output buffer is empty. The Salvage Bay's status light is never grey or yellow.
   - The four fill colors (grey, green, red, yellow) and the outline color are read from `visuals.toml [status_light]`, consistent with the other rendering-only colors. The status light is presentation-only and has no effect on the simulation.
 - REQ-UI-HP-BARS: All entities with HP — the HQ, player and enemy defence stations, and player and enemy ships — render an HP bar below them. The bar is always visible regardless of current HP. The bar's filled portion represents the fraction of current HP to maximum HP.
@@ -488,17 +530,25 @@ The screen is divided into two columns: a main column (75% width) containing the
   - **W** — increases game speed by one step in the sequence 0×, 0.5×, 1×, 2×, 10× (no wrap-around past 10×).
   - **S** — decreases game speed by one step in the same sequence (no wrap-around past 0×).
   - **A / D** — scroll the view left / right (REQ-UI-SCROLL).
-  - **Q** — context-sensitive. If a build mode is active (builder mode or blueprint placement mode), pressing Q exits it. Otherwise, pressing Q toggles deconstruct mode: it enters deconstruct mode if inactive, or exits deconstruct mode if already active. (See also REQ-UI-DECONSTRUCT-BUTTON for the equivalent button.)
+  - **Q** — context-sensitive: one key that backs out of whatever the player is currently in, and enters deconstruct mode when they are in nothing. Its cases are evaluated in order:
+    - A dialog that takes Q is open — Q dismisses it, and the cases below do not apply: the dialog holds focus, and the game world is not what the player is backing out of (REQ-UI-DIALOG-DISMISS).
+    - A build mode is active (builder mode, blueprint placement mode, or deconstruct mode) — Q exits it.
+    - Something is selected — Q clears the selection (REQ-UI-EMPTY-SELECTION). The two cases never both apply, a selection and a build mode being mutually exclusive (REQ-UI-SELECTION-EXCLUSIVE); the order is stated only to fix the reading.
+    - Neither — Q enters deconstruct mode (see also REQ-UI-DECONSTRUCT-BUTTON for the equivalent button, which enters it from any of these states and clears the selection in doing so).
+
+    Entering deconstruct mode by keyboard while holding a selection therefore takes two presses — the first clears it, the second enters the mode — whereas the Deconstruct button does it in one click.
   - **R / Shift+R** — in builder mode, rotate the ghost counter-clockwise / clockwise (REQ-BLD-ROTATE).
   - **C** — create a temporary blueprint from the current selection and enter its placement mode (REQ-UI-BLUEPRINT-TEMP). Has effect only when at least one player-placeable building is selected; otherwise it does nothing.
   - **V** — re-enter placement mode for the last temporary blueprint created with C (REQ-UI-BLUEPRINT-TEMP). Does nothing when no temporary blueprint exists.
   - **Ctrl+C** — save the current selection as a named blueprint: opens the blueprint save dialog (REQ-UI-BLUEPRINT-CREATE). Has effect only when at least one player-placeable building is selected; otherwise it does nothing.
   - **Ctrl+V** — opens the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG), from which a saved blueprint is picked for placement. It is available whenever the game is being played, regardless of the current selection or of which build mode is active, and opens the dialog even when no blueprints are saved yet.
-  - **Escape** — opens the escape menu (REQ-UI-GAME-MENU). While a blueprint dialog is open, Escape closes that dialog instead (REQ-UI-BLUEPRINT-DIALOG).
+  - **Escape** — opens the escape menu (REQ-UI-GAME-MENU). While a dismissible dialog is open, Escape closes that dialog instead — the blueprint dialogs (REQ-UI-BLUEPRINT-DIALOG) and the two dialogs Q also dismisses (REQ-UI-DIALOG-DISMISS). The schematic choice dialog is the exception it cannot close (REQ-DEF-SCHEMATIC-DROP).
   - **Build mode selection** — pressing a build hotkey activates builder mode for the corresponding building type, equivalent to clicking its build button (REQ-BLD-BUILDER-MODE):
     - **1** — Belt, **2** — Splitter, **3** — Tunnel (the unified tunnel build mode, REQ-BLD-TUNNEL-MODE). Hotkey 4 is unused.
     - **Shift+1** — Miner, **Shift+2** — Smelter, **Shift+3** — Assembler, **Shift+4** — Shipyard, **Shift+5** — Salvage Bay, **Shift+6** — Reprocessing Plant.
 
+  These shortcuts are the definition; the controls panel (REQ-UI-CONTROLS-PANEL) displays the subset of them that applies to the player's current situation, and the build buttons carry the build hotkeys on their badges (REQ-UI-BUILD-COST). Neither display defines a binding of its own.
+
 ### Debug Draw
 
 - REQ-UI-DEBUG-DRAW: A debug draw mode can be toggled on and off with the **F3** key. It is inactive by default. While active, the sensor range of every ship — both player and enemy — is drawn as a circle centered on the ship, using that ship schematic's outline color from `visuals.toml`.
@@ -518,24 +568,81 @@ The screen is divided into two columns: a main column (75% width) containing the
   - **Quit** — closes the application.
   Pressing Escape while the escape menu is open is equivalent to clicking Continue.
 
-### Selected Building Panel
+### Selection Panel
 
-- REQ-UI-EMPTY-SELECTION: When nothing is selected (no building, construction site, ship, defence station, or piece of debris), the panel is empty.
+The selection panel shows the details of the current selection, whatever its category (REQ-UI-SELECTION-CATEGORIES): buildings and construction sites, ships, defence stations, and debris. Its position, size, and overlay behavior are defined in REQ-UI-SELECTION-PANEL; the requirements below define its content.
+
+The panel shows exactly one **content** at a time, picked from the catalog in REQ-UI-SELECTION-CONTENT by what is selected. Every content is assembled from the same small set of parts and follows the same card structure (REQ-UI-SELECTION-CARD), so different selections read alike and a part means the same thing wherever it appears.
+
+- REQ-UI-EMPTY-SELECTION: When nothing is selected (no building, construction site, ship, defence station, or piece of debris), the selection panel is not shown at all — it is hidden rather than shown empty, so the full game world view is visible (REQ-UI-SELECTION-PANEL). It reappears as soon as an object is selected.
 - REQ-UI-SELECTION-CATEGORIES: **Selection categories and precedence.** Every selectable object belongs to one of two mutually exclusive selection categories: **buildings** (buildings and construction sites) and **field objects** (ships and defence stations — player or enemy — together with debris). A single selection holds objects from only one category at a time. Field objects of different kinds may be selected together (e.g. several ships plus debris, freely mixing player and enemy actors). Buildings are exclusive and take precedence — **buildings win**: selecting a building (by click, Ctrl+click, or a box-drag covering at least one building) clears any field selection and yields a buildings-only selection, and conversely selecting any field object clears any building selection. Point hit-testing prefers a building over a coincident field object, and among field objects prefers an actor (ship or defence station) over a coincident piece of debris (REQ-UI-ENTITY-CLICK-SELECT, REQ-UI-DEBRIS-CLICK-SELECT).
-- REQ-UI-SINGLE-SELECTION: When one building is selected, the panel shows: building name, current recipe or schematic selection, input buffer contents, and output buffer contents. Buffer counts are displayed as `a/b` where `a` is the current item count and `b` is the per-cycle amount (items consumed per run for inputs; items produced per run for outputs). For a selected construction site, the recipe/schematic selection (and, for a shipyard, the layout preview and "Configure" button) are shown but the buffer rows are omitted (REQ-BLD-SITE-CONFIG).
-- REQ-UI-PRODUCTION-PROGRESS: For buildings that produce items or ships (miner, smelter, assembler, reprocessing plant, shipyard), the selected building panel also shows: (a) the cycle time of the currently selected recipe or schematic in seconds, and (b) the completion percentage of the active production cycle as an integer (e.g. `42%`), or the text `idle` when no production cycle is active. When no recipe or schematic is selected, neither the cycle time nor the progress indicator is shown.
+- REQ-UI-SELECTION-EXCLUSIVE: **A selection and a build mode are mutually exclusive.** At any moment the player is either holding a selection or in one of the build modes — builder mode (REQ-BLD-BUILDER-MODE), blueprint placement mode (REQ-UI-BLUEPRINT-MODE), or deconstruct mode (REQ-UI-DECONSTRUCT-BUTTON) — never both. **Entering any build mode clears the selection**, whichever way the mode is entered: a build button, a build hotkey, the Deconstruct button, the Q deconstruct toggle, C, or picking a blueprint card (REQ-UI-HOTKEYS, REQ-UI-BLUEPRINT-TEMP, REQ-UI-BLUEPRINT-DIALOG). Switching directly from one build mode to another therefore has no selection left to clear. The converse direction needs no rule of its own: while a build mode is active there is no gesture that selects — a left click places, marks for demolition, or transfers settings instead (REQ-BLD-BUILDER-MODE, REQ-BLD-DECONSTRUCT-CLICK, REQ-UI-BLUEPRINT-TRANSFER) — so a selection can only be made after the mode is left.
+  - **A selection is read before it is cleared.** The gestures that act on the selection and then enter a mode capture it first: C builds its temporary blueprint from the selection and only then enters placement mode (REQ-UI-BLUEPRINT-TEMP), and Ctrl+C's save dialog creates its blueprint before the selection dialog it opens can start a placement (REQ-UI-BLUEPRINT-CREATE). Neither loses what it was invoked on.
+  - **What follows from it.** The selection panel is never shown while a build mode is active, being hidden on an empty selection (REQ-UI-EMPTY-SELECTION), and the world draws no selection outlines there. The controls panel's contexts (REQ-UI-CONTROLS-CONTENT) become a partition of the state rather than a precedence rule: exactly one of General, Selection, Build, Blueprint, and Deconstruct applies, and the Selection context's "no build mode active" clause restates the exclusivity instead of resolving an overlap. Nothing here reaches the simulation — selection and build mode are both presentation state, and clearing a selection is not a player command, never enters the replay stream, and has no effect on the simulation.
+- REQ-UI-SELECTION-CARD: **Card structure.** Every panel content is a card with the same three parts, top to bottom:
+  - **Header** — always shown. It holds the selection's identity symbol on the left — the building's icon glyph (REQ-UI-WORLD-ICON), a ship's schematic color swatch, or the kind symbol of a defence station or piece of debris — the selection's name beside it, and one optional **right slot**. The right slot holds a status indicator (REQ-UI-SELECTION-STATUS), a ship's current behavior (REQ-UI-SHIP-BEHAVIOR), or an object count — never more than one of them; which one applies is stated per content in REQ-UI-SELECTION-CONTENT. The header carries no control of its own, and doubles as the panel's drag handle (REQ-UI-SELECTION-PANEL-DRAG).
+  - **Configuration group** — the controls that change how the selected object is set up: the recipe/schematic selection control (REQ-UI-SELECT-BUTTON), a shipyard's layout preview and Configure button (REQ-MOD-UI-PREVIEW), and a splitter's output filters (REQ-BLD-SPLITTER). It is shown identically for an operational building and for a construction site of the same type (REQ-BLD-SITE-CONFIG).
+  - **Runtime group** — what the object is currently doing: buffer contents, production progress, HP, remaining scrap, and the belt clear action (REQ-UI-BELT-CLEAR). Where the object has **HP**, its bar is the first thing in this group, above everything else the card shows (REQ-UI-HQ-PANEL, REQ-UI-SHIP-STATS-PANEL, REQ-UI-STATION-STATS-PANEL) — how close the thing is to dying outranks what it is holding. For a **construction site** the entire runtime group is replaced by a captioned `Construction` section: a progress bar filled to the site's construction completion with that completion as an integer percentage beside the caption — the same value the world draws on the footprint (REQ-UI-CONSTRUCTION-PROGRESS) — followed by a note that buffers appear once the building is built, because a site has neither buffers nor a production cycle (REQ-BLD-SITE-CONFIG). That section sits **directly below the header, above the configuration group**, so how far along the site is reads first; the configuration group is otherwise unaffected and stays visible on a site.
+
+  A group with nothing to show takes no space, so a content may consist of a header alone. Within a group, related parts form **sections** carrying a short caption above them (e.g. `Layout`, `Input buffers`, `Production`, `Output buffers`); a section and its caption are shown only while that section has content, so e.g. a Miner (which consumes nothing) shows no input buffer section.
+- REQ-UI-SELECTION-CONTENT: **Content catalog.** Which content the panel shows follows from the selection alone:
+
+  | Selection | Header right slot | Configuration group | Runtime group |
+  |---|---|---|---|
+  | Miner, Assembler, Smelter, Reprocessing Plant | status | recipe control + recipe summary | buffers + production |
+  | Shipyard | status | schematic control + layout preview + Configure | buffers + production |
+  | Salvage Bay | status | — | buffers |
+  | HQ | — | — | block stock + HP |
+  | Belt, Tunnel Entry, Tunnel Exit | count | — | clear action |
+  | Splitter | — | output filters | clear action |
+  | Several buildings | — | — | type counts + total cost |
+  | One ship | behavior | — | HP + hull stats + module summaries |
+  | One defence station | — | — | HP + stats |
+  | Debris (one or several) | count | — | remaining scrap |
+  | Several mixed field objects | count | — | type counts + scrap total |
+
+  Selections sharing a row of this table get the same content and differ only in the name and symbol in the header. A count in the right slot appears only for an aggregated multi-selection (REQ-UI-SELECTION-AGGREGATE); a single selection of those types shows an empty slot.
+- REQ-UI-SELECTION-STATUS: **Status indicator.** For a building whose production state is already rendered in the world as a status light (REQ-UI-STATUS-LIGHT) — Miner, Smelter, Assembler, Reprocessing Plant, Shipyard, Salvage Bay — the header's right slot repeats that same state as a colored dot with a short caption beside it, so the panel and the world never disagree. The state is derived from the evaluation defined in REQ-UI-STATUS-LIGHT rather than from a second definition, and the dot uses that state's fill color from `visuals.toml [status_light]`. The captions name the state: `no recipe` (grey), `producing` (green), `missing input` (red), `output full` (yellow); for the Salvage Bay, `holding scrap` (green) and `empty` (red). A selected **construction site** shows the caption `constructing` with no dot, whatever its type. Buildings with no status light — belts, splitters, tunnel ends, the HQ — show nothing in the slot.
+- REQ-UI-SELECTION-AGGREGATE: **Aggregating a homogeneous multi-selection.** When several objects are selected and their content can be shown as one — the same content, with its values aggregated over the whole selection — the panel shows that single content with the number of selected objects in the header's right slot (`x<count>`), instead of the count summary of REQ-UI-MULTI-SELECTION / REQ-UI-FIELD-MULTI-SELECTION. This applies exactly where every part of the content aggregates:
+  - **Belt-subsystem tiles** — any mix of belts, tunnel entries, and tunnel exits. Their content is the clear action alone, which already acts on the whole selection (REQ-UI-BELT-CLEAR).
+  - **Debris** — several pieces of debris and nothing else. Their remaining scrap sums into one value (REQ-UI-DEBRIS-PANEL).
+
+  Every other multi-selection falls back to the count summary. In particular a selection mixing a splitter with belts does not aggregate (a splitter carries per-object output filters, which have no aggregate), and neither do several production buildings of one type (per-building buffers and cycle progress have no aggregate).
+- REQ-UI-SINGLE-SELECTION: When one building is selected, the panel shows its symbol and name in the header (REQ-UI-SELECTION-CARD), its current recipe or schematic selection (REQ-UI-SELECT-BUTTON) and recipe summary (REQ-UI-RECIPE-SUMMARY) in the configuration group, and its input and output buffer contents in the runtime group. Each buffered item is shown as an **item chip** bearing that item's icon on its colored square (REQ-UI-ITEM-ICON) and its current count, and hovering a chip shows that item's production tooltip (REQ-UI-ITEM-TOOLTIP):
+  - an **input** chip shows the per-cycle amount below the count (the items consumed per run, e.g. `/ 2 per cycle`), or the count alone when the building has no selected recipe or schematic to give one;
+  - an **output** chip shows the count against **that item's own** output buffer capacity as `a / b` (REQ-MAT-OUTPUT-BUFFER), with the item's name below. Each output chip therefore stands for one buffer, and a Reprocessing Plant shows one for every item any of its output groups can produce (REQ-MAT-OUTPUT-GROUP).
+
+  Input and output chips form separately captioned sections (REQ-UI-SELECTION-CARD). A section lists a chip for **every item the building's cycle involves**, whether or not the buffer currently holds any: an empty buffer reads `0` rather than its chip disappearing, so the card keeps one shape while the building runs. A section left with no chips at all is not shown. The production section (REQ-UI-PRODUCTION-PROGRESS) sits **between them**, so the card reads in the direction the materials flow: what goes in, what is being made of it, what has come out. For a selected construction site the buffer sections are omitted (REQ-BLD-SITE-CONFIG).
+
+  **Only unlocked items are listed.** Should a building's buffers carry an entry for an item the player cannot make yet, it is left out of both sections, consistent with the rest of the UI hiding what is not unlocked yet (REQ-LOCK-UI-RECIPE, REQ-LOCK-UI-SPLITTER).
+- REQ-UI-RECIPE-SUMMARY: Below the recipe/schematic selection control, a building running a recipe or schematic shows a one-line **recipe summary**: each input item's icon on its colored square (REQ-UI-ITEM-ICON) with its per-cycle amount and the inputs separated by `+`, an arrow, then what the recipe produces, and the cycle time in seconds. The output side lists each item of an output group with its icon and per-cycle amount, the items within a group separated by `+` as the inputs are — they are produced together — and the **groups separated by `/`**, since only one of them happens (REQ-MAT-OUTPUT-GROUP). A recipe with a single group therefore reads exactly as before, and a Reprocessing Plant's reads as the alternatives it is rather than as one combined yield. It restates what the building will do without opening the selection dialog, and it is the panel's only display of the cycle time. For a Shipyard the summary is built from the schematic's materials and production time including the placed modules' contributions (REQ-BLD-SHIPYARD, REQ-MOD-STAT-CALC), matching the buffers beneath it. A building with no recipe or schematic selected shows no summary — including an auto-recipe building that has yet to select one (REQ-BLD-AUTO-RECIPE), which shows none until it does and keeps it from then on, so the card does not resize in step with the building's status (REQ-UI-SELECTION-STATUS, REQ-UI-SELECTION-PANEL).
+- REQ-UI-PRODUCTION-PROGRESS: For buildings that produce items or ships (miner, smelter, assembler, reprocessing plant, shipyard), the panel's runtime group shows a captioned **production section** between the input and output buffer sections (REQ-UI-SINGLE-SELECTION): a horizontal progress bar filled to the completion of the active production cycle, with that completion beside the caption as an integer percentage (e.g. `72%`), or the text `idle` in place of the percentage and an empty bar when no production cycle is active. The cycle time is shown in the recipe summary (REQ-UI-RECIPE-SUMMARY) rather than repeated here. When no recipe or schematic is selected, the production section is not shown at all.
 - REQ-UI-MULTI-SELECT: The player selects multiple objects by box-drag or by Ctrl+clicking individual objects to add or remove them from the selection. Multi-select operates within a single category (REQ-UI-SELECTION-CATEGORIES). A box-drag that covers at least one building selects buildings (any field objects within the box are ignored — buildings win); a box-drag that covers no building but does cover ships, defence stations, or debris selects all of those field objects together (REQ-UI-ENTITY-CLICK-SELECT, REQ-UI-DEBRIS-MULTI-SELECT).
-- REQ-UI-MULTI-SELECTION: When multiple buildings are selected, the panel shows how many of each building type are selected. No per-building detail is shown. The panel additionally shows the **total building block cost** of the selection — the sum of each selected building's placement cost (`buildings.toml [[building]].cost`, per REQ-BLD-COST), counting only player-placeable buildings (buildings with a button in the build button bar); non-player-placeable buildings (the HQ and defence stations) are excluded from the total, consistent with the blueprint total (REQ-UI-BLUEPRINT-CARD). Construction sites count at their building type's full placement cost regardless of construction progress.
-- REQ-UI-CONFIG-INLINE: Recipe and schematic configuration for a selected building is shown within this panel. Recipe selection (miner, assembler) and schematic selection (shipyard) use the selection button and dialog (REQ-UI-SELECT-BUTTON) rather than an inline control. For shipyards, the panel additionally shows the ship layout preview and "Configure" button below the schematic selection button (REQ-MOD-UI-PREVIEW).
-- REQ-UI-SELECT-BUTTON: **Recipe and schematic selection control.** Recipe selection (Miner ore type, Assembler recipe) and schematic selection (Shipyard) are each presented in the selected building panel as a single **selection button** whose caption is the name of the currently selected recipe or schematic, or a placeholder ("Select recipe" / "Select schematic") when none is selected. Clicking the button opens a modal **selection dialog** that pauses the game (speed set to 0×; on close, the speed is restored to what it was before the dialog was opened). The dialog contains a grid of option buttons, one per selectable option — only options that are currently unlocked are shown (REQ-LOCK-UI-RECIPE for recipes, REQ-LOCK-UI-SCHEMATIC for schematics). Hovering an option button shows the selection info tooltip (REQ-UI-SELECT-TOOLTIP). Clicking an option button selects that recipe/schematic, closes the dialog, and updates the selection button's caption in the selected building panel. The dialog can be dismissed without changing the current selection (e.g. closing it without clicking an option). Selecting a new recipe or schematic has the same effects as before (REQ-MAT-INPUT-BUFFER, REQ-MAT-OUTPUT-BUFFER, REQ-BLD-SHIPYARD).
-- REQ-UI-SELECT-TOOLTIP: **Selection info tooltip.** Hovering an option button in the selection dialog (REQ-UI-SELECT-BUTTON), and hovering the selection button in the selected building panel when a selection is set, displays an info tooltip:
-  - For a **recipe** (Miner or Assembler): the recipe name; the name and quantity of each input item (no inputs are listed for miner recipes, which consume nothing); the completion time (`duration_seconds`); and the name and quantity of the produced output item.
-  - For a **ship schematic** (Shipyard): the ship's `display_name`; the name and quantity of each base required material (`[ship.schematic].materials`, excluding any module contributions); the base production time (`[ship.schematic].production_time_seconds`); and "Produces: 1 <ship display name>".
-- REQ-UI-RECIPE-ICON: In the recipe-selection dialog (REQ-UI-SELECT-BUTTON) for a Miner or Assembler, each recipe option button shows the icon of the recipe's produced item **instead of** its name caption (icon-only). The item shown is the recipe's `icon` field if set, otherwise its first output item; the icon is that item's icon per REQ-UI-ITEM-ICON. When the item has no icon file, the button falls back to the recipe/item name caption. The recipe name and details remain available on hover via the selection info tooltip (REQ-UI-SELECT-TOOLTIP). The `(None)` option keeps its text caption. This applies only to recipe options; the Shipyard schematic-selection dialog is unaffected and continues to show ship name captions.
-- REQ-UI-BELT-CLEAR: When one or more belt, splitter, tunnel entry, or tunnel exit tiles are selected, the panel shows a "Clear" button that removes all items from the selected tiles. Clearing a tunnel entry or exit also discards all items currently in transit through that tunnel (REQ-BLD-TUNNEL-TRANSIT). This can be used to resolve stalled belts, splitters, and tunnels.
+  - **Rectangle geometry.** The box is **not** snapped to tiles: its two corners are the exact world positions the button went down at and the cursor is at now, so the rectangle is drawn where the mouse actually went and follows it pixel by pixel. The corners are held in world coordinates rather than screen ones, so the anchor stays on the spot in the world it was placed on when the view scrolls under a held button (REQ-UI-SCROLL).
+  - **Coverage.** What the box covers follows the same rectangle, not the tiles it touches. An object that occupies whole tiles — a building, a construction site, a defence station — is covered when the rectangle overlaps any of its body cells, so grazing a building's tile selects it. An object that has a position rather than a footprint — a ship, a piece of debris — is covered when the rectangle contains its centre, so what the player sees enclosed by the rectangle is exactly what the release selects. This is also what makes box and click agree: a click already hit-tests ships and debris against their world positions (REQ-UI-ENTITY-CLICK-SELECT, REQ-UI-DEBRIS-CLICK-SELECT), not against the tile they stand on.
+  - **When the rectangle appears.** The rectangle is drawn only once the cursor has moved at least **2 pixels** from the position the button went down at — a press alone draws nothing, so a plain click does not flash a rectangle. The threshold is in screen pixels because it only separates a click from a drag, which is a question of hand steadiness. Once shown, the rectangle stays shown for the rest of the drag, including when the cursor comes back to where it started. It is measured against where the anchor sits on screen at that moment, so scrolling the view while the button is held moves no cursor but still crosses the threshold, the box having grown all the same. Below the threshold the gesture is a click, and the box it resolves on release is the **whole tile** the button went down on — that is what makes a click select or mark what it points at (REQ-UI-SELECTION-CATEGORIES, REQ-BLD-DECONSTRUCT-CLICK) rather than the empty rectangle a motionless cursor spans.
+  - **Rectangle color.** While dragging, the selection rectangle is drawn as an outline in `visuals.toml [overlays].selected_outline` — the same color and config entry as the outline drawn in the world around the objects that end up selected, so the box and the selection it produces read as one thing. **Exception:** while deconstruct mode is active (REQ-UI-DECONSTRUCT-BUTTON, REQ-UI-HOTKEYS), the box drag marks buildings for demolition instead (REQ-BLD-DECONSTRUCT-BOX) and the rectangle is drawn in the deconstruct color — the RGB of `visuals.toml [overlays].deconstruct_tint`, drawn **fully opaque**. That entry's alpha channel governs only the fills it tints (the deconstruct-mode hover tint and queued buildings, REQ-UI-DECONSTRUCT-BORDER, REQ-BLD-DECON-QUEUE) and is not applied to this outline, which would otherwise be too faint to see. The rectangle's geometry is the same in both modes.
+- REQ-UI-MULTI-SELECTION: When multiple buildings are selected and the selection does not aggregate (REQ-UI-SELECTION-AGGREGATE), the panel shows a count summary. Its header names the size of the selection as `<n> buildings` in place of an object name, and carries no symbol and nothing in its right slot. Below it is one row per selected building type — the type's symbol, its name, and the number selected as `x<count>` — one type per row, and no per-building detail. A final row shows the **total building block cost** of the selection, captioned `Total cost` with the value followed by the `building_block` item icon (REQ-UI-BLOCKS-ICON, REQ-UI-ITEM-ICON): the sum of each selected building's placement cost (`buildings.toml [[building]].cost`, per REQ-BLD-COST), counting only player-placeable buildings (buildings with a button in the build button bar); non-player-placeable buildings (the HQ and defence stations) are excluded from the total, consistent with the blueprint total (REQ-UI-BLUEPRINT-CARD). Construction sites count at their building type's full placement cost regardless of construction progress.
+- REQ-UI-CONFIG-INLINE: Recipe and schematic configuration for a selected building is shown within this panel, in its configuration group (REQ-UI-SELECTION-CARD). Recipe selection (miner, assembler, smelter, reprocessing plant) and schematic selection (shipyard) use the selection button and dialog (REQ-UI-SELECT-BUTTON) rather than an inline control. For shipyards, the panel additionally shows the ship layout preview and "Configure" button below the schematic selection button (REQ-MOD-UI-PREVIEW).
+- REQ-UI-SELECT-BUTTON: **Recipe and schematic selection control.** Recipe selection (Miner ore type, Assembler recipe, and the Smelter's and Reprocessing Plant's recipe per REQ-BLD-AUTO-RECIPE) and schematic selection (Shipyard) are each presented in the selection panel as a single **selection button** whose caption is the name of the currently selected recipe or schematic, or a placeholder ("Select recipe" / "Select schematic") when none is selected. Clicking the button opens a modal **selection dialog** that pauses the game (speed set to 0×; on close, the speed is restored to what it was before the dialog was opened) and that opens centered on the selection panel, as every modal opened from the panel does (REQ-UI-PANEL-MODAL). The dialog contains a vertical list of option buttons, one per selectable option, each describing itself (REQ-UI-SELECT-OPTIONS) — only options that are currently unlocked are shown (REQ-LOCK-UI-RECIPE for recipes, REQ-LOCK-UI-SCHEMATIC for schematics). Neither the option buttons nor the selection button carries a tooltip: an option button states what it makes on its own face, and what the building has selected is drawn beneath the selection button as the recipe summary (REQ-UI-RECIPE-SUMMARY), with the production paths of the items involved reachable by hovering the card's item chips (REQ-UI-ITEM-TOOLTIP). Clicking an option button selects that recipe/schematic, closes the dialog, and updates the selection button's caption in the selection panel. The dialog can be dismissed without changing the current selection — by closing it without clicking an option, by Escape, or by Q (REQ-UI-DIALOG-DISMISS). Selecting a new recipe or schematic has the same effects as before (REQ-MAT-INPUT-BUFFER, REQ-MAT-OUTPUT-BUFFER, REQ-BLD-SHIPYARD).
+- REQ-UI-SELECT-OPTIONS: **Option list of the selection dialog.** The selection dialog (REQ-UI-SELECT-BUTTON) lists its options as a **single vertical column** of buttons, one per option, rather than a grid: each button is as wide as the dialog and states what the option does, which needs a line of its own. No option button carries a tooltip — the button face is the whole description, so the player reads every option's inputs, product, and time from the list itself without hovering anything. Should the column be taller than the space the window leaves the dialog — a fully unlocked Assembler offers more options than any window can hold, and a modal is never resized to fit (REQ-UI-PANEL-MODAL) — the list **scrolls** within the dialog rather than the dialog growing past the window.
+  - A **recipe** option shows the **recipe name** on its first line and, beneath it, that recipe drawn as the recipe summary line draws it (REQ-UI-RECIPE-SUMMARY): each input item's icon on its colored square with its per-cycle amount, an arrow, its output groups with their amounts, and the cycle time. A miner recipe consumes nothing, so its line begins at the arrow.
+  - A **ship schematic** option (Shipyard) shows the ship's `display_name` on its first line and, beneath it, the icons and quantities of its base required materials (`[ship.schematic].materials`, excluding any module contributions) with the base production time (`[ship.schematic].production_time_seconds`). A ship is not an item and has no icon of its own, so this line names no output: the button's caption is what it produces.
+  - The `(None)` option shows its text caption alone. On an auto-recipe building it is captioned `(Auto)` instead, because there it does not leave the building idle but returns it to automatic selection (REQ-BLD-AUTO-RECIPE).
+- REQ-UI-ITEM-TOOLTIP: **Item production tooltip.** Hovering an item chip in the selection panel — an input or output buffer chip (REQ-UI-SINGLE-SELECTION) or the HQ's block stock chip (REQ-UI-HQ-PANEL) — shows a tooltip telling the player where that item comes from. It has a heading and a body:
+  - the heading is the **hovered item's name**. For an input chip this is the only place the item is named at all, since such a chip carries a count and no name (REQ-UI-SINGLE-SELECTION).
+  - the body is the caption `Produced by` followed by one **recipe line** per unlocked recipe that produces the item. A recipe line is a small **card** of two rows: the icon of the building that runs the recipe (REQ-UI-BUILD-ICON) and the recipe's name on the first, and the recipe itself on the second, drawn as the recipe summary draws it (REQ-UI-RECIPE-SUMMARY) — each input item's icon on its colored square with its per-cycle amount, the inputs separated by `+`, an arrow, its output groups with their amounts, and the cycle time. Two rows rather than one because an identity and a cycle read as different things, and a single row of icons, names and numbers runs too long to scan; a card around each because several producers stacked as bare lines read as one field of icons and numbers rather than as separate recipes. A line drawn where its surroundings already frame it — on an option button (REQ-UI-SELECT-OPTIONS), or as the panel's recipe summary — takes no card of its own. An item may have several producers — an iron ingot is smelted from ore, smelted from scrap, and recovered by reprocessing — and the building icon and recipe name are what tell those lines apart and tell the player which building to place for which path.
+
+  **Only recipes the player can run are listed**, consistent with the rest of the UI hiding what the player cannot make yet. What that means differs by building, because only Miner and Assembler recipes are unlocked individually (REQ-LOCK-UI-RECIPE): those are listed once unlocked, while a Smelter's or Reprocessing Plant's recipes (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING) are listed once **their building** is unlocked (REQ-LOCK-BUILDING) — there is no sense in naming a path through a plant the player cannot place. Two cases have no recipe line to show, and each says so in place of the list rather than leaving the tooltip bare:
+  - **An item no recipe produces at all.** Scrap is salvaged from debris (REQ-RES-DEBRIS-DROP) rather than crafted, so its tooltip reads `Salvaged from debris` in place of the `Produced by` caption and lists nothing beneath it.
+  - **An item whose every producing recipe is still locked.** The caption stays `Produced by`, and the single line beneath it reads `Undiscovered`: the player is told the item is made somehow, without being shown a path they have not unlocked yet.
+
+  The tooltip belongs to item chips only. The selection dialog shows no tooltips at all, its buttons describing themselves (REQ-UI-SELECT-OPTIONS), and the icons of the recipe summary line (REQ-UI-RECIPE-SUMMARY) show none either: they are parts of one line that already describes one recipe, rather than standalone item displays.
+- REQ-UI-BELT-CLEAR: When one or more belt, splitter, tunnel entry, or tunnel exit tiles are selected, the panel's runtime group shows a **"Clear stuck items"** button that removes all items from the selected tiles. Clearing a tunnel entry or exit also discards all items currently in transit through that tunnel (REQ-BLD-TUNNEL-TRANSIT). This can be used to resolve stalled belts, splitters, and tunnels. The button acts on every selected tile, which is why a selection of belts and tunnel ends aggregates into one content rather than a count summary (REQ-UI-SELECTION-AGGREGATE).
+- REQ-UI-HQ-PANEL: When the HQ is selected, the panel shows the HQ's **HP** as a bar labelled `current / maximum` (REQ-HQ-STATS, REQ-UI-HP-BARS) and, beneath it, the **global building blocks stock** — the same value as the header bar's stock display (REQ-UI-BLOCKS-ICON), rendered as an item chip (REQ-UI-SINGLE-SELECTION) carrying the `building_block` icon on its colored square — a chip is an item display, so it takes the square even though the header bar's inline block icon does not (REQ-UI-ITEM-ICON, REQ-UI-BLOCKS-ICON), and hovering it shows the item production tooltip as any other chip does (REQ-UI-ITEM-TOOLTIP). The HP comes first, as it does on every card that has it (REQ-UI-SELECTION-CARD). The HQ has no input or output buffers of its own: building blocks delivered by belt go straight into the global stock (REQ-HQ-BELT-INPUT), and showing that stock on the HQ is what tells the player to route blocks there. The HQ has no configuration group and no status indicator (REQ-UI-SELECTION-STATUS), and it is never a construction site.
 - REQ-UI-ENTITY-CLICK-SELECT: The player can click any ship (player or enemy) or any defence station (player or enemy) in the game world to select it. A plain click on a ship or defence station makes it the sole selection, clearing any previous selection. Ships and defence stations can be multi-selected — by Ctrl+clicking individual actors to add or remove them, or by box-drag (REQ-UI-MULTI-SELECT) — and can be selected together with debris and with one another in a single field selection (REQ-UI-SELECTION-CATEGORIES), freely mixing player and enemy actors. Actors cannot be selected together with buildings: selecting a ship or defence station clears any building selection, and selecting a building clears the actors (buildings win). Clicking a piece of debris adds to or establishes a field selection (REQ-UI-DEBRIS-CLICK-SELECT). Clicking empty world space (no building, ship, defence station, or piece of debris) clears the selection.
-- REQ-UI-SHIP-STATS-PANEL: When exactly one ship is selected (REQ-UI-ENTITY-CLICK-SELECT) and no debris is selected, the selected building panel shows a **ship stats panel**. (If debris is also selected, the panel shows the compact count summary instead, per REQ-UI-FIELD-MULTI-SELECTION.) The panel structure mirrors REQ-MOD-UI-STATS-PANEL but reflects the ship's actual live state: stats are computed from its installed modules per REQ-MOD-STAT-CALC. The panel always shows all hull stats: HP (current / maximum), max linear speed, sensor range, main acceleration, maneuvering acceleration, angular acceleration, and max rotation speed. In addition, capability module summaries are shown conditioned on which module types are installed, using the same aggregation rules as REQ-MOD-UI-STATS-PANEL: weapons (combined DPS, maximum range), salvage (combined collection rate, maximum range), and repair (combined repair rate, maximum range), each section appearing only if at least one instance of that module type is installed. While debug draw mode is active (REQ-UI-DEBUG-DRAW), the panel additionally shows the ship's derived threat cost (REQ-MOD-THREAT).
-- REQ-UI-SHIP-BEHAVIOR: The ship stats panel (REQ-UI-SHIP-STATS-PANEL) additionally displays the selected ship's **current behavior** — a single label naming the top-priority behavior currently governing the ship's navigation, as resolved by the fixed-priority behavior arbitration. Only the winning behavior is named; lower-priority behaviors that are suppressed are not shown, and neither are the salvage/repair cycles that run regardless of the active behavior (REQ-SHP-SALVAGE, REQ-SHP-REPAIR). The label updates live as the ship's behavior changes, and it is always shown (independent of debug draw mode, unlike the threat-cost line of REQ-UI-SHIP-STATS-PANEL). This applies to both player and enemy ships (REQ-UI-ENTITY-CLICK-SELECT); enemy ships only ever show **Engaging** or **Advancing**. The behavior labels (all wrapped in `tr()`) are:
+- REQ-UI-SHIP-STATS-PANEL: When exactly one ship is selected (REQ-UI-ENTITY-CLICK-SELECT) and no debris is selected, the selection panel shows a **ship stats panel**. (If debris is also selected, the panel shows the compact count summary instead, per REQ-UI-FIELD-MULTI-SELECTION.) The panel structure mirrors REQ-MOD-UI-STATS-PANEL but reflects the ship's actual live state: stats are computed from its installed modules per REQ-MOD-STAT-CALC. Its header (REQ-UI-SELECTION-CARD) carries the schematic's color swatch and display name, with the ship's current behavior in the right slot (REQ-UI-SHIP-BEHAVIOR). The panel always shows all hull stats: HP (current / maximum) as a **bar** with the two values beside its caption, then max linear speed, sensor range, main acceleration, maneuvering acceleration, angular acceleration, and max rotation speed as label/value rows. In addition, capability module summaries are shown below the hull stats, each as its own outlined row, conditioned on which module types are installed and using the same aggregation rules as REQ-MOD-UI-STATS-PANEL: weapons (combined DPS, maximum range), salvage (combined collection rate, maximum range), and repair (combined repair rate, maximum range), each appearing only if at least one instance of that module type is installed. While debug draw mode is active (REQ-UI-DEBUG-DRAW), the panel additionally shows the ship's derived threat cost (REQ-MOD-THREAT).
+- REQ-UI-SHIP-BEHAVIOR: The ship stats panel (REQ-UI-SHIP-STATS-PANEL) additionally displays the selected ship's **current behavior** in its header's right slot (REQ-UI-SELECTION-CARD) — a single label naming the top-priority behavior currently governing the ship's navigation, as resolved by the fixed-priority behavior arbitration. Only the winning behavior is named; lower-priority behaviors that are suppressed are not shown, and neither are the salvage/repair cycles that run regardless of the active behavior (REQ-SHP-SALVAGE, REQ-SHP-REPAIR). The label updates live as the ship's behavior changes, and it is always shown (independent of debug draw mode, unlike the threat-cost line of REQ-UI-SHIP-STATS-PANEL). This applies to both player and enemy ships (REQ-UI-ENTITY-CLICK-SELECT); enemy ships only ever show **Engaging** or **Advancing**. The behavior labels (all wrapped in `tr()`) are:
   - **Retreating** — the ship is retreating (REQ-SHP-RETREAT).
   - **Engaging** — the ship is engaging a combat target (player: REQ-SHP-COMBAT; enemy: REQ-SHP-ENEMY-AI).
   - **Salvaging** — the ship is executing salvage navigation: seeking debris, collecting, or delivering to a Salvage Bay (REQ-SHP-SALVAGE).
@@ -543,27 +650,102 @@ The screen is divided into two columns: a main column (75% width) containing the
   - **Rallying** — the ship is moving to or orbiting the rally point (REQ-SHP-RALLY).
   - **Standby** — the ship is holding with its fleet (REQ-SHP-STANDBY).
   - **Advancing** — the ship is executing the baseline forward advance with no higher-priority behavior active (player: REQ-SHP-COMBAT advance toward the enemy; enemy: REQ-SHP-ENEMY-AI advance toward the asteroid).
-- REQ-UI-STATION-STATS-PANEL: When exactly one defence station is selected (REQ-UI-ENTITY-CLICK-SELECT) and no debris is selected, the selected building panel shows a **station stats panel** displaying the station's stats computed at its current level: HP (current / maximum), damage, range, and fire rate. (If debris is also selected, the panel shows the compact count summary instead, per REQ-UI-FIELD-MULTI-SELECTION.)
-- REQ-UI-FIELD-MULTI-SELECTION: A full single-object stats panel (REQ-UI-SHIP-STATS-PANEL, REQ-UI-STATION-STATS-PANEL, REQ-UI-DEBRIS-PANEL) is shown only when the field selection holds exactly one object — one ship, one defence station, or one piece of debris. Whenever the selection holds more than one field object — multiple actors, multiple pieces of debris, or any mix of actors and debris — the panel shows a **compact summary** instead: a count per type, one line per type rendered as "<type> x <count>" (the same `x`-count notation as the recipe tooltip and the building multi-selection, REQ-UI-MULTI-SELECTION). Ships are grouped by schematic display name and defence stations as a group, distinguishing player from enemy; all selected pieces of debris are grouped into a single "Debris x <count>" line whose count is the number of selected debris pieces. No per-object detail and no total-object-count header are shown (consistent with the building panel). If debris is part of the selection, a final "Scrap x <total>" line is appended after the "Debris" line, summing the remaining scrap across all selected debris (REQ-UI-DEBRIS-PANEL), so all lines share uniform spacing. Building selections use REQ-UI-SINGLE-SELECTION / REQ-UI-MULTI-SELECTION instead.
+- REQ-UI-STATION-STATS-PANEL: When exactly one defence station is selected (REQ-UI-ENTITY-CLICK-SELECT) and no debris is selected, the selection panel shows a **station stats panel** displaying the station's stats computed at its current level: HP (current / maximum) as a **bar** with the two values beside its caption, then damage, range, and fire rate as label/value rows, matching the ship stats panel's rendering (REQ-UI-SHIP-STATS-PANEL). Its header carries no right slot: a station has no behavior label and no status light. (If debris is also selected, the panel shows the compact count summary instead, per REQ-UI-FIELD-MULTI-SELECTION.)
+- REQ-UI-FIELD-MULTI-SELECTION: A full single-object stats panel (REQ-UI-SHIP-STATS-PANEL, REQ-UI-STATION-STATS-PANEL, REQ-UI-DEBRIS-PANEL) is shown when the field selection holds exactly one object — one ship, one defence station, or one piece of debris — and, for debris only, when it holds several pieces of debris and nothing else, which aggregate into that same content (REQ-UI-SELECTION-AGGREGATE). Every other field selection of more than one object — multiple actors, or any mix of actors and debris — shows a **count summary** instead. Its header reads `Mixed selection` with the total number of selected objects in the right slot (REQ-UI-SELECTION-CARD). Below it is one row per type — the type's symbol, its name, and the number selected as `x<count>`, the same `x`-count notation as the recipe tooltip and the building multi-selection (REQ-UI-MULTI-SELECTION). Ships are grouped by schematic display name and defence stations as a group, distinguishing player from enemy; all selected pieces of debris are grouped into a single `Debris` row whose count is the number of selected pieces. No per-object detail is shown. If debris is part of the selection, its row is followed by an indented sub-row giving the summed remaining scrap across all selected debris as the amount followed by the bare `scrap` icon, exactly as the debris panel states it (REQ-UI-DEBRIS-PANEL, REQ-UI-ITEM-ICON). Building selections use REQ-UI-SINGLE-SELECTION / REQ-UI-MULTI-SELECTION instead.
 - REQ-UI-DEBRIS-CLICK-SELECT: The player can click any piece of debris (REQ-RES-DEBRIS-DROP) in the game world to select it. Debris are field objects (REQ-UI-SELECTION-CATEGORIES) and can be selected together with ships and defence stations, but not with buildings. A plain click on a piece of debris makes it the sole selection, clearing any previous selection; selecting a building clears any debris (buildings win), and selecting a piece of debris clears any building selection. Hit-testing prefers a building over a coincident actor or piece of debris, and an actor (ship or defence station) over a coincident piece of debris: a piece of debris is selected only when no building or actor is under the cursor. A selected piece of debris that despawns or is fully collected (REQ-RES-DEBRIS-DROP) is removed from the selection; if no selected object remains, the panel becomes empty (REQ-UI-EMPTY-SELECTION).
 - REQ-UI-DEBRIS-MULTI-SELECT: Multiple pieces of debris can be selected by box-drag or by Ctrl+clicking individual pieces to add or remove them, mirroring building multi-select (REQ-UI-MULTI-SELECT). Debris shares the field-object category with ships and defence stations (REQ-UI-SELECTION-CATEGORIES), so a field selection may hold debris and actors together. Ctrl+clicking a piece of debris while a field selection is active adds or removes that piece within the same selection; Ctrl+clicking a piece of debris while a building selection is active first clears the buildings and begins a field selection (buildings win). Conversely, selecting a building while a field selection is active clears it. Box-drag disambiguation follows REQ-UI-MULTI-SELECT (a box covering any building selects buildings; a box covering no building selects the ships, defence stations, and debris within it).
-- REQ-UI-DEBRIS-PANEL: When exactly one piece of debris is selected (and no actors, REQ-UI-FIELD-MULTI-SELECTION), the selected building panel shows a **debris stats panel** structured like the ship and station stats panels (REQ-UI-SHIP-STATS-PANEL, REQ-UI-STATION-STATS-PANEL): a **"Debris"** heading followed by a single stat row, **"Scrap"**, showing that piece's current remaining scrap amount (REQ-RES-DEBRIS-DROP), rendered in the same label/value style as a ship hull stat row. When more than one field object is selected — multiple pieces of debris, or debris together with actors — the debris are instead summarized within the compact count summary (REQ-UI-FIELD-MULTI-SELECTION): a "Debris x <count>" line giving the number of selected debris pieces, followed by a "Scrap x <total>" line summing the remaining scrap across all selected debris. The displayed scrap value(s) update as selected debris are partially collected or despawn (REQ-UI-DEBRIS-CLICK-SELECT).
+- REQ-UI-DEBRIS-PANEL: When debris is selected and no actors are (REQ-UI-FIELD-MULTI-SELECTION), the selection panel shows a **debris stats panel** structured like the ship and station stats panels (REQ-UI-SHIP-STATS-PANEL, REQ-UI-STATION-STATS-PANEL): a header reading **"Debris"**, followed by a single stat row captioned **"Remaining"**, in the same label/value style as a ship hull stat row. Its value is the scrap amount followed by the `scrap` item icon drawn **bare, without its colored square** and sized to the row's text height — the same inline form the header bar uses for building blocks (REQ-UI-BLOCKS-ICON, REQ-UI-ITEM-ICON). The icon stands in for the word `Scrap`, which is why the caption names neither the item nor its unit; when no icon file exists for `scrap` (a missing icon is not an error, REQ-UI-ITEM-ICON), the row falls back to the caption `Scrap remaining` with the amount alone as its value. With one piece selected the row shows that piece's remaining scrap amount (REQ-RES-DEBRIS-DROP) and the header's right slot is empty. With several pieces selected the same content is shown aggregated (REQ-UI-SELECTION-AGGREGATE): the number of selected pieces appears in the header's right slot as `x<count>` and the row shows the summed remaining scrap across them. When debris is selected together with actors, the debris are instead summarized within the count summary (REQ-UI-FIELD-MULTI-SELECTION): a `Debris` row giving the number of selected pieces, followed by an indented sub-row with their summed remaining scrap, stated in the same amount-plus-bare-icon form. The displayed scrap value updates as selected debris are partially collected or despawn (REQ-UI-DEBRIS-CLICK-SELECT).
 
 ### Build Button Bar
 
 - REQ-UI-BUILD-BAR: All placeable building types are shown as a **single horizontal row** of buttons with no grouping and no wrapping, inside a widget that **floats over the game world view** (REQ-UI-WORLD-SIZE), horizontally centered and anchored at the bottom edge with a small margin. Tunnel Entry and Tunnel Exit share a single **Tunnel** button (REQ-BLD-TUNNEL-MODE) rather than one button each. The bar is sized to its buttons and re-centers whenever the set of shown buttons changes (REQ-LOCK-BUILDING) or the view is resized.
   - **Overlay behavior.** The bar occludes the strip of the game world it covers; the world view itself keeps its full extent and the view's scrolling, ghost rendering, and tile geometry are unaffected (the world is not inset for the bar). The bar is drawn above the pause and deconstruct vignettes (REQ-UI-PAUSE-BORDER, REQ-UI-DECONSTRUCT-BORDER), which keep their full 100-pixel bottom band underneath it, and below the modal dim (REQ-UI-MODAL-DIM), which covers the entire game window including the bar.
+  - **No overlap with the selection panel.** The bar and the selection panel (REQ-UI-SELECTION-PANEL) never overlap, and keeping them apart is entirely the panel's job: the bar's position depends only on its own button set and the view size, and it never moves, re-centers, or resizes because the panel appears, disappears, or changes size. The panel instead steps around the bar's current rectangle wherever its own column would meet it (REQ-UI-SELECTION-PANEL).
   - **Input.** Mouse events over the bar are consumed by the bar and never reach the game world: hovering it shows no builder-mode ghost at the tile beneath, and clicking it neither places a building nor changes the selection. Right-clicking the bar does not exit builder mode (REQ-BLD-BUILDER-MODE) or cancel a belt drag (REQ-BLD-BELT-DRAG).
 - REQ-UI-BUILD-COST: Each button is **icon-only with a cost**, its face composed of three elements: the button's **hotkey badge** in the top-left corner, the building's icon (REQ-UI-BUILD-ICON) centered below it, and the building block cost centered under the icon, shown with the `building_block` item icon (REQ-UI-BLOCKS-ICON, REQ-UI-ITEM-ICON) to the right of the number in place of the trailing `Blocks` word, e.g. `2` then a small block icon. The building name is not shown on the button; it is shown in the button's hover tooltip instead (REQ-UI-BUILD-TOOLTIP). When no icon file exists for `building_block`, the cost is shown as the bare number. The Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON) has no cost and shows its name as a text caption in the cost's place.
   - **Hotkey badge.** The badge names the build hotkey that activates the button (REQ-UI-HOTKEYS), so the player can learn the shortcuts from the bar itself. It is rendered dimmer than the cost so it reads as secondary, but at the same size and in bold, because a smaller badge is not legible. A plain-digit hotkey is shown as the bare digit (`1`, `2`, `3`); a Shift+digit hotkey is shown with an upwards arrow prefixed and no separator (`↑1` … `↑6`); the Deconstruct button shows `Q`. A button whose building type has no build hotkey shows no badge and keeps the same face size, so the row stays even.
 - REQ-UI-BUILD-ICON: Each build button shows an icon. Icons are SVG files loaded at runtime from `data/icons/buildings/` (a sibling of the config directory, read the same way as `visuals.toml`), one file per button named after the building's id (e.g. `belt.svg`, `reprocessing_plant.svg`). The shared Tunnel button (REQ-UI-BUILD-BAR) uses `tunnel_entry.svg`; the Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON) uses `deconstruct.svg`. Each icon is a rounded colored "chip" bearing a white line glyph, the chip color following the building's fill color in `visuals.toml`. A missing icon file leaves the button showing its building name as a text caption in place of the icon, so the button stays identifiable in the icon-only bar (REQ-UI-BUILD-COST); it is not an error.
-- REQ-UI-BUILD-TOOLTIP: Each building-type button shows a hover tooltip consisting of the building name followed by the descriptive text defined for that building type in `buildings.toml` (the optional per-building tooltip field). Because the button caption is icon-only (REQ-UI-BUILD-COST), the name is always part of the tooltip; if a building type defines no tooltip text, the tooltip shows the name alone. This tooltip is distinct from the recipe/schematic selection tooltip (REQ-UI-SELECT-TOOLTIP). The Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON) is not a building type and so has no config-defined tooltip; it instead shows its own refund tooltip defined in REQ-UI-DECONSTRUCT-BUTTON.
+- REQ-UI-BUILD-TOOLTIP: Each building-type button shows a hover tooltip consisting of the building name followed by the descriptive text defined for that building type in `buildings.toml` (the optional per-building tooltip field). Because the button caption is icon-only (REQ-UI-BUILD-COST), the name is always part of the tooltip; if a building type defines no tooltip text, the tooltip shows the name alone. This tooltip is distinct from the item production tooltip of the selection panel's item chips (REQ-UI-ITEM-TOOLTIP); the recipe/schematic selection dialog has no tooltip at all (REQ-UI-SELECT-OPTIONS). The Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON) is not a building type and so has no config-defined tooltip; it instead shows its own refund tooltip defined in REQ-UI-DECONSTRUCT-BUTTON.
 - REQ-UI-BUILD-DISABLED: Buttons for buildings the player cannot currently afford are shown as disabled. A disabled button's icon (REQ-UI-BUILD-ICON) is rendered in a greyed variant, with its colored chip background recolored grey while the white glyph is retained.
-- REQ-UI-DECONSTRUCT-BUTTON: A dedicated **Deconstruct** button is shown in the build button bar (REQ-UI-BUILD-BAR), as the last entry of the row and **visually separated** from the building-type buttons by a gap (not a divider line), because it toggles a mode rather than selecting a building type. Its face follows REQ-UI-BUILD-COST with two differences: its hotkey badge reads `Q`, and because it has no building block cost it shows its **Deconstruct** name as a text caption where the building-type buttons show their cost — so it is the one labelled button in the bar. It is therefore wider than the building-type buttons, which share a uniform width. Clicking it toggles deconstruct mode on and off, equivalent to the Q deconstruct toggle (REQ-UI-HOTKEYS). The button is shown in a visually active/pressed state while deconstruct mode is active. The button shows a hover tooltip stating the deconstruction refund (REQ-BLD-DECONSTRUCT): that deconstructing a fully-built building returns `world.toml [world].refund_percentage` percent of its building block cost once deconstruction completes, and that a construction site removed before it finishes building is refunded in full. When `refund_percentage` is 100% both cases yield the same refund, and the tooltip is simplified to state the single refund percentage without distinguishing the two cases. Unlike the building-type button tooltips (REQ-UI-BUILD-TOOLTIP), this tooltip is not config-defined text but is composed from the refund percentage.
+- REQ-UI-DECONSTRUCT-BUTTON: A dedicated **Deconstruct** button is shown in the build button bar (REQ-UI-BUILD-BAR), as the last entry of the row and **visually separated** from the building-type buttons by a gap (not a divider line), because it toggles a mode rather than selecting a building type. Its face follows REQ-UI-BUILD-COST with two differences: its hotkey badge reads `Q`, and because it has no building block cost it shows its **Deconstruct** name as a text caption where the building-type buttons show their cost — so it is the one labelled button in the bar. It is therefore wider than the building-type buttons, which share a uniform width. Clicking it toggles deconstruct mode on and off; entering the mode clears the selection (REQ-UI-SELECTION-EXCLUSIVE), which is the one way in which it differs from the Q key (REQ-UI-HOTKEYS): Q clears a selection before it enters the mode, so with something selected the button gets there in one click and Q in two. The button is shown in a visually active/pressed state while deconstruct mode is active. The button shows a hover tooltip stating the deconstruction refund (REQ-BLD-DECONSTRUCT): that deconstructing a fully-built building returns `world.toml [world].refund_percentage` percent of its building block cost once deconstruction completes, and that a construction site removed before it finishes building is refunded in full. When `refund_percentage` is 100% both cases yield the same refund, and the tooltip is simplified to state the single refund percentage without distinguishing the two cases. Unlike the building-type button tooltips (REQ-UI-BUILD-TOOLTIP), this tooltip is not config-defined text but is composed from the refund percentage.
+
+### Controls Panel
+
+The controls panel tells the player which controls are available right now. It is context-sensitive: the game is always in exactly one **control context**, derived from the active build mode and the current selection, and the panel shows that context's rows and no others. Its position, size, and overlay behavior are defined in REQ-UI-CONTROLS-PANEL; its structure in REQ-UI-CONTROLS-CARD; and which rows each context shows in REQ-UI-CONTROLS-CONTENT. The panel never defines a binding: every row restates one already defined in REQ-UI-HOTKEYS or in the mouse gestures cited beside it.
+
+- REQ-UI-CONTROLS-PANEL: The **controls panel** is a widget that **floats over the game world view** (REQ-UI-WORLD-SIZE), anchored to the view's **bottom-left corner** with a small margin on both edges. It is **sized to its content in both width and height**, growing and shrinking upward from that corner as the context changes. Should its content ever be taller than the view, the panel's height is capped at the view height less its margins and the content scrolls vertically within it. The selection panel is placed beside the current selection (REQ-UI-SELECTION-PANEL) and so can reach this corner; the two never overlap, and keeping them apart is entirely the selection panel's job — this panel's position depends only on its own content, the view size, and the build button bar, and it never moves or resizes because the selection panel appears, disappears, or changes size.
+  - **Stepping around the build button bar.** Like the selection panel (REQ-UI-SELECTION-PANEL), the panel does **not** confine itself to the band above the build button bar's strip: the bar is horizontally centered and sized to its buttons (REQ-UI-BUILD-BAR), so it normally leaves this corner free, and the panel shares the view's bottom edge with it. The panel **rises only to avoid an actual overlap**: whenever the panel at the bottom-left corner would intersect the bar's current rectangle, it is moved up so that its bottom edge clears the bar's top by the same margin it keeps from the view's edges, and its height is capped at the space that leaves. Whether it rises therefore depends on how wide the bar and the panel currently are, and it returns to the corner as soon as they no longer meet. The bar never moves on the panel's account (REQ-UI-BUILD-BAR).
+  - **Visibility.** The panel is shown whenever the game is being played. Unlike the selection panel it has no empty state (REQ-UI-EMPTY-SELECTION): every context has rows, so there is never nothing to show.
+  - **Collapsing.** Clicking anywhere on the panel's header (REQ-UI-CONTROLS-CARD) toggles the panel between **expanded** and **collapsed**. Collapsed, it shows its header alone, keeping the context name visible and the header clickable so the panel can be expanded again; expanded, it shows the header followed by every row of the current context. The panel starts **expanded**. Changing context does not change the collapsed state: a panel collapsed in one context stays collapsed in the next, and its header updates in place. The collapsed state is presentation-only — it is not a player command, never enters the replay stream, and has no effect on the simulation. It persists for as long as the application runs, including across a restart from the escape menu (REQ-UI-GAME-MENU), and is not saved to disk.
+  - **Overlay behavior.** As for the build button bar and the selection panel (REQ-UI-BUILD-BAR, REQ-UI-SELECTION-PANEL): the panel occludes the strip of the game world it covers; the world view itself keeps its full extent and the view's scrolling, ghost rendering, and tile geometry are unaffected. It is drawn above the pause and deconstruct vignettes (REQ-UI-PAUSE-BORDER, REQ-UI-DECONSTRUCT-BORDER), which keep their full left-hand band underneath it, and below the modal dim (REQ-UI-MODAL-DIM), which covers the entire game window including the panel.
+  - **Input.** Mouse events over the panel are consumed by the panel and never reach the game world: hovering it shows no builder-mode ghost at the tile beneath, and clicking it neither places a building nor changes the selection. Right-clicking the panel does not exit builder mode (REQ-BLD-BUILDER-MODE) or cancel a belt drag (REQ-BLD-BELT-DRAG). The only control the panel itself offers is the header click that collapses and expands it.
+- REQ-UI-CONTROLS-CARD: **Card structure.** The panel is a card with two parts, top to bottom:
+  - **Header** — always shown, and the panel's only interactive element (REQ-UI-CONTROLS-PANEL). It holds a colored context dot on the left, the context's name beside it in upper case, and, for contexts that define one, a **detail suffix** separated by a middle dot (`BUILD MODE · Assembler`). The name and detail per context are given in REQ-UI-CONTROLS-CONTENT.
+  - **Rows** — one per available control, shown only while the panel is expanded. Each row is one or more **key badges** on the left — the key or mouse button drawn as a small bordered chip — and a **label** beside them naming what it does. An action reachable two ways carries both badges in the same row (`RMB` `Q` — Exit placement) rather than occupying two rows. A row whose action hands the current context back — leaving a build mode, or clearing the selection (REQ-UI-SELECTION-EXCLUSIVE) — is drawn with the destructive badge styling, distinguishing it from the rows that act within the context; to the player both are the one key that backs out, so both are marked alike. No row is ever drawn greyed or otherwise disabled: a control the player cannot currently use is not shown at all (REQ-UI-CONTROLS-ACCURACY).
+
+  The rows that are live in every context (REQ-UI-CONTROLS-CONTENT) are shown last, under a divider and the caption `ALWAYS AVAILABLE`. This holds in every context including the General one, which has context rows of its own above the divider like any other, so the card is read the same way wherever the player is.
+- REQ-UI-CONTROLS-CONTENT: **Content catalog.** The control context follows from the active build mode and the selection alone. Build modes are mutually exclusive (REQ-BLD-BUILDER-MODE), so exactly one context applies at any moment:
+
+  | Context | When | Header name | Header detail |
+  |---|---|---|---|
+  | General | no build mode active, nothing selected | `GENERAL` | — |
+  | Selection | no build mode active, at least one object selected | `SELECTION` | `<n> buildings` or `<n> objects` |
+  | Build | builder mode active (REQ-BLD-BUILDER-MODE) | `BUILD MODE` | the name of the building type that would be placed at the hovered position, so in tunnel mode it follows the resolved end and reads `Tunnel Entry` or `Tunnel Exit` (REQ-BLD-TUNNEL-MODE) |
+  | Blueprint | blueprint placement mode active (REQ-UI-BLUEPRINT-MODE) | `BLUEPRINT MODE` | the blueprint's name, or `Temporary` for a temporary blueprint (REQ-UI-BLUEPRINT-TEMP) |
+  | Deconstruct | deconstruct mode active (REQ-UI-DECONSTRUCT-BUTTON) | `DECONSTRUCT MODE` | — |
+
+  The Selection context's detail counts the selection and names its category (REQ-UI-SELECTION-CATEGORIES): `<n> buildings` for a building selection, `<n> objects` for a field selection, in the singular at a count of one. The Build and Blueprint contexts show **the same rows** and differ only in their header.
+
+  **The row that hands the context back is last.** Where a context has one — `Q` — Clear selection in the Selection context, `RMB` `Q` — Exit placement in Build and Blueprint, `RMB` `Q` — Exit deconstruct mode in Deconstruct — it is the final context row, below the rows that act within the context, and it carries the destructive badge styling (REQ-UI-CONTROLS-CARD). The General context has none: with no mode to leave and nothing selected, its `Q` row enters deconstruct mode rather than leaving anything, and is an ordinary row that happens to come last.
+
+  **Always-available rows**, shown in every context:
+
+  | Badges | Label | Shown |
+  |---|---|---|
+  | `A` `D` | Move | always |
+  | `W` `S` | Game speed | always |
+  | `Space` | Toggle pause | always |
+  | `V` | Paste last | only while a temporary blueprint exists (REQ-UI-BLUEPRINT-TEMP) |
+  | `Ctrl` `V` | Blueprints | always |
+  | `Esc` | Menu | always |
+
+  **Context rows**, shown above the always-available block:
+
+  | Context | Badges | Label |
+  |---|---|---|
+  | General | `LMB` | Select |
+  | | `LMB` drag | Select area |
+  | | `Q` | Deconstruct mode |
+  | Selection | `LMB` | Select / clear selection |
+  | | `LMB` drag | Select area |
+  | | `Ctrl` `LMB` | Add / remove from selection |
+  | | `Ctrl` `LMB` drag | Add area to selection |
+  | | `C` | Copy to temporary blueprint |
+  | | `Ctrl` `C` | Create blueprint |
+  | | `Q` | Clear selection |
+  | Build, Blueprint | `LMB` | Place |
+  | | `LMB` drag | Place belt line |
+  | | `R` / `Shift` `R` | Rotate |
+  | | `RMB` `Q` | Exit placement |
+  | Deconstruct | `LMB` | Toggle deconstruct |
+  | | `LMB` drag | Deconstruct area |
+  | | `RMB` `Q` | Exit deconstruct mode |
+
+  Four rows are conditional on more than the context, because the binding behind them is:
+  - **`C` / `Ctrl` `C`** are shown only while the selection holds at least one player-placeable building, the condition under which those keys do anything (REQ-UI-HOTKEYS). A selection of ships, defence stations, or debris shows neither.
+  - **`LMB` drag — Place belt line** is shown only in builder mode for the Belt type, the only type placed by dragging (REQ-BLD-BELT-DRAG). Every other builder type and blueprint placement omit the row.
+  - **`RMB` `Q` — Exit placement** splits into two rows **while a belt drag is in progress**, because the two bindings then part company (REQ-BLD-BELT-DRAG): `RMB` reads **Cancel belt line** and cancels the drag while leaving builder mode active, and `Q` reads **Exit placement** and leaves the mode outright.
+  - **`LMB` — Place** reads **Apply settings** instead whenever the ghost under the cursor resolves to a configuration transfer (REQ-UI-BLUEPRINT-TRANSFER) — a single-building blueprint hovering a same-type building of a configurable type, which is the case in which clicking hands over settings rather than placing anything. A blueprint holding more than one building keeps the `Place` label, since its click both places and transfers (REQ-UI-BLUEPRINT-PLACE).
+- REQ-UI-CONTROLS-ACCURACY: **The panel never advertises a binding that would do nothing.** Every row shown must, if triggered in the situation the panel is showing it in, have the effect its label names; a binding that is inert in the current context is omitted rather than shown greyed (REQ-UI-CONTROLS-CARD). The relation holds in one direction only: the panel may omit a binding that is available, and deliberately does so in three cases:
+  - **Build hotkeys** (REQ-UI-HOTKEYS) are live in every context, but are advertised on the build buttons' badges (REQ-UI-BUILD-COST) instead of taking eleven rows in every context of this panel.
+  - **`Ctrl` `LMB` and `Ctrl` `LMB` drag** work with nothing selected — they select the object under the cursor much as a plain click would — but are shown only in the Selection context. "Add / remove from selection" names an operation on a selection, and there is none to operate on until something is selected; the plain `LMB` row already covers what the gesture does before then.
+  - **`F3` and `F4`** (REQ-UI-DEBUG-DRAW) are development controls rather than player controls and appear in no context.
+
+  This asymmetry between what is available and what is shown is why the two are separate questions in the implementation, and why the tests assert that a resolvable input is *available* rather than that it is displayed.
 
 ### Blueprints
 
-Blueprints occupy no permanent screen space. They are saved with **Ctrl+C** from the current selection (REQ-UI-BLUEPRINT-CREATE) and picked for placement from the blueprint selection dialog, opened with **Ctrl+V** (REQ-UI-BLUEPRINT-DIALOG). The unmodified **C** and **V** keys are the throwaway counterparts of the same two gestures: they capture and re-place a single unnamed temporary blueprint that is never saved and never listed (REQ-UI-BLUEPRINT-TEMP). There is no blueprint panel in the side panel column (REQ-UI-PANEL-COLUMN). (The ship layout blueprint panel of the layout configuration dialog, REQ-MOD-UI-BLUEPRINT-PANEL, is a separate feature and is unaffected.)
+Blueprints occupy no permanent screen space. They are saved with **Ctrl+C** from the current selection (REQ-UI-BLUEPRINT-CREATE) and picked for placement from the blueprint selection dialog, opened with **Ctrl+V** (REQ-UI-BLUEPRINT-DIALOG). The unmodified **C** and **V** keys are the throwaway counterparts of the same two gestures: they capture and re-place a single unnamed temporary blueprint that is never saved and never listed (REQ-UI-BLUEPRINT-TEMP). Blueprints have no widget on the game screen at all. (The ship layout blueprint panel of the layout configuration dialog, REQ-MOD-UI-BLUEPRINT-PANEL, is a separate feature and is unaffected.)
 
 - REQ-UI-BLUEPRINT-CREATE: Pressing **Ctrl+C** (REQ-UI-HOTKEYS) opens the modal **blueprint save dialog**, which pauses the simulation and dims the game window (REQ-UI-MODAL-DIM). It has effect only when at least one player-placeable building (i.e. a building with a button in the build button bar) is currently selected; non-player-placeable buildings (HQ, defence stations) in the selection do not count toward this condition, and pressing Ctrl+C with an empty selection or a selection of only non-player-placeable buildings does nothing (no dialog opens). A selected player-placeable building may be either an operational building or a construction site (a building placed but not yet fully built, REQ-BLD-SITE-CONFIG); both count toward this condition and are captured identically (REQ-UI-BLUEPRINT-STORAGE). The dialog prompts the player to enter a name and has Confirm and Cancel buttons. Clicking Cancel — or pressing Escape, or closing the dialog — closes it with no effect and does not open the blueprint selection dialog. Clicking Confirm with a non-empty name creates a blueprint from the current selection, silently excluding any non-player-placeable buildings, appends it to the blueprint list, closes the save dialog, and immediately opens the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG) showing the new blueprint among the others.
 
@@ -572,7 +754,7 @@ Blueprints occupy no permanent screen space. They are saved with **Ctrl+C** from
   - Below it, a **scrollable two-column grid of blueprint cards** (REQ-UI-BLUEPRINT-CARD), one per saved blueprint, filling the grid left to right and top to bottom in creation order. The column count is fixed at two; the grid scrolls vertically when the cards do not fit, and does not scroll horizontally.
   - When no blueprints are saved, the dialog still opens and shows an empty-state message in place of the grid, telling the player that blueprints are created with Ctrl+C from a selection of buildings.
 
-  Clicking the close button, pressing Escape, or closing the dialog through the window manager closes it with no other effect: the current selection, build mode, and blueprint list are unchanged, and the simulation speed is restored to what it was before the dialog was opened. While the dialog is open, Escape closes it rather than opening the escape menu (REQ-UI-GAME-MENU).
+  Clicking the close button, pressing Escape, pressing Q (REQ-UI-DIALOG-DISMISS), or closing the dialog through the window manager closes it with no other effect: the current selection, build mode, and blueprint list are unchanged, and the simulation speed is restored to what it was before the dialog was opened. While the dialog is open, Escape closes it rather than opening the escape menu (REQ-UI-GAME-MENU), and Q closes it rather than acting on the game world beneath.
 
 ```
 +------------------------------------------------------+
@@ -588,7 +770,7 @@ Blueprints occupy no permanent screen space. They are saved with **Ctrl+C** from
 +------------------------------------------------------+
 ```
 
-- REQ-UI-BLUEPRINT-TEMP: Pressing the **C** key (REQ-UI-HOTKEYS) creates a **temporary blueprint** from the current selection and immediately enters blueprint placement mode for it, without opening the naming dialog. It has effect only when at least one player-placeable building is currently selected — the same condition as REQ-UI-BLUEPRINT-CREATE; pressing C with an empty selection, or a selection containing only non-player-placeable buildings (HQ, defence stations), does nothing at all, and in particular leaves any existing temporary blueprint in place. Entering this mode replaces any currently active build, blueprint placement, or deconstruct mode. The temporary blueprint is captured exactly as a saved blueprint (REQ-UI-BLUEPRINT-STORAGE), silently excluding any non-player-placeable buildings from the selection, but it is never named, never shown in the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG), and never persisted to `blueprints.toml` (REQ-UI-BLUEPRINT-SAVE). Placement behaves identically to a saved blueprint's placement mode (REQ-UI-BLUEPRINT-MODE, REQ-UI-BLUEPRINT-PLACE): a ghost is rendered per building, R / Shift+R rotate the entire constellation, placement follows the same per-building validity and total-cost rules, and after a successful placement the mode stays active so the blueprint can be placed again. Right-clicking in the game world exits placement mode; unlike the mode, the temporary blueprint itself survives, so it can be entered again with V.
+- REQ-UI-BLUEPRINT-TEMP: Pressing the **C** key (REQ-UI-HOTKEYS) creates a **temporary blueprint** from the current selection and immediately enters blueprint placement mode for it, without opening the naming dialog. It has effect only when at least one player-placeable building is currently selected — the same condition as REQ-UI-BLUEPRINT-CREATE; pressing C with an empty selection, or a selection containing only non-player-placeable buildings (HQ, defence stations), does nothing at all, and in particular leaves any existing temporary blueprint in place. Entering this mode replaces any currently active build, blueprint placement, or deconstruct mode, and clears the selection — the blueprint is captured from it first, so C loses nothing (REQ-UI-SELECTION-EXCLUSIVE). The temporary blueprint is captured exactly as a saved blueprint (REQ-UI-BLUEPRINT-STORAGE), silently excluding any non-player-placeable buildings from the selection, but it is never named, never shown in the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG), and never persisted to `blueprints.toml` (REQ-UI-BLUEPRINT-SAVE). Placement behaves identically to a saved blueprint's placement mode (REQ-UI-BLUEPRINT-MODE, REQ-UI-BLUEPRINT-PLACE): a ghost is rendered per building, R / Shift+R rotate the entire constellation, placement follows the same per-building validity and total-cost rules, and after a successful placement the mode stays active so the blueprint can be placed again. Right-clicking in the game world exits placement mode; unlike the mode, the temporary blueprint itself survives, so it can be entered again with V.
 
   Pressing the **V** key re-enters blueprint placement mode for the temporary blueprint, capturing nothing new: it is independent of the current selection, can be pressed any number of times, and yields exactly the mode described above. Like C it replaces any currently active build, blueprint placement, or deconstruct mode, and it does not test whether the player can currently afford the blueprint — cost is enforced at placement (REQ-UI-BLUEPRINT-PLACE), consistently with C. Pressing V when no temporary blueprint exists does nothing: no mode is entered and any currently active mode is left untouched.
 
@@ -634,7 +816,7 @@ Blueprints occupy no permanent screen space. They are saved with **Ctrl+C** from
   - The ghost is drawn in a distinct **transfer** color read from `visuals.toml [overlays]`, overriding both the per-building coloring and the "invalid" color (REQ-BLD-GHOST, REQ-BLD-PLACE-VALID). The position counts as valid despite the occupied tiles (REQ-BLD-PLACE-VALID condition (b)).
   - **Left-clicking transfers the configuration** to the existing building or site, making the target's settings **identical to the source's**: the recipe ID (Miner, Assembler), the schematic ID together with the ship layout (Shipyard), or the two output filters (Splitter). No construction site is placed, no building blocks are consumed (it is excluded from the total cost of REQ-UI-BLUEPRINT-PLACE), and the target's **rotation is not changed** — a transfer never rotates.
   - The transfer is a **full mirror, including the absence of a setting**: where the blueprint stores no configuration for a field (REQ-UI-BLUEPRINT-STORAGE stores nothing for an unselected recipe or schematic, and no filter lists for a splitter whose filters were empty at capture time), the target's corresponding setting is **cleared** rather than left as it was. So a splitter captured with no filters clears the target splitter's filters back to accept-all, and a miner captured with no recipe selected clears the target miner's recipe. This holds for every blueprint size, so a constellation captured from unconfigured buildings clears the settings of every matching building it is dropped on.
-  - The transfer has the same effects as making that selection through the selected building panel, clearing included: buffer clearing per REQ-MAT-INPUT-BUFFER and REQ-MAT-OUTPUT-BUFFER, and, for a Shipyard, in-progress cycle cancellation per REQ-BLD-SHIPYARD. It inherits the no-op rule of REQ-MAT-INPUT-BUFFER with them: a transfer onto a building whose settings already match the source changes nothing at all — no buffers cleared, no production cycle cancelled, no construction progress lost — so repeatedly clicking already-matching buildings is harmless. Each field is judged on its own, so transferring an identical recipe with a differing layout affects only the layout. The layout configuration dialog does not auto-open (REQ-MOD-UI-AUTO-DIALOG).
+  - The transfer has the same effects as making that selection through the selection panel, clearing included: buffer clearing per REQ-MAT-INPUT-BUFFER and REQ-MAT-OUTPUT-BUFFER, and, for a Shipyard, in-progress cycle cancellation per REQ-BLD-SHIPYARD. It inherits the no-op rule of REQ-MAT-INPUT-BUFFER with them: a transfer onto a building whose settings already match the source changes nothing at all — no buffers cleared, no production cycle cancelled, no construction progress lost — so repeatedly clicking already-matching buildings is harmless. Each field is judged on its own, so transferring an identical recipe with a differing layout affects only the layout. The layout configuration dialog does not auto-open (REQ-MOD-UI-AUTO-DIALOG).
   - Unlock gating matches placement (REQ-UI-BLUEPRINT-PLACE): a stored schematic is applied only if it is currently unlocked, and locked recipe IDs and splitter filter entries for locked item types are handled per REQ-LOCK-UI-BLUEPRINT.
   - Both operational buildings and construction sites are transfer targets (REQ-BLD-SITE-CONFIG); a configuration applied to a site carries over unchanged when it finishes building.
   - After the transfer the game stays in blueprint placement mode, so further same-type buildings can be clicked in turn.

src/CMakeLists.txt

@@ -10,7 +10,12 @@ set(TARGET_LIB_INCLUDE_DIRS
     "${CMAKE_CURRENT_SOURCE_DIR}/lib"
     "${CMAKE_CURRENT_SOURCE_DIR}/external"
 )
-set(TARGET_UI_INCLUDE_DIRS "${CMAKE_CURRENT_SOURCE_DIR}/ui")
+set(TARGET_UI_INCLUDE_DIRS
+    "${CMAKE_CURRENT_SOURCE_DIR}/ui"
+    # The balancing target compiles a few ui files into itself rather than linking the
+    # ui library, and the ship stats panel is built from the selection card's parts.
+    "${CMAKE_CURRENT_SOURCE_DIR}/ui/selection"
+)
 set(TARGET_TEST_INCLUDE_DIRS "${CMAKE_CURRENT_SOURCE_DIR}/test")
 set(TARGET_BALANCING_INCLUDE_DIRS "${CMAKE_CURRENT_SOURCE_DIR}/balancing")
 
@@ -78,6 +83,7 @@ unset(SRCS)
 
 set(HDRS)
 set(SRCS)
+set(UI_INCLUDE_PATH)
 
 add_subdirectory(ui)
 
@@ -106,6 +112,7 @@ set_target_properties(${TARGET_UI_NAME} PROPERTIES
 )
 target_include_directories(${TARGET_UI_NAME} PUBLIC
     "${TARGET_UI_INCLUDE_DIRS}"
+    "${UI_INCLUDE_PATH}"
     "${TARGET_LIB_INCLUDE_DIRS}"
     "${LIB_INCLUDE_PATH}"
 )

src/balancing/CMakeLists.txt

@@ -7,6 +7,15 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/BalancingWindow.h
 	${CMAKE_CURRENT_SOURCE_DIR}/InspectWindow.h
 	${CMAKE_CURRENT_SOURCE_DIR}/../ui/ShipStatsPanel.h
+	# The card parts the ship stats panel is built from. They are deliberately free of
+	# Simulation and GameConfig, which is what lets them come along here.
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/selection/StatRow.h
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/selection/BarRow.h
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/selection/SectionBox.h
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/selection/SelectionNames.h
+	# A stat row states a value with an inline item icon (REQ-UI-ITEM-ICON), which this
+	# composes; it needs nothing but Qt's painting.
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/IconCaption.h
 	${CMAKE_CURRENT_SOURCE_DIR}/../ui/VisualsConfig.h
 	${CMAKE_CURRENT_SOURCE_DIR}/../ui/VisualsLoader.h
 	# Shared world-space shapes so the arena keeps looking like the game
@@ -26,6 +35,11 @@ SET(SRCS
 	${CMAKE_CURRENT_SOURCE_DIR}/BalancingWindow.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/InspectWindow.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/../ui/ShipStatsPanel.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/selection/StatRow.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/selection/BarRow.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/selection/SectionBox.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/selection/SelectionNames.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/../ui/IconCaption.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/../ui/VisualsLoader.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/../ui/WorldPrimitives.cpp
 	PARENT_SCOPE

src/lib/config/ConfigLoaderRecipes.cpp

@@ -32,15 +32,46 @@ std::vector<RecipeOutput> parseRecipeOutputs(const toml::array& arr,
         RecipeOutput out;
         out.item = utility::requireString(mt["item"], file, elemPath + ".item");
         out.amount = static_cast<int>(utility::requireInt(mt["amount"], file, elemPath + ".amount"));
+        result.push_back(std::move(out));
+    }
+    return result;
+}
+
+// The several-group form: one [[recipe.output_group]] entry per possible result, each
+// carrying its weight and the items it yields together (REQ-MAT-OUTPUT-GROUP).
+std::vector<RecipeOutputGroup> parseOutputGroups(const toml::array& arr,
+                                                 const std::string& file,
+                                                 const std::string& path)
+{
+    std::vector<RecipeOutputGroup> result;
+    result.reserve(arr.size());
+    for (std::size_t i = 0; i < arr.size(); ++i)
+    {
+        const std::string elemPath = path + "[" + std::to_string(i) + "]";
+        const toml::table* t = arr[i].as_table();
+        if (t == nullptr)
+        {
+            throw utility::makeError(file, elemPath, "not a table");
+        }
+        toml::table& mt = const_cast<toml::table&>(*t);
+
+        RecipeOutputGroup group;
+        const toml::array& items =
+            utility::requireArray(mt["items"], file, elemPath + ".items");
+        group.items = parseRecipeOutputs(items, file, elemPath + ".items");
+        if (group.items.empty())
+        {
+            throw utility::makeError(file, elemPath + ".items", "produces nothing");
+        }
         if (const std::optional<double> p = mt["probability"].value<double>())
         {
-            out.probability = *p;
+            group.probability = *p;
         }
         else if (const std::optional<int64_t> p = mt["probability"].value<int64_t>())
         {
-            out.probability = static_cast<double>(*p);
+            group.probability = static_cast<double>(*p);
         }
-        result.push_back(std::move(out));
+        result.push_back(std::move(group));
     }
     return result;
 }
@@ -91,15 +122,33 @@ RecipesConfig ConfigLoader::loadRecipes(const std::string& path)
             def.inputs = utility::parseIngredients(inputs, file, elemPath + ".inputs");
         }
 
-        const toml::array& outputs = utility::requireArray(mt["outputs"], file, elemPath + ".outputs");
-        def.outputs = parseRecipeOutputs(outputs, file, elemPath + ".outputs");
-
-        // Optional icon item id (REQ-UI-RECIPE-ICON); defaults to the first output
-        // in the UI when unset. Not validated against known items here — a missing
-        // icon is not an error (REQ-UI-ITEM-ICON).
-        if (mt.contains("icon"))
+        // Either form, never both (REQ-MAT-OUTPUT-GROUP): `outputs` is the single-group
+        // shorthand that all but the reprocessing recipes use, `output_group` the several-
+        // group form. The shorthand carries no weight -- with one group nothing is picked.
+        const bool hasOutputs = mt.contains("outputs");
+        const bool hasGroups  = mt.contains("output_group");
+        if (hasOutputs && hasGroups)
         {
-            def.icon = utility::requireString(mt["icon"], file, elemPath + ".icon");
+            throw utility::makeError(file, elemPath,
+                "has both 'outputs' and 'output_group'; use one or the other");
+        }
+        if (hasGroups)
+        {
+            const toml::array& groups =
+                utility::requireArray(mt["output_group"], file, elemPath + ".output_group");
+            def.outputGroups = parseOutputGroups(groups, file, elemPath + ".output_group");
+            if (def.outputGroups.empty())
+            {
+                throw utility::makeError(file, elemPath + ".output_group", "is empty");
+            }
+        }
+        else
+        {
+            const toml::array& outputs =
+                utility::requireArray(mt["outputs"], file, elemPath + ".outputs");
+            RecipeOutputGroup group;
+            group.items = parseRecipeOutputs(outputs, file, elemPath + ".outputs");
+            def.outputGroups.push_back(std::move(group));
         }
 
         cfg.recipes.push_back(std::move(def));

src/lib/config/RecipesConfig.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <algorithm>
 #include <optional>
 #include <string>
 #include <vector>
@@ -14,14 +15,22 @@ struct RecipeIngredient
     int amount;
 };
 
-// One entry in [[recipe]].outputs. For reprocessing_plant recipes, probability
-// is populated and outputs are rolled with weighted pick at cycle start
-// (REQ-BLD-REPROCESSING, REQ-MAT-CYCLE). For other buildings, probability is
-// std::nullopt and all outputs are produced on every cycle.
+// One item produced by an output group -- amount units of a named item
+// (REQ-MAT-OUTPUT-GROUP).
 struct RecipeOutput
 {
     std::string item;
     int amount;
+};
+
+// One possible result of a production cycle: the items it yields, produced together, and
+// the weight this group is picked with among the recipe's groups (REQ-MAT-OUTPUT-GROUP).
+// A recipe with a single group always produces it, so the weight is meaningful only where
+// there are several -- which is the only difference between what used to be called a
+// deterministic and a probabilistic recipe.
+struct RecipeOutputGroup
+{
+    std::vector<RecipeOutput> items;
     std::optional<double> probability;
 };
 
@@ -30,12 +39,9 @@ struct RecipeDef
     std::string id;                // Unique recipe id; used by UI for selection.
     BuildingType building;         // Which BuildingType can run this recipe.
     std::vector<RecipeIngredient> inputs;
-    std::vector<RecipeOutput> outputs;
+    // Never empty: one group is the ordinary recipe (REQ-MAT-OUTPUT-GROUP).
+    std::vector<RecipeOutputGroup> outputGroups;
     double durationSeconds;
-    // Optional id of the item whose icon represents this recipe in the recipe-
-    // selection dialog (REQ-UI-RECIPE-ICON). When unset, the first output item is
-    // used. A missing icon file for that item is not an error (REQ-UI-ITEM-ICON).
-    std::optional<std::string> icon;
     // Assembler only. When true, this recipe is available from game start
     // regardless of the implicit item graph — used for base recipes that no
     // schematic's materials reach (e.g. building blocks). See REQ-LOCK-IMPLICIT.
@@ -44,6 +50,38 @@ struct RecipeDef
     bool unlockedAtStart = false;
 };
 
+// Every distinct item any group of this recipe can produce, in config order. Most callers
+// only want to know what a recipe can make at all -- which items it has buffers for, which
+// recipes produce an item -- and not which group yields what.
+inline std::vector<std::string> getProducibleItems(const RecipeDef& recipe)
+{
+    std::vector<std::string> items;
+    for (const RecipeOutputGroup& group : recipe.outputGroups)
+    {
+        for (const RecipeOutput& out : group.items)
+        {
+            if (std::find(items.begin(), items.end(), out.item) == items.end())
+            {
+                items.push_back(out.item);
+            }
+        }
+    }
+    return items;
+}
+
+// True when some group of this recipe yields the given item.
+inline bool producesItem(const RecipeDef& recipe, const std::string& itemId)
+{
+    for (const RecipeOutputGroup& group : recipe.outputGroups)
+    {
+        for (const RecipeOutput& out : group.items)
+        {
+            if (out.item == itemId) { return true; }
+        }
+    }
+    return false;
+}
+
 struct RecipesConfig
 {
     std::vector<RecipeDef> recipes;

src/lib/config/ShipsConfig.h

@@ -63,4 +63,19 @@ struct ShipsConfig
         }
         return nullptr;
     }
+
+    // The definition to configure a layout against, or nullptr when there is no layout
+    // to configure: no schematic is selected at all (the empty id the "(None)" option
+    // sets, REQ-UI-SELECT-OPTIONS), the id names no ship, or the ship defines no layout
+    // grid. Every entry to the layout configuration dialog asks this before opening it
+    // and the panel asks it before offering the button that opens it, so the dialog
+    // cannot appear over a grid with no cells (REQ-MOD-UI-DIALOG, REQ-MOD-UI-PREVIEW,
+    // REQ-MOD-UI-AUTO-DIALOG).
+    const ShipDef* findLayoutShipDef(const std::string& id) const
+    {
+        if (id.empty()) { return nullptr; }
+        const ShipDef* def = findShipDef(id);
+        if (!def || def->layout.empty()) { return nullptr; }
+        return def;
+    }
 };

src/lib/core/BuildModeController.cpp

@@ -72,6 +72,7 @@ void BuildModeController::enterMode(BuildMode mode)
             std::make_shared<BuilderModeExitedEvent>());
         break;
     case BuildMode::Blueprint:
+        m_hoveredGhostIsTransfer = false;
         EventManager::getInstance()->sendEventImmediately(
             std::make_shared<BlueprintModeExitedEvent>());
         break;
@@ -134,6 +135,17 @@ void BuildModeController::exitCurrentMode()
     enterMode(BuildMode::None);
 }
 
+void BuildModeController::clearHover()
+{
+    m_ghostTile.reset();
+    m_ghostValid      = false;
+    m_tunnelGhostType = BuildingType::TunnelEntry;
+    m_tunnelPartnerTile.reset();
+    m_blueprintGhostTile.reset();
+    m_hoveredGhostIsTransfer = false;
+    m_deconstructHoverBuildingId.reset();
+}
+
 BuildingType BuildModeController::getBuilderType() const
 {
     return m_builderType;
@@ -149,7 +161,7 @@ BuildingType BuildModeController::getEffectiveBuilderType() const
     return isTunnelMode() ? m_tunnelGhostType : m_builderType;
 }
 
-QPoint BuildModeController::getGhostTile() const
+const std::optional<QPoint>& BuildModeController::getGhostTile() const
 {
     return m_ghostTile;
 }
@@ -239,7 +251,7 @@ Blueprint& BuildModeController::getMutableBlueprint()
     return m_blueprint;
 }
 
-QPoint BuildModeController::getBlueprintGhostTile() const
+const std::optional<QPoint>& BuildModeController::getBlueprintGhostTile() const
 {
     return m_blueprintGhostTile;
 }
@@ -249,6 +261,16 @@ void BuildModeController::setBlueprintGhostTile(QPoint tile)
     m_blueprintGhostTile = tile;
 }
 
+bool BuildModeController::isHoveredGhostTransfer() const
+{
+    return m_hoveredGhostIsTransfer;
+}
+
+void BuildModeController::setHoveredGhostTransfer(bool transfer)
+{
+    m_hoveredGhostIsTransfer = transfer;
+}
+
 const std::optional<BuildingId>&
 BuildModeController::getDeconstructHoverBuildingId() const
 {

src/lib/core/BuildModeController.h

@@ -54,6 +54,15 @@ public:
     // Backs out of whichever mode is active, if any (the Q key and right-click).
     void exitCurrentMode();
 
+    // --- hover ----------------------------------------------------------------
+    // Drops everything that follows from a cursor pointing at the world — both
+    // ghost tiles, placement validity, the resolved tunnel end, the transfer flag,
+    // the deconstruct hover — for a cursor that points at no tile at all, because it
+    // rests on a panel or has left the window (REQ-BLD-GHOST). The active mode is
+    // untouched: the player is still building, just not over anything. A belt drag's
+    // path is untouched too, since a drag keeps hovering while the button is held.
+    void clearHover();
+
     // --- builder mode ---------------------------------------------------------
     // Only meaningful while isBuilderMode().
     BuildingType getBuilderType() const;
@@ -64,7 +73,9 @@ public:
     // tunnel mode, the plain builder type otherwise.
     BuildingType getEffectiveBuilderType() const;
 
-    QPoint   getGhostTile() const;
+    // Unset while the cursor points at no tile (clearHover), which is the one case
+    // where builder mode draws no ghost at all.
+    const std::optional<QPoint>& getGhostTile() const;
     Rotation getGhostRotation() const;
     bool     isGhostValid() const;
     void     setGhostTile(QPoint tile);
@@ -92,9 +103,19 @@ public:
     // Mutable so the caller can rotate the layout in place; rotating a blueprint
     // needs building footprints from the config, which does not belong here.
     Blueprint&       getMutableBlueprint();
-    QPoint           getBlueprintGhostTile() const;
+    // Unset for a cursor pointing at no tile, as for the builder ghost above.
+    const std::optional<QPoint>& getBlueprintGhostTile() const;
     void             setBlueprintGhostTile(QPoint tile);
 
+    // Whether the ghost under the cursor would hand its settings to the building
+    // already there rather than place anything (REQ-UI-BLUEPRINT-TRANSFER). Classifying
+    // it needs the factory state, so the caller resolves it and stores the answer here,
+    // as with setGhostValidity. Kept here rather than recomputed per reader so the
+    // click, the ghost's colour, and the controls panel cannot disagree about what the
+    // cursor is over.
+    bool isHoveredGhostTransfer() const;
+    void setHoveredGhostTransfer(bool transfer);
+
     // --- deconstruct mode -----------------------------------------------------
     const std::optional<BuildingId>& getDeconstructHoverBuildingId() const;
     void setDeconstructHoverBuildingId(std::optional<BuildingId> id);
@@ -106,7 +127,7 @@ private:
     BuildMode m_mode = BuildMode::None;
 
     BuildingType          m_builderType    = BuildingType::Belt;
-    QPoint                m_ghostTile;
+    std::optional<QPoint> m_ghostTile;
     Rotation              m_ghostRotation  = Rotation::East;
     bool                  m_ghostValid     = false;
     BuildingType          m_tunnelGhostType = BuildingType::TunnelEntry;
@@ -116,8 +137,9 @@ private:
     QPoint                    m_beltDragAnchor;
     std::vector<BeltPathTile> m_beltDragPath;
 
-    Blueprint m_blueprint;
-    QPoint    m_blueprintGhostTile;
+    Blueprint             m_blueprint;
+    std::optional<QPoint> m_blueprintGhostTile;
+    bool                  m_hoveredGhostIsTransfer = false;
 
     std::optional<BuildingId> m_deconstructHoverBuildingId;
 };

src/lib/core/BuildingType.cpp

@@ -59,6 +59,8 @@ bool isConfigurableBuildingType(BuildingType type)
     {
     case BuildingType::Miner:      // recipe (REQ-BLD-MINER)
     case BuildingType::Assembler:  // recipe (REQ-BLD-ASSEMBLER)
+    case BuildingType::Smelter:           // recipe (REQ-BLD-AUTO-RECIPE)
+    case BuildingType::ReprocessingPlant:  // recipe (REQ-BLD-AUTO-RECIPE)
     case BuildingType::Shipyard:   // schematic and layout (REQ-BLD-SHIPYARD, REQ-MOD-LAYOUT)
     case BuildingType::Splitter:   // output filters (REQ-BLD-SPLITTER)
         return true;

src/lib/core/BuildingType.h

@@ -30,9 +30,9 @@ std::optional<BuildingType> parseBuildingType(const std::string& id);
 // Canonical id string for a BuildingType. The inverse of parseBuildingType.
 std::string buildingTypeId(BuildingType type);
 
-// Smelter and Reprocessing Plant have no player-selected recipe
-// (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING). They auto-process whatever inputs
-// they receive, matching against every recipe of their building type.
+// Smelter and Reprocessing Plant pick a recipe for themselves from the first material
+// offered to them while they have none (REQ-BLD-AUTO-RECIPE). In every other respect
+// their recipe is selected and held exactly as any other building's.
 bool isAutoRecipeBuildingType(BuildingType type);
 
 // Buildings that run a production cycle: Miner, Smelter, Assembler, Reprocessing
@@ -45,7 +45,9 @@ bool isProductionBuildingType(BuildingType type);
 bool isBeltSubsystemType(BuildingType type);
 
 // Building types with player-facing settings that a blueprint can carry and hand to an
-// existing building (REQ-UI-BLUEPRINT-TRANSFER): Miner and Assembler (recipe), Shipyard
-// (schematic and module layout), Splitter (output filters). Every other type has nothing
-// to configure, so a blueprint of one has nothing to transfer.
+// existing building (REQ-UI-BLUEPRINT-TRANSFER): Miner, Assembler, Smelter and
+// Reprocessing Plant (recipe -- the last two select their own when they have none,
+// REQ-BLD-AUTO-RECIPE), Shipyard (schematic and module layout), Splitter (output
+// filters). Every other type has nothing to configure, so a blueprint of one has
+// nothing to transfer.
 bool isConfigurableBuildingType(BuildingType type);

src/lib/core/CMakeLists.txt

@@ -16,8 +16,11 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/TunnelCompletion.h
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldCoordinates.h
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldCamera.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/FloatingPanelPlacement.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/SelectionBox.h
     ${CMAKE_CURRENT_SOURCE_DIR}/SelectionController.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildModeController.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlAction.h
     PARENT_SCOPE
 )
 
@@ -31,8 +34,10 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/TunnelCompletion.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldCoordinates.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldCamera.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/FloatingPanelPlacement.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/SelectionController.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildModeController.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlAction.cpp
     PARENT_SCOPE
 )
 

src/lib/core/ControlAction.cpp

@@ -0,0 +1,281 @@
+#include "ControlAction.h"
+
+namespace
+{
+
+// A binding that a belt drag can take over. Availability is a property of the action,
+// but a binding can be claimed by a different action while a gesture is in progress:
+// right-click cancels the drag instead of leaving builder mode (REQ-BLD-BELT-DRAG), so
+// ExitMode's right-click drops out and it is left with Q alone.
+enum class BindingCondition
+{
+    Always,
+    NotDraggingBelt
+};
+
+struct KeyBindingEntry
+{
+    ControlAction         action;
+    int                   key;
+    // Shown on the badge, and Ctrl additionally participates in matching. Every other
+    // modifier is display only -- see resolveKeyAction.
+    Qt::KeyboardModifiers modifiers;
+};
+
+struct MouseBindingEntry
+{
+    ControlAction    action;
+    MouseBinding     binding;
+    BindingCondition condition;
+};
+
+// Resolution is first-match-wins over these tables, so an entry that must beat another
+// on the same input is listed above it -- CancelBeltLine before ExitMode on the right
+// mouse button. Everything else is disjoint by availability: Q carries three actions
+// whose availability rules partition the situations between them, so their order here is
+// the order the reader meets them and nothing more (REQ-UI-HOTKEYS).
+const KeyBindingEntry KEY_BINDINGS[] = {
+    {ControlAction::Move,             Qt::Key_A,      Qt::NoModifier},
+    {ControlAction::Move,             Qt::Key_D,      Qt::NoModifier},
+    {ControlAction::GameSpeed,        Qt::Key_W,      Qt::NoModifier},
+    {ControlAction::GameSpeed,        Qt::Key_S,      Qt::NoModifier},
+    {ControlAction::TogglePause,      Qt::Key_Space,  Qt::NoModifier},
+    {ControlAction::CopyTemporary,    Qt::Key_C,      Qt::NoModifier},
+    {ControlAction::CreateBlueprint,  Qt::Key_C,      Qt::ControlModifier},
+    {ControlAction::PasteTemporary,   Qt::Key_V,      Qt::NoModifier},
+    {ControlAction::OpenBlueprints,   Qt::Key_V,      Qt::ControlModifier},
+    // One binding, two badges: Shift picks the rotation direction and is read by the
+    // handler, the way a build hotkey's digit is (REQ-BLD-ROTATE). Both entries match
+    // the same press, and both resolve to the same action, so listing them twice costs
+    // nothing and is what puts "R" and "Shift+R" on the row.
+    {ControlAction::Rotate,           Qt::Key_R,      Qt::NoModifier},
+    {ControlAction::Rotate,           Qt::Key_R,      Qt::ShiftModifier},
+    {ControlAction::ExitMode,         Qt::Key_Q,      Qt::NoModifier},
+    {ControlAction::ClearSelection,   Qt::Key_Q,      Qt::NoModifier},
+    {ControlAction::EnterDeconstruct, Qt::Key_Q,      Qt::NoModifier},
+    {ControlAction::OpenMenu,         Qt::Key_Escape, Qt::NoModifier},
+};
+
+const MouseBindingEntry MOUSE_BINDINGS[] = {
+    {ControlAction::Select,             MouseBinding::LeftClick,     BindingCondition::Always},
+    {ControlAction::Place,              MouseBinding::LeftClick,     BindingCondition::Always},
+    {ControlAction::ApplySettings,      MouseBinding::LeftClick,     BindingCondition::Always},
+    {ControlAction::ToggleDeconstruct,  MouseBinding::LeftClick,     BindingCondition::Always},
+    {ControlAction::SelectArea,         MouseBinding::LeftDrag,      BindingCondition::Always},
+    {ControlAction::PlaceBeltLine,      MouseBinding::LeftDrag,      BindingCondition::Always},
+    {ControlAction::DeconstructArea,    MouseBinding::LeftDrag,      BindingCondition::Always},
+    {ControlAction::AddToSelection,     MouseBinding::CtrlLeftClick, BindingCondition::Always},
+    {ControlAction::AddAreaToSelection, MouseBinding::CtrlLeftDrag,  BindingCondition::Always},
+    {ControlAction::CancelBeltLine,     MouseBinding::RightClick,    BindingCondition::Always},
+    {ControlAction::ExitMode,           MouseBinding::RightClick,    BindingCondition::NotDraggingBelt},
+};
+
+bool isConditionMet(BindingCondition condition, const ControlContext& context)
+{
+    if (condition == BindingCondition::NotDraggingBelt) { return !context.draggingBelt; }
+    return true;
+}
+
+bool isPlacementMode(const ControlContext& context)
+{
+    return context.mode == BuildMode::Builder || context.mode == BuildMode::Blueprint;
+}
+
+std::vector<ControlAction> filterAvailable(const std::vector<ControlAction>& actions,
+                                           const ControlContext& context)
+{
+    std::vector<ControlAction> available;
+    for (ControlAction action : actions)
+    {
+        if (isControlActionAvailable(action, context)) { available.push_back(action); }
+    }
+    return available;
+}
+
+}  // namespace
+
+bool isControlActionAvailable(ControlAction action, const ControlContext& context)
+{
+    switch (action)
+    {
+    case ControlAction::None:
+        return false;
+
+    case ControlAction::Move:
+    case ControlAction::GameSpeed:
+    case ControlAction::TogglePause:
+    case ControlAction::OpenBlueprints:
+    case ControlAction::OpenMenu:
+        return true;
+
+    // Does nothing until something has been captured with C, so it is not offered
+    // before then (REQ-UI-BLUEPRINT-TEMP, REQ-UI-CONTROLS-ACCURACY).
+    case ControlAction::PasteTemporary:
+        return context.temporaryBlueprintExists;
+
+    case ControlAction::Select:
+    case ControlAction::SelectArea:
+    case ControlAction::AddToSelection:
+    case ControlAction::AddAreaToSelection:
+        return context.mode == BuildMode::None;
+
+    // The three cases of Q, in the order REQ-UI-HOTKEYS evaluates them: it leaves the
+    // active mode, else clears the selection, else enters deconstruct mode. A selection
+    // and a build mode never coexist (REQ-UI-SELECTION-EXCLUSIVE), so the first two are
+    // already disjoint; what the empty-selection condition below adds is the third step,
+    // which is why entering deconstruct mode by key takes two presses while something is
+    // selected -- the Deconstruct button still gets there in one click.
+    case ControlAction::ClearSelection:
+        return context.mode == BuildMode::None
+               && context.selection != ControlSelection::None;
+    case ControlAction::EnterDeconstruct:
+        return context.mode == BuildMode::None
+               && context.selection == ControlSelection::None;
+
+    // Both need something a blueprint can be made of; a selection of ships or debris
+    // leaves them inert (REQ-UI-HOTKEYS).
+    case ControlAction::CopyTemporary:
+    case ControlAction::CreateBlueprint:
+        return context.mode == BuildMode::None && context.placeableBuildingSelected;
+
+    // Place and ApplySettings are the same click; which one it is depends on whether
+    // the ghost under the cursor is a transfer target (REQ-UI-BLUEPRINT-TRANSFER).
+    case ControlAction::Place:
+        return isPlacementMode(context) && !context.hoveredGhostIsTransfer;
+    case ControlAction::ApplySettings:
+        return context.mode == BuildMode::Blueprint && context.hoveredGhostIsTransfer;
+
+    // The only building type placed by dragging (REQ-BLD-BELT-DRAG).
+    case ControlAction::PlaceBeltLine:
+        return context.mode == BuildMode::Builder
+               && context.builderType == BuildingType::Belt;
+
+    case ControlAction::Rotate:
+        return isPlacementMode(context);
+    case ControlAction::CancelBeltLine:
+        return context.draggingBelt;
+    case ControlAction::ExitMode:
+        return context.mode != BuildMode::None;
+
+    case ControlAction::ToggleDeconstruct:
+    case ControlAction::DeconstructArea:
+        return context.mode == BuildMode::Deconstruct;
+    }
+    return false;
+}
+
+std::vector<ControlBinding> getControlActionBindings(ControlAction action,
+                                                     const ControlContext& context)
+{
+    std::vector<ControlBinding> bindings;
+    for (const MouseBindingEntry& entry : MOUSE_BINDINGS)
+    {
+        if (entry.action != action)                    { continue; }
+        if (!isConditionMet(entry.condition, context)) { continue; }
+        ControlBinding binding;
+        binding.isMouse = true;
+        binding.mouse   = entry.binding;
+        bindings.push_back(binding);
+    }
+    for (const KeyBindingEntry& entry : KEY_BINDINGS)
+    {
+        if (entry.action != action) { continue; }
+        ControlBinding binding;
+        binding.key       = entry.key;
+        binding.modifiers = entry.modifiers;
+        bindings.push_back(binding);
+    }
+    return bindings;
+}
+
+ControlContextKind getControlContextKind(const ControlContext& context)
+{
+    switch (context.mode)
+    {
+    case BuildMode::Builder:     return ControlContextKind::Build;
+    case BuildMode::Blueprint:   return ControlContextKind::Blueprint;
+    case BuildMode::Deconstruct: return ControlContextKind::Deconstruct;
+    case BuildMode::None:        break;
+    }
+    return context.selection == ControlSelection::None ? ControlContextKind::General
+                                                       : ControlContextKind::Selection;
+}
+
+std::vector<ControlAction> getContextActions(const ControlContext& context)
+{
+    // The candidates of each context, in the order REQ-UI-CONTROLS-CONTENT lists them,
+    // then filtered by availability.
+    //
+    // The General and Selection lists differ rather than one filtered list serving
+    // both, because the additive-selection rows are an omission and not an
+    // unavailability: Ctrl+click does work with nothing selected, it just picks the
+    // object like a plain click would. "Add / remove from selection" is a row that
+    // means nothing until there is a selection to add to, so it waits for one
+    // (REQ-UI-CONTROLS-ACCURACY permits omitting an available binding).
+    switch (getControlContextKind(context))
+    {
+    case ControlContextKind::Build:
+    case ControlContextKind::Blueprint:
+        return filterAvailable({ControlAction::Place, ControlAction::ApplySettings,
+                                ControlAction::PlaceBeltLine, ControlAction::Rotate,
+                                ControlAction::CancelBeltLine, ControlAction::ExitMode},
+                               context);
+    case ControlContextKind::Deconstruct:
+        return filterAvailable({ControlAction::ToggleDeconstruct,
+                                ControlAction::DeconstructArea, ControlAction::ExitMode},
+                               context);
+    // ClearSelection is listed last for the same reason ExitMode is above: the row that
+    // backs the player out of the context sits at the bottom of the context's rows
+    // wherever there is one (REQ-UI-CONTROLS-CONTENT).
+    case ControlContextKind::Selection:
+        return filterAvailable({ControlAction::Select, ControlAction::SelectArea,
+                                ControlAction::AddToSelection,
+                                ControlAction::AddAreaToSelection,
+                                ControlAction::CopyTemporary,
+                                ControlAction::CreateBlueprint,
+                                ControlAction::ClearSelection},
+                               context);
+    case ControlContextKind::General:
+        break;
+    }
+    return filterAvailable({ControlAction::Select, ControlAction::SelectArea,
+                            ControlAction::EnterDeconstruct},
+                           context);
+}
+
+std::vector<ControlAction> getAlwaysAvailableActions(const ControlContext& context)
+{
+    return filterAvailable({ControlAction::Move, ControlAction::GameSpeed,
+                            ControlAction::TogglePause, ControlAction::PasteTemporary,
+                            ControlAction::OpenBlueprints, ControlAction::OpenMenu},
+                           context);
+}
+
+ControlAction resolveKeyAction(int key, Qt::KeyboardModifiers modifiers,
+                               const ControlContext& context)
+{
+    // Ctrl distinguishes a chord from the bare key (Ctrl+C is not C); every other
+    // modifier is ignored, so Shift+A still pans and Shift+R still rotates. This is
+    // what the key handler has always done, and matching modifiers exactly instead
+    // would silently drop those presses.
+    const bool controlHeld = (modifiers & Qt::ControlModifier) != 0;
+    for (const KeyBindingEntry& entry : KEY_BINDINGS)
+    {
+        if (entry.key != key) { continue; }
+        const bool entryNeedsControl = (entry.modifiers & Qt::ControlModifier) != 0;
+        if (entryNeedsControl != controlHeld) { continue; }
+        if (isControlActionAvailable(entry.action, context)) { return entry.action; }
+    }
+    return ControlAction::None;
+}
+
+ControlAction resolveMouseAction(MouseBinding binding, const ControlContext& context)
+{
+    for (const MouseBindingEntry& entry : MOUSE_BINDINGS)
+    {
+        if (entry.binding != binding)                        { continue; }
+        if (!isConditionMet(entry.condition, context))       { continue; }
+        if (isControlActionAvailable(entry.action, context)) { return entry.action; }
+    }
+    return ControlAction::None;
+}

src/lib/core/ControlAction.h

@@ -0,0 +1,168 @@
+#pragma once
+
+#include <vector>
+
+#include <Qt>
+
+#include "BuildModeController.h"
+#include "BuildingType.h"
+
+// The single statement of what the player can do right now, and which input does it
+// (REQ-UI-CONTROLS-CONTENT, REQ-UI-CONTROLS-ACCURACY).
+//
+// This file declares actions; it never performs them and it never names them. It knows
+// an action's bindings and the situations in which it does something -- nothing about
+// the simulation, the widgets, the events an action ends up firing, or the words shown
+// to the player. Display text lives in ui/ControlActionText.h, which formats the
+// bindings this hands it, so a badge is derived from the real binding rather than
+// typed beside it.
+//
+// Three readers, all of them consuming this and none of them extending it:
+//
+//  * ControlsPanel calls getContextActions()/getAlwaysAvailableActions() and draws them.
+//  * InputMapper calls resolveKeyAction() and fires the event the action stands for.
+//  * GameWorldView calls resolveMouseAction() and runs the branch it already ran.
+//
+// Two bindings are deliberately absent. Build hotkeys (REQ-UI-HOTKEYS) are advertised
+// on the build buttons instead of in the panel, and InputMapper::getBuildHotkeyLabel
+// already derives their badges from the same table the handler switches on, so they
+// have no drift to fix. F3/F4 are development controls and appear nowhere
+// (REQ-UI-CONTROLS-ACCURACY).
+//
+// When bindings become player-configurable, only the binding tables in the .cpp turn
+// from hard-coded data into loaded data. The actions, the availability rules, the
+// panel, and every handler are unaffected.
+enum class ControlAction
+{
+    None,  // no action is bound to the queried input in the queried context
+
+    // Always available (REQ-UI-CONTROLS-CONTENT).
+    Move,
+    GameSpeed,
+    TogglePause,
+    PasteTemporary,
+    OpenBlueprints,
+    OpenMenu,
+
+    // No build mode active.
+    Select,
+    SelectArea,
+    AddToSelection,
+    AddAreaToSelection,
+    EnterDeconstruct,
+
+    // No build mode active, with something selected.
+    CopyTemporary,
+    CreateBlueprint,
+    ClearSelection,
+
+    // Builder and blueprint placement mode.
+    Place,
+    ApplySettings,
+    PlaceBeltLine,
+    Rotate,
+    CancelBeltLine,
+    ExitMode,
+
+    // Deconstruct mode.
+    ToggleDeconstruct,
+    DeconstructArea
+};
+
+// The mouse gestures that carry a binding. Each is a whole gesture rather than a raw
+// event: a drag is one binding, not a press plus a release, because that is the unit
+// the player and the panel both think in. Which events make up the gesture, and the
+// state it runs on, stay with the widget that owns them.
+enum class MouseBinding
+{
+    LeftClick,
+    LeftDrag,
+    CtrlLeftClick,
+    CtrlLeftDrag,
+    RightClick
+};
+
+// Which selection category is held, mirroring REQ-UI-SELECTION-CATEGORIES without
+// depending on SelectionController.
+enum class ControlSelection
+{
+    None,
+    Buildings,
+    FieldObjects
+};
+
+// Which card the panel is showing (REQ-UI-CONTROLS-CONTENT). Named rather than
+// spelled, so the heading text stays a presentation concern.
+enum class ControlContextKind
+{
+    General,
+    Selection,
+    Build,
+    Blueprint,
+    Deconstruct
+};
+
+// Everything the availability rules are allowed to depend on, as a plain snapshot.
+//
+// Taking a snapshot rather than references to the live controllers is what keeps this
+// testable without a world, and it is what stops an action from reaching into the
+// simulation: if a rule needs a fact, the fact is named here and the caller supplies it.
+struct ControlContext
+{
+    BuildMode        mode                      = BuildMode::None;
+    // While mode == Builder: the type a click would place at the current hover position,
+    // not the type the mode was entered with — tunnel mode resolves to either end
+    // (REQ-BLD-TUNNEL-MODE).
+    BuildingType     builderType               = BuildingType::Belt;
+    bool             draggingBelt              = false;
+    // A single-building blueprint whose ghost is over a configuration-transfer target,
+    // so clicking hands over settings rather than placing (REQ-UI-BLUEPRINT-TRANSFER).
+    bool             hoveredGhostIsTransfer    = false;
+    ControlSelection selection                 = ControlSelection::None;
+    int              selectionCount            = 0;
+    // At least one selected building is player-placeable, the condition under which
+    // C and Ctrl+C do anything (REQ-UI-HOTKEYS).
+    bool             placeableBuildingSelected = false;
+    bool             temporaryBlueprintExists  = false;
+};
+
+// One input an action answers to, in structured form so the badge can be rendered from
+// it. `modifiers` is what the badge shows; matching is looser than equality, see
+// resolveKeyAction.
+struct ControlBinding
+{
+    bool                  isMouse    = false;
+    MouseBinding          mouse      = MouseBinding::LeftClick;
+    int                   key        = 0;  // Qt::Key_*, when !isMouse
+    Qt::KeyboardModifiers modifiers  = Qt::NoModifier;
+};
+
+// True when triggering the action in this context would do what its label says. The
+// panel shows exactly the available actions, and the resolvers return only available
+// ones, which is REQ-UI-CONTROLS-ACCURACY expressed as one function.
+bool isControlActionAvailable(ControlAction action, const ControlContext& context);
+
+// The inputs an action answers to, in the order the panel should badge them.
+// Context-dependent because a binding can be taken over: while a belt drag is in
+// progress the right mouse button cancels the drag, so ExitMode is left with its key
+// binding alone (REQ-BLD-BELT-DRAG).
+std::vector<ControlBinding> getControlActionBindings(ControlAction action,
+                                                     const ControlContext& context);
+
+// Which card is showing, and the rows it holds -- the context's own, then the block
+// available everywhere (REQ-UI-CONTROLS-CARD). Both lists are already filtered to the
+// available actions and ordered as REQ-UI-CONTROLS-CONTENT lists them.
+ControlContextKind         getControlContextKind(const ControlContext& context);
+std::vector<ControlAction> getContextActions(const ControlContext& context);
+std::vector<ControlAction> getAlwaysAvailableActions(const ControlContext& context);
+
+// The action a key press or a mouse gesture triggers here, or None when the input is
+// unbound in this context. Both return only actions that are available, so a caller can
+// act on the result without re-checking the situation.
+//
+// Rotation direction is not part of the action: R and Shift+R are one Rotate, and the
+// caller reads the modifier for the direction, exactly as the digit of a build hotkey
+// is read from the key. An action with a parameter keeps the parameter at the handler.
+ControlAction resolveKeyAction(int key, Qt::KeyboardModifiers modifiers,
+                               const ControlContext& context);
+ControlAction resolveMouseAction(MouseBinding binding, const ControlContext& context);

src/lib/core/EntityAdmin.h

@@ -28,7 +28,7 @@ public:
     void forEach(Func&& f) const;
 
     template <typename... Ts>
-    bool hasAll(entt::entity entity);
+    bool hasAll(entt::entity entity) const;
 
     template <typename T>
     T& get(entt::entity entity);
@@ -101,7 +101,7 @@ void EntityAdmin::forEach(Func&& f) const
 }
 
 template <typename... Ts>
-bool EntityAdmin::hasAll(entt::entity entity)
+bool EntityAdmin::hasAll(entt::entity entity) const
 {
     return m_registry.all_of<Ts...>(entity);
 }

src/lib/core/FloatingPanelPlacement.cpp

@@ -0,0 +1,111 @@
+#include "FloatingPanelPlacement.h"
+
+#include <algorithm>
+
+namespace
+{
+
+// The part every placement shares, whatever put the panel where it wants to be: it is
+// pushed inside band rather than hanging off it, shortened to what its own column has
+// free, and lifted by however much of it hangs below that. wantedLeftPx and wantedTopPx
+// are where the panel would stand if nothing were in the way.
+QRect fitInBand(const QRect& band, int wantedLeftPx, int wantedTopPx, QSize wantedSize,
+                const std::vector<QRect>& occupiedRects, int marginPx)
+{
+    const int widthPx = std::min(wantedSize.width(), band.width());
+
+    int leftPx = std::min(wantedLeftPx, band.right() - widthPx + 1);
+    leftPx     = std::max(leftPx, band.left());
+
+    // Only the widgets its own column meets can shorten it.
+    const int bottomPx = getAvailableBottomPx(band, occupiedRects, leftPx,
+                                              leftPx + widthPx - 1, marginPx);
+    const int heightPx =
+        std::min(wantedSize.height(), std::max(0, bottomPx - band.top() + 1));
+
+    // Never above the band: a panel taller than the space left is capped instead, and
+    // scrolls.
+    int topPx = std::max(wantedTopPx, band.top());
+    topPx     = std::min(topPx, bottomPx - heightPx + 1);
+    topPx     = std::max(topPx, band.top());
+
+    return QRect(leftPx, topPx, widthPx, heightPx);
+}
+
+}  // namespace
+
+
+int getAvailableBottomPx(const QRect& band, const std::vector<QRect>& occupiedRects,
+                         int leftPx, int rightPx, int marginPx)
+{
+    int bottomPx = band.bottom();
+    for (const QRect& occupied : occupiedRects)
+    {
+        if (occupied.isEmpty())
+        {
+            continue;
+        }
+        // Only what is actually in the way counts: a widget entirely to one side of this
+        // span is not below it, however tall it is.
+        if (occupied.right() < leftPx || occupied.left() > rightPx)
+        {
+            continue;
+        }
+        bottomPx = std::min(bottomPx, occupied.top() - marginPx - 1);
+    }
+    return bottomPx;
+}
+
+PanelSide chooseSide(const QRect& band, const QRect& anchorRect, int widthPx,
+                     int selectionGapPx)
+{
+    // What each side offers: the room between the anchor and that edge of the band, less
+    // the gap the panel keeps from the anchor. The band's own inset from the view has
+    // already taken the edge margin off.
+    const int roomRightPx = band.right() - anchorRect.right() - selectionGapPx;
+    const int roomLeftPx  = anchorRect.left() - band.left() - selectionGapPx;
+
+    if (roomRightPx >= widthPx)
+    {
+        return PanelSide::Right;
+    }
+    if (roomLeftPx >= widthPx)
+    {
+        return PanelSide::Left;
+    }
+    // Neither side can hold it without covering the selection, so it goes where it
+    // covers the least of it.
+    return (roomRightPx >= roomLeftPx) ? PanelSide::Right : PanelSide::Left;
+}
+
+QRect placeBesideAnchor(const QRect& band, const QRect& anchorRect, PanelSide side,
+                        QSize wantedSize, const std::vector<QRect>& occupiedRects,
+                        int selectionGapPx, int marginPx)
+{
+    const int widthPx = std::min(wantedSize.width(), band.width());
+
+    // A gap from the anchor on the chosen side, growing away from it: the edge facing the
+    // selection is the one that stays put as the panel's content resizes. A panel that
+    // does not fit there is pushed back inside the view rather than hanging off it, which
+    // is what puts it over the selection when neither side had room.
+    const int wantedLeftPx = (side == PanelSide::Right)
+                                 ? anchorRect.right() + selectionGapPx + 1
+                                 : anchorRect.left() - selectionGapPx - widthPx;
+
+    // Top-aligned with the anchor -- the gap separates the two horizontally and plays no
+    // part here -- then lifted by however much of the panel hangs below what is free.
+    return fitInBand(band, wantedLeftPx, anchorRect.top(), wantedSize, occupiedRects,
+                     marginPx);
+}
+
+QRect placeAtDesiredTopLeft(const QRect& band, const QPoint& desiredTopLeftPx,
+                            QSize wantedSize, const std::vector<QRect>& occupiedRects,
+                            int marginPx)
+{
+    // Where the player dropped it, resolved by the same rules as any other placement
+    // (REQ-UI-SELECTION-PANEL-DRAG). Nothing here is written back to the desired point:
+    // a panel lifted above the build button bar returns to where it was dropped as soon
+    // as the bar stops meeting its column.
+    return fitInBand(band, desiredTopLeftPx.x(), desiredTopLeftPx.y(), wantedSize,
+                     occupiedRects, marginPx);
+}

src/lib/core/FloatingPanelPlacement.h

@@ -0,0 +1,62 @@
+#pragma once
+
+#include <vector>
+
+#include <QPoint>
+#include <QRect>
+#include <QSize>
+
+// Geometry for the widgets floating over the game world view (REQ-UI-WORLD-SIZE). Their
+// owner places them in one ordered pass, each into the space the earlier ones left free,
+// and these are the rules they place themselves by. Pure geometry -- no widget is
+// involved, which is what lets the rules be tested without a display.
+//
+// Two distances run through these rules and are deliberately different (see
+// REQ-UI-SELECTION-PANEL). marginPx is the edge margin: what a widget keeps from the
+// view's edges and from the widgets it steps around. selectionGapPx is the gap the
+// selection panel keeps from the selection it describes -- half a tile, which is the
+// wider of the two, so the panel stands clear of the objects rather than touching them.
+
+// The lowest bottom edge available to a widget occupying the horizontal span
+// [leftPx, rightPx] inside band: the band's own bottom, or marginPx above the topmost
+// occupied rectangle whose horizontal extent meets that span. A rectangle beside the
+// span is not in the way and does not shorten it (REQ-UI-SELECTION-PANEL,
+// REQ-UI-CONTROLS-PANEL). The result is inclusive, as QRect::bottom() is.
+int getAvailableBottomPx(const QRect& band, const std::vector<QRect>& occupiedRects,
+                         int leftPx, int rightPx, int marginPx);
+
+// Which side of the selection the panel stands on (REQ-UI-SELECTION-PANEL).
+enum class PanelSide
+{
+    Right,
+    Left
+};
+
+// The side a panel widthPx wide takes beside anchorRect: the right of it where it fits
+// within band, otherwise the left, and where it fits on neither, whichever side leaves
+// more room -- the one case in which the panel ends up over the selection
+// (REQ-UI-SELECTION-PANEL). The room a side offers is what is left of it once the panel's
+// gap from the selection is taken off. Decided once when the selection starts and kept for
+// as long as it lasts, so a card that grows later never flips the panel across the object.
+PanelSide chooseSide(const QRect& band, const QRect& anchorRect, int widthPx,
+                     int selectionGapPx);
+
+// Where a panel of wantedSize stands beside anchorRect on the given side: separated from
+// it by selectionGapPx and growing away from it, its top edge on the anchor's top edge,
+// pushed inside band and above whatever occupies it. The gap is horizontal only -- the
+// panel's top sits level with the anchor's, however wide the gap. The returned height is
+// short of wantedSize's when there was not enough room, which is the caller's cue to
+// scroll its content (REQ-UI-SELECTION-PANEL).
+QRect placeBesideAnchor(const QRect& band, const QRect& anchorRect, PanelSide side,
+                        QSize wantedSize, const std::vector<QRect>& occupiedRects,
+                        int selectionGapPx, int marginPx);
+
+// Where a panel of wantedSize stands once the player has dragged it to desiredTopLeftPx:
+// at that point, by the same rules that place it beside a selection -- pushed inside band,
+// lifted above whatever occupies its column, and capped in height where that leaves too
+// little room (REQ-UI-SELECTION-PANEL-DRAG). The desired point is an input only: it is
+// never corrected and handed back, which is what lets the caller keep it exactly as
+// dropped and return to it once the room is there again.
+QRect placeAtDesiredTopLeft(const QRect& band, const QPoint& desiredTopLeftPx,
+                            QSize wantedSize, const std::vector<QRect>& occupiedRects,
+                            int marginPx);

src/lib/core/SelectionBox.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <QPoint>
+#include <QRectF>
+#include <QVector2D>
+
+// The coverage rules of a selection box (REQ-UI-MULTI-SELECT, REQ-BLD-DECONSTRUCT-BOX).
+//
+// The box is a rectangle in world coordinates — tiles as the unit, but fractional,
+// because the drag follows the mouse and is not snapped to the tile grid. The two
+// rules below are the whole of what "covered by the box" means; they live here so the
+// building query and the entity queries answer it identically.
+//
+// Both callers pass a normalized rectangle: neither rule normalizes on its own.
+
+// Whether the box overlaps the unit square of `tile` — the rule for anything that
+// occupies whole tiles (buildings, construction sites, defence station bodies). The
+// comparisons are inclusive, so a box that only grazes the tile's edge still covers
+// it, and a box with no area covers the tile it lies on.
+inline bool boxCoversTile(const QRectF& worldBox, QPoint tile)
+{
+    return worldBox.left() <= static_cast<qreal>(tile.x()) + 1.0
+        && worldBox.right() >= static_cast<qreal>(tile.x())
+        && worldBox.top() <= static_cast<qreal>(tile.y()) + 1.0
+        && worldBox.bottom() >= static_cast<qreal>(tile.y());
+}
+
+// Whether the box contains `worldPos` — the rule for anything that has a position
+// rather than a footprint (ships, debris). Their centre is what the box must enclose,
+// so that what the rectangle visibly holds is what the drag selects.
+inline bool boxCoversPoint(const QRectF& worldBox, QVector2D worldPos)
+{
+    return worldBox.contains(QPointF(worldPos.x(), worldPos.y()));
+}

src/lib/eventsystem/event/CMakeLists.txt

@@ -9,6 +9,7 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/BossWaveUpdatedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/SchematicChoicesAvailableEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/SelectionChangedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/SelectionAnchorChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/GameOverEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/GameResetEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/WinEvent.h
@@ -24,6 +25,7 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/SpeedStepRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/GhostRotationRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/ModeCancelRequestedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/SelectionClearRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/DebugDrawToggleRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/DeconstructModeChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BuildingTypeSelectedEvent.h
@@ -43,6 +45,7 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/BeamFiredEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/DebugDrawToggledEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/CommandRequestedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/FloatingLayoutInvalidatedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/PlayerCommandsAppliedEvent.h
 	PARENT_SCOPE
 )

src/lib/eventsystem/event/FloatingLayoutInvalidatedEvent.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include "Event.h"
+
+// Asks the owner of the widgets floating over the game world view to re-run its placement
+// pass (see ui/FloatingPanel.h). Published by a floating widget whose content or
+// visibility changed: what space that widget may take depends on the ones placed before
+// it, so it cannot re-place itself alone (REQ-UI-BUILD-BAR, REQ-UI-CONTROLS-PANEL,
+// REQ-UI-SELECTION-PANEL). Carries no payload -- the pass re-reads every widget.
+class FloatingLayoutInvalidatedEvent : public Event
+{
+};

src/lib/eventsystem/event/SelectionAnchorChangedEvent.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <QRect>
+
+#include "Event.h"
+
+// Where on the screen the selection that is about to be made sits: the bounds of the one
+// object selected, or of all of them when the selection starts as a multi-selection
+// (REQ-UI-SELECTION-PANEL). The rectangle is in the game world view's own widget
+// coordinates.
+//
+// Published only when a selection *starts* -- a plain click or drag, or an additive one
+// onto an empty selection -- and always immediately before the selection itself. Adding
+// to a selection publishes nothing, which is what leaves the selection panel where it
+// is while the selection grows; and because the rectangle is screen space frozen at that
+// moment, scrolling the view or a selected ship flying off does not move the panel
+// either.
+//
+// The gap the panel keeps from that rectangle travels with it, for the same reason: it is
+// half a tile as the tile stood in this moment (REQ-UI-SELECTION-PANEL, REQ-GW-TILE-SIZE)
+// and stays that for as long as the selection lasts, a rectangle frozen in one moment
+// having no meaningful distance to a tile size measured in another.
+class SelectionAnchorChangedEvent : public Event
+{
+public:
+    SelectionAnchorChangedEvent(QRect rectPx, int selectionGapPx)
+        : rectPx(rectPx), selectionGapPx(selectionGapPx) {}
+
+    const QRect rectPx;
+    const int   selectionGapPx;
+};

src/lib/eventsystem/event/SelectionClearRequestedEvent.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include "Event.h"
+
+// The player pressed the key that drops the current selection (REQ-UI-HOTKEYS). Separate
+// from ModeCancelRequestedEvent although both are Q: which of the two a press means is
+// settled by the action table, and an event that meant either would force the receiver to
+// decide it a second time.
+class SelectionClearRequestedEvent : public Event
+{
+};

src/lib/sim/Building.h

@@ -27,11 +27,14 @@ struct InputBuffer
     std::map<ItemType, int> caps;    // max items per material (2× per-cycle requirement)
 };
 
-// Output buffer shared by all output materials for a production building.
+// Per-material output buffer for a production building. The items are held in one
+// production-ordered queue -- that is the order they leave at the output port
+// (REQ-MAT-OUTPUT-EMERGE) -- while the capacity is per item type, so one item's backlog
+// never occupies another's room (REQ-MAT-OUTPUT-BUFFER).
 struct OutputBuffer
 {
-    std::vector<Item> items;
-    int capacity = 0;  // 2× per-cycle output; 1× for ReprocessingPlant
+    std::vector<Item>       items;  // production order; feeds the output belt
+    std::map<ItemType, int> caps;   // max items per material (2x its per-cycle amount)
 };
 
 // Active production cycle for a building.
@@ -96,6 +99,25 @@ struct Building
         return count;
     }
 
+    // The same over one material, which is what its own capacity is measured against
+    // (REQ-MAT-OUTPUT-BUFFER).
+    int getOutputItemCount(const ItemType& type) const
+    {
+        int count = 0;
+        for (const Item& item : outputBuffer.items)
+        {
+            if (item.type == type) { ++count; }
+        }
+        for (const std::vector<BeltItemSlot>& lane : emergingItems)
+        {
+            for (const BeltItemSlot& slot : lane)
+            {
+                if (slot.item.type == type) { ++count; }
+            }
+        }
+        return count;
+    }
+
     // Items currently travelling inward on each input port's virtual input belt
     // (REQ-MAT-INPUT-INTAKE); one lane per input port, parallel to inputPorts. Each
     // lane holds slots at progress [0.0, 0.5], front (highest progress) first. An

src/lib/sim/BuildingBuffers.cpp

@@ -2,12 +2,48 @@
 
 #include <algorithm>
 #include <cassert>
+#include <map>
 
 #include "BuildingType.h"
 #include "ItemType.h"
 #include "ModulesConfig.h"
 #include "ShipsConfig.h"
 
+namespace
+{
+
+// Folds the output capacities one recipe implies into `caps`: twice each produced item's
+// per-cycle amount (REQ-MAT-OUTPUT-BUFFER). A cycle yields exactly one output group
+// (REQ-MAT-OUTPUT-GROUP), so an item's per-cycle amount is the largest total any single
+// group produces of it -- summed within a group, whose items come together, and taken at
+// its maximum across groups, of which only one ever happens.
+//
+// Where a cap is already present the larger wins, which is how a cap unions across the
+// recipes it could be sized over -- the same rule the input caps follow.
+void addOutputCaps(std::map<ItemType, int>& caps, const RecipeDef& recipe)
+{
+    std::map<ItemType, int> perCycle;
+    for (const RecipeOutputGroup& group : recipe.outputGroups)
+    {
+        std::map<ItemType, int> inGroup;
+        for (const RecipeOutput& out : group.items)
+        {
+            inGroup[ItemType{out.item}] += out.amount;
+        }
+        for (const std::pair<const ItemType, int>& entry : inGroup)
+        {
+            perCycle[entry.first] = std::max(perCycle[entry.first], entry.second);
+        }
+    }
+
+    for (const std::pair<const ItemType, int>& entry : perCycle)
+    {
+        caps[entry.first] = std::max(caps[entry.first], 2 * entry.second);
+    }
+}
+
+}  // namespace
+
 void initBuffers(Building& b, const RecipeDef& recipe)
 {
     b.inputBuffer.counts.clear();
@@ -20,87 +56,18 @@ void initBuffers(Building& b, const RecipeDef& recipe)
     }
 
     b.outputBuffer.items.clear();
-    if (b.type == BuildingType::ReprocessingPlant)
-    {
-        // 1× max-per-roll (REQ-MAT-OUTPUT-BUFFER-REPROCESSING).
-        int maxAmount = 0;
-        for (const RecipeOutput& out : recipe.outputs)
-        {
-            if (out.amount > maxAmount)
-            {
-                maxAmount = out.amount;
-            }
-        }
-        b.outputBuffer.capacity = maxAmount;
-    }
-    else
-    {
-        // 2× per-cycle output.
-        int totalAmount = 0;
-        for (const RecipeOutput& out : recipe.outputs)
-        {
-            totalAmount += out.amount;
-        }
-        b.outputBuffer.capacity = 2 * totalAmount;
-    }
-}
-
-void initAutoBuffers(const GameConfig& config, Building& b)
-{
-    b.inputBuffer.counts.clear();
-    b.inputBuffer.caps.clear();
-
-    // Union the inputs of every recipe of this building type; the cap for each
-    // item is twice the largest per-cycle requirement across those recipes.
-    // Output capacity follows the same rules as initBuffers: the Reprocessing
-    // Plant holds one cycle's max output (REQ-MAT-OUTPUT-BUFFER-REPROCESSING),
-    // other auto buildings hold twice the largest per-cycle output.
-    int outputCapacity = 0;
-    for (const RecipeDef& recipe : config.recipes.recipes)
-    {
-        if (recipe.building != b.type)
-        {
-            continue;
-        }
-
-        for (const RecipeIngredient& ing : recipe.inputs)
-        {
-            const ItemType type{ing.item};
-            b.inputBuffer.counts[type] = 0;
-            b.inputBuffer.caps[type] =
-                std::max(b.inputBuffer.caps[type], 2 * ing.amount);
-        }
-
-        if (b.type == BuildingType::ReprocessingPlant)
-        {
-            int maxAmount = 0;
-            for (const RecipeOutput& out : recipe.outputs)
-            {
-                maxAmount = std::max(maxAmount, out.amount);
-            }
-            outputCapacity = std::max(outputCapacity, maxAmount);
-        }
-        else
-        {
-            int totalAmount = 0;
-            for (const RecipeOutput& out : recipe.outputs)
-            {
-                totalAmount += out.amount;
-            }
-            outputCapacity = std::max(outputCapacity, 2 * totalAmount);
-        }
-    }
-
-    b.outputBuffer.items.clear();
-    b.outputBuffer.capacity = outputCapacity;
+    b.outputBuffer.caps.clear();
+    addOutputCaps(b.outputBuffer.caps, recipe);
 }
 
 void initShipyardBuffers(const GameConfig& config, Building& b)
 {
     b.inputBuffer.counts.clear();
     b.inputBuffer.caps.clear();
+    // A shipyard spawns a ship rather than producing items, so it holds no output
+    // buffer at all (REQ-MAT-OUTPUT-BUFFER, REQ-BLD-SHIPYARD).
     b.outputBuffer.items.clear();
-    b.outputBuffer.capacity = 0;
+    b.outputBuffer.caps.clear();
     const ShipDef* def = config.ships.findShipDef(b.recipeId);
     if (!def)
     {
@@ -133,11 +100,13 @@ void initShipyardBuffers(const GameConfig& config, Building& b)
 
 void initSalvageBayBuffer(const GameConfig& config, Building& b)
 {
-    // Salvage Bay has no recipe-driven buffer; its output-buffer holding size for
-    // ship drop-off is config-defined (REQ-BLD-SALVAGE-BAY).
+    // Salvage Bay has no recipe-driven buffer; scrap is the only thing it ever holds,
+    // and that single buffer's holding size for ship drop-off is config-defined
+    // (REQ-BLD-SALVAGE-BAY).
     b.outputBuffer.items.clear();
+    b.outputBuffer.caps.clear();
     const BuildingDef* def = config.buildings.findBuildingDef(BuildingType::SalvageBay);
-    b.outputBuffer.capacity =
+    b.outputBuffer.caps[ItemType{"scrap"}] =
         (def && def->outputBufferCapacity) ? *def->outputBufferCapacity : 0;
 }
 

src/lib/sim/BuildingBuffers.h

@@ -13,15 +13,11 @@
 // to BeltSystem. Free functions over the config and the building — they read no
 // factory state, so both BuildingSystem and ConstructionSystem can use them.
 
-// Buffers for a building running one known recipe: inputs capped at twice each
-// ingredient's per-cycle amount, output at twice the per-cycle total (one cycle's
-// max for a Reprocessing Plant, REQ-MAT-OUTPUT-BUFFER-REPROCESSING).
+// Buffers for a building running one known recipe: one buffer per material on each
+// side, capped at twice that material's per-cycle amount (REQ-MAT-INPUT-BUFFER,
+// REQ-MAT-OUTPUT-BUFFER).
 void initBuffers(Building& b, const RecipeDef& recipe);
 
-// Buffers for an auto-recipe building (Smelter, Reprocessing Plant), unioned over
-// every recipe of its type (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
-void initAutoBuffers(const GameConfig& config, Building& b);
-
 // Buffers for a shipyard: its schematic's materials plus those of every placed
 // module (REQ-BLD-SHIPYARD).
 void initShipyardBuffers(const GameConfig& config, Building& b);

src/lib/sim/BuildingSystem.cpp

@@ -48,29 +48,62 @@ BuildingSystem::BuildingSystem(const GameConfig& config,
 // ---------------------------------------------------------------------------
 
 
-std::vector<Item> BuildingSystem::rollReprocessingOutput(const RecipeDef& recipe)
+namespace
 {
-    std::vector<const RecipeOutput*> eligible;
-    std::vector<double> weights;
-    for (const RecipeOutput& out : recipe.outputs)
+// The items of one group, produced together (REQ-MAT-OUTPUT-GROUP).
+std::vector<Item> itemsOf(const RecipeOutputGroup& group)
+{
+    std::vector<Item> result;
+    for (const RecipeOutput& out : group.items)
     {
-        if (!m_isItemUnlocked(out.item)) { continue; }
-        eligible.push_back(&out);
-        weights.push_back(out.probability.value_or(1.0));
+        Item item;
+        item.type.id = out.item;
+        for (int i = 0; i < out.amount; ++i)
+        {
+            result.push_back(item);
+        }
+    }
+    return result;
+}
+}  // namespace
+
+std::vector<Item> BuildingSystem::rollOutputGroup(const RecipeDef& recipe)
+{
+    // One group: nothing to choose, so no weight is read, no draw is made, and no
+    // eligibility is tested (REQ-MAT-OUTPUT-GROUP, REQ-LOCK-OUTPUT-POOL).
+    //
+    // Not drawing matters beyond speed. A draw here would consume entropy for every
+    // ordinary recipe, shifting every later random outcome and invalidating recorded
+    // replays. And eligibility must not apply either: implicit unlocking is derived from
+    // demand, so an ordinary recipe's output can be perfectly producible while nothing
+    // yet calls for it -- testing it here would stop the building producing at all.
+    if (recipe.outputGroups.size() == 1)
+    {
+        return itemsOf(recipe.outputGroups.front());
+    }
+
+    // Several groups: only those whose items are all unlocked can be picked, and a group
+    // holding any locked item is dropped whole, since its items come together
+    // (REQ-LOCK-OUTPUT-POOL). Weights are renormalized over what is left by
+    // discrete_distribution.
+    std::vector<const RecipeOutputGroup*> eligible;
+    std::vector<double> weights;
+    for (const RecipeOutputGroup& group : recipe.outputGroups)
+    {
+        bool allUnlocked = true;
+        for (const RecipeOutput& out : group.items)
+        {
+            if (!m_isItemUnlocked(out.item)) { allUnlocked = false; break; }
+        }
+        if (!allUnlocked) { continue; }
+        eligible.push_back(&group);
+        weights.push_back(group.probability.value_or(1.0));
     }
 
     if (eligible.empty()) { return {}; }
 
     std::discrete_distribution<int> dist(weights.begin(), weights.end());
-    const RecipeOutput& chosen = *eligible[static_cast<std::size_t>(dist(m_rng))];
-    std::vector<Item> result;
-    Item item;
-    item.type.id = chosen.item;
-    for (int i = 0; i < chosen.amount; ++i)
-    {
-        result.push_back(item);
-    }
-    return result;
+    return itemsOf(*eligible[static_cast<std::size_t>(dist(m_rng))]);
 }
 
 // ---------------------------------------------------------------------------
@@ -200,12 +233,6 @@ void BuildingSystem::setRecipe(FactoryState& state, BuildingId id, const std::st
     {
         if (site.id == id)
         {
-            // Auto-recipe buildings have no player-selected recipe
-            // (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING); ignore any attempt to set one.
-            if (isAutoRecipeBuildingType(site.type))
-            {
-                return;
-            }
             // No-op if the recipe is unchanged, so a redundant selection does
             // not wipe an already-configured ship layout.
             if (site.recipeId == recipeId)
@@ -223,12 +250,6 @@ void BuildingSystem::setRecipe(FactoryState& state, BuildingId id, const std::st
     {
         if (building.id == id)
         {
-            // Auto-recipe buildings have no player-selected recipe
-            // (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING); ignore any attempt to set one.
-            if (isAutoRecipeBuildingType(building.type))
-            {
-                return;
-            }
             // No-op if the recipe is unchanged, so a redundant selection does
             // not wipe an already-configured ship layout or reset buffers.
             if (building.recipeId == recipeId)
@@ -240,7 +261,7 @@ void BuildingSystem::setRecipe(FactoryState& state, BuildingId id, const std::st
             building.inputBuffer.counts.clear();
             building.inputBuffer.caps.clear();
             building.outputBuffer.items.clear();
-            building.outputBuffer.capacity = 0;
+            building.outputBuffer.caps.clear();
             // Emerging items are part of the output buffer, so clearing it on a
             // recipe change discards them too (REQ-MAT-OUTPUT-EMERGE); in-transit
             // input items are discarded and their reservations released
@@ -307,7 +328,7 @@ void BuildingSystem::setShipLayout(FactoryState& state, BuildingId id, const Shi
             building.inputBuffer.counts.clear();
             building.inputBuffer.caps.clear();
             building.outputBuffer.items.clear();
-            building.outputBuffer.capacity = 0;
+            building.outputBuffer.caps.clear();
             for (std::vector<BeltItemSlot>& lane : building.emergingItems) { lane.clear(); }
             for (std::vector<BeltItemSlot>& lane : building.incomingItems) { lane.clear(); }
             if (!building.recipeId.empty() && building.type == BuildingType::Shipyard)
@@ -407,6 +428,10 @@ void BuildingSystem::tickBeltPull(FactoryState& state)
         {
             const std::optional<ItemType> peeked = m_belts.peekItem(building.inputPorts[i]);
             if (!peeked) { continue; }
+            // A Smelter or Reprocessing Plant without a recipe takes the first material
+            // offered to it as its selection (REQ-BLD-AUTO-RECIPE); the ports are walked
+            // in order, so which offer comes first is fixed.
+            selectAutoRecipeIfUnset(building, *peeked);
             if (!canAcceptInput(building, i, *peeked)) { continue; }
             const std::optional<Item> taken = m_belts.tryTakeItem(building.inputPorts[i]);
             if (taken)
@@ -417,6 +442,25 @@ void BuildingSystem::tickBeltPull(FactoryState& state)
     }
 }
 
+void BuildingSystem::selectAutoRecipeIfUnset(Building& building, const ItemType& offered)
+{
+    // Only while it holds none: once set, a recipe is the player's to change
+    // (REQ-BLD-AUTO-RECIPE). Buildings that select their own recipe are the only ones
+    // this applies to; everyone else ignores an offer they have no recipe for.
+    if (!building.recipeId.empty())
+    {
+        return;
+    }
+    const RecipeDef* recipe = findAutoRecipeFor(m_config, building.type, offered);
+    if (!recipe)
+    {
+        return;
+    }
+
+    building.recipeId = recipe->id;
+    initBuffers(building, *recipe);
+}
+
 bool BuildingSystem::canAcceptInput(const Building& consumer,
                                     std::size_t inputPortIndex,
                                     const ItemType& type) const
@@ -477,6 +521,10 @@ bool BuildingSystem::tryDirectCoupleDeposit(FactoryState& state, BuildingId prod
         if (in.direction != outputPort.direction) { continue; }
         if (inputBodyTile(in.tile, in.direction) != outputPort.tile) { continue; }
 
+        // A coupling is an offer too, so an unset auto-recipe building selects from it
+        // (REQ-BLD-AUTO-RECIPE). Without this a Smelter placed flush against a producer
+        // would accept nothing and leave it stuck at its port for good.
+        selectAutoRecipeIfUnset(*consumer, item.type);
         if (!canAcceptInput(*consumer, j, item.type)) { return false; }
         depositToInputBelt(*consumer, j, item);
         return true;
@@ -502,88 +550,78 @@ void BuildingSystem::tickProduction(FactoryState& state, Tick currentTick)
             continue;
         }
 
-        const bool autoRecipe = isAutoRecipeBuildingType(building.type);
-        if (!autoRecipe && building.recipeId.empty())
+        if (building.recipeId.empty())
         {
             continue;
         }
 
         // If a production cycle is active, check for completion. Completion only
         // needs the already-decided outputs, so it does not depend on which
-        // recipe is selected or auto-chosen.
+        // recipe is selected.
         if (building.production)
         {
-            if (currentTick >= building.production->completesAt)
+            if (currentTick < building.production->completesAt)
             {
-                for (const Item& item : building.production->chosenOutputs)
-                {
-                    building.outputBuffer.items.push_back(item);
-                }
-                building.production = std::nullopt;
+                continue;
             }
-            // Whether we just completed or are still running, do not start
-            // another cycle in the same tick.
+            for (const Item& item : building.production->chosenOutputs)
+            {
+                building.outputBuffer.items.push_back(item);
+            }
+            building.production = std::nullopt;
+            // Fall through to the start attempt below rather than idling for a tick,
+            // so a cycle takes exactly its recipe duration and a building fed to
+            // capacity produces at the configured rate (REQ-MAT-CYCLE). The start
+            // code runs once per building per tick, so at most one cycle begins here
+            // even when a duration rounds to zero ticks. The outputs just deposited
+            // count against the space check, so a cycle whose output no longer fits
+            // waits, exactly as it would have on the following tick.
+        }
+
+        // Idle: try to start the building's one selected recipe. Every type holds
+        // exactly one, a Smelter and a Reprocessing Plant included -- they differ only
+        // in how theirs first got set (REQ-BLD-AUTO-RECIPE).
+        const RecipeDef* recipe = getSelectedRecipe(m_config, building);
+        if (!recipe)
+        {
             continue;
         }
 
-        // Idle: gather the candidate recipes to try. Auto-recipe buildings
-        // (Smelter, Reprocessing Plant) have no selected recipe and try every
-        // recipe of their type in config order, running the first whose inputs
-        // are satisfied (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING). Other buildings
-        // try only their selected recipe.
-        const std::vector<const RecipeDef*> candidates =
-            gatherCandidateRecipes(m_config, building);
-
-        for (const RecipeDef* recipe : candidates)
+        // 1. All required inputs present?
+        if (!recipeInputsAvailable(building, *recipe))
         {
-            // 1. All required inputs present?
-            if (!recipeInputsAvailable(building, *recipe))
-            {
-                continue;
-            }
-
-            // 2. Determine chosen outputs (roll for reprocessing).
-            std::vector<Item> chosen;
-            if (building.type == BuildingType::ReprocessingPlant)
-            {
-                chosen = rollReprocessingOutput(*recipe);
-                if (chosen.empty()) { continue; }
-            }
-            else
-            {
-                for (const RecipeOutput& out : recipe->outputs)
-                {
-                    Item item;
-                    item.type.id = out.item;
-                    for (int i = 0; i < out.amount; ++i)
-                    {
-                        chosen.push_back(item);
-                    }
-                }
-            }
-
-            // 3. Output buffer has space for chosen outputs? Emerging items still
-            //    count against the buffer (REQ-MAT-OUTPUT-EMERGE).
-            const int newSize = building.getOutputItemCount()
-                              + static_cast<int>(chosen.size());
-            if (newSize > building.outputBuffer.capacity)
-            {
-                continue;
-            }
-
-            // 4. Consume inputs and start cycle.
-            for (const RecipeIngredient& ing : recipe->inputs)
-            {
-                building.inputBuffer.counts[ItemType{ing.item}] -= ing.amount;
-            }
-
-            Production prod;
-            prod.recipeId      = recipe->id;
-            prod.completesAt   = currentTick + secondsToTicks(recipe->durationSeconds);
-            prod.chosenOutputs = std::move(chosen);
-            building.production = std::move(prod);
-            break;  // At most one cycle starts per tick.
+            continue;
         }
+
+        // 2. Room for every output this cycle could produce -- checked before anything
+        //    is rolled (REQ-MAT-CYCLE). The roll below is committed the moment the cycle
+        //    starts, so a plant that could not store some outcome must not start at all:
+        //    that is what stops a stalled output belt from biasing the distribution
+        //    towards the outputs that still fit. Emerging items count against their
+        //    buffer (REQ-MAT-OUTPUT-EMERGE). The status light asks the same question to
+        //    decide yellow (REQ-UI-STATUS-LIGHT), so the test lives in one place.
+        if (!recipeOutputsFit(building, *recipe))
+        {
+            continue;
+        }
+
+        // 3. Settle what this cycle produces: its one output group, picked by weight only
+        //    where the recipe has several (REQ-MAT-OUTPUT-GROUP). Empty means every group
+        //    was ineligible, so there is nothing to run.
+        std::vector<Item> chosen = rollOutputGroup(*recipe);
+        if (chosen.empty()) { continue; }
+
+        // 4. Consume inputs and start cycle.
+        for (const RecipeIngredient& ing : recipe->inputs)
+        {
+            building.inputBuffer.counts[ItemType{ing.item}] -= ing.amount;
+        }
+
+        Production prod;
+        prod.recipeId      = recipe->id;
+        prod.completesAt   = currentTick + secondsToTicks(recipe->durationSeconds);
+        prod.chosenOutputs = std::move(chosen);
+        building.production = std::move(prod);
     }
 }
 
@@ -612,26 +650,29 @@ void BuildingSystem::tickShipyardProduction(FactoryState& state, Tick currentTic
         // If a cycle is in progress, check for completion.
         if (building.production)
         {
-            if (currentTick >= building.production->completesAt)
+            if (currentTick < building.production->completesAt)
             {
-                if (!building.outputPorts.empty())
-                {
-                    const Port& p = building.outputPorts[0];
-                    const QVector2D spawnPos(p.tile.x() + 0.5f, p.tile.y() + 0.5f);
-                    // A shipyard builds exactly what the player configured and
-                    // paid for. When no layout is set it produces a bare hull, so
-                    // pass an explicit empty layout rather than nullopt: the latter
-                    // would make ShipSystem fall back to the schematic's
-                    // defaultModules (a wave-only loadout) and yield free weapons.
-                    const std::optional<ShipLayoutConfig> layout =
-                        building.shipLayout.has_value()
-                            ? building.shipLayout
-                            : std::make_optional<ShipLayoutConfig>();
-                    m_spawnShip(building.recipeId, spawnPos, layout);
-                }
-                building.production = std::nullopt;
+                continue;
             }
-            continue;
+            if (!building.outputPorts.empty())
+            {
+                const Port& p = building.outputPorts[0];
+                const QVector2D spawnPos(p.tile.x() + 0.5f, p.tile.y() + 0.5f);
+                // A shipyard builds exactly what the player configured and
+                // paid for. When no layout is set it produces a bare hull, so
+                // pass an explicit empty layout rather than nullopt: the latter
+                // would make ShipSystem fall back to the schematic's
+                // defaultModules (a wave-only loadout) and yield free weapons.
+                const std::optional<ShipLayoutConfig> layout =
+                    building.shipLayout.has_value()
+                        ? building.shipLayout
+                        : std::make_optional<ShipLayoutConfig>();
+                m_spawnShip(building.recipeId, spawnPos, layout);
+            }
+            building.production = std::nullopt;
+            // Fall through and start the next cycle in this same tick, so a ship takes
+            // exactly its computed production time (REQ-BLD-SHIPYARD), as for the
+            // recipe buildings in tickProduction.
         }
 
         // Build combined materials list (base + modules).
@@ -942,21 +983,22 @@ void appendItems(Hasher& hasher, const std::vector<Item>& items)
     }
 }
 
+// std::map<ItemType, int> iterates in sorted-id order (ItemType::operator<), so both
+// buffer sides hash the same way in every run.
+void appendItemCounts(Hasher& hasher, const std::map<ItemType, int>& counts)
+{
+    hasher.append(counts.size());
+    for (const std::pair<const ItemType, int>& entry : counts)
+    {
+        hasher.append(entry.first.id);
+        hasher.append(entry.second);
+    }
+}
+
 void appendInputBuffer(Hasher& hasher, const InputBuffer& buffer)
 {
-    // std::map<ItemType, int> iterates in sorted-id order (ItemType::operator<).
-    hasher.append(buffer.counts.size());
-    for (const std::pair<const ItemType, int>& entry : buffer.counts)
-    {
-        hasher.append(entry.first.id);
-        hasher.append(entry.second);
-    }
-    hasher.append(buffer.caps.size());
-    for (const std::pair<const ItemType, int>& entry : buffer.caps)
-    {
-        hasher.append(entry.first.id);
-        hasher.append(entry.second);
-    }
+    appendItemCounts(hasher, buffer.counts);
+    appendItemCounts(hasher, buffer.caps);
 }
 }  // namespace
 
@@ -976,7 +1018,7 @@ void BuildingSystem::appendChecksum(const FactoryState& state, Hasher& hasher) c
         hasher.append(b.recipeId);
         appendInputBuffer(hasher, b.inputBuffer);
         appendItems(hasher, b.outputBuffer.items);
-        hasher.append(b.outputBuffer.capacity);
+        appendItemCounts(hasher, b.outputBuffer.caps);
         hasher.append(b.emergingItems.size());
         for (const std::vector<BeltItemSlot>& lane : b.emergingItems)
         {

src/lib/sim/BuildingSystem.h

@@ -188,6 +188,13 @@ private:
     // (on construction completion, or when un-queuing a deconstruction). No-op for
     // non-belt-subsystem types. Splitter filters are (re)applied after placement.
 
+    // Selects a recipe for an auto-recipe building that has none, from a material being
+    // offered to it at one of its input ports (REQ-BLD-AUTO-RECIPE). No-op for every
+    // other building, for one that already holds a recipe, and for a material none of
+    // its recipes consumes. Called from both intake paths -- the belt pull and the
+    // direct coupling -- since either can be where the first material arrives.
+    void                 selectAutoRecipeIfUnset(Building& building,
+                                                 const ItemType& offered);
     // True if the consumer would accept `type` at the given input port right now:
     // it is a required input (or a building block for the HQ), the reservation-aware
     // buffer has room, and the input belt entry is free (REQ-MAT-INPUT-INTAKE).
@@ -217,11 +224,11 @@ private:
     // (ignoring output-buffer space); drives the Starved/Blocked distinction of
     // the status light (REQ-UI-STATUS-LIGHT).
 
-    // Buffers for an auto-recipe building (Smelter, Reprocessing Plant): input
-    // caps span the union of every recipe of the building's type; no player
-    // recipe is selected (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
-    // Core input-edge scan shared by operational buildings and construction sites.
-    std::vector<Item>   rollReprocessingOutput(const RecipeDef& recipe);
+    // What one cycle of this recipe produces: the items of its one output group
+    // (REQ-MAT-OUTPUT-GROUP). Where the recipe has several, one is picked by weight from
+    // those currently eligible (REQ-LOCK-OUTPUT-POOL) and the result is empty if none is;
+    // where it has one, that group is returned with no draw and no eligibility test.
+    std::vector<Item>   rollOutputGroup(const RecipeDef& recipe);
 
     const GameConfig&                              m_config;
 

src/lib/sim/ConstructionSystem.cpp

@@ -67,12 +67,6 @@ void ConstructionSystem::tick(FactoryState& state, BeltSystem& belts, Tick curre
     {
         initSalvageBayBuffer(m_config, building);
     }
-    else if (isAutoRecipeBuildingType(building.type))
-    {
-        // Smelter/Reprocessing Plant need no recipe selection; buffers are set
-        // up from all recipes of the type (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
-        initAutoBuffers(m_config, building);
-    }
     else if (!building.recipeId.empty())
     {
         if (building.type == BuildingType::Shipyard)

src/lib/sim/EntityHitTest.cpp

@@ -4,6 +4,7 @@
 #include <cmath>
 
 #include "EntityAdmin.h"
+#include "SelectionBox.h"
 #include "PositionComponent.h"
 #include "DebrisComponent.h"
 #include "ShipIdentityComponent.h"
@@ -82,45 +83,29 @@ entt::entity debrisAtWorldPos(EntityAdmin& admin, QVector2D worldPos)
     return bestDebris;
 }
 
-std::vector<entt::entity> debrisInBox(EntityAdmin& admin, QPoint tileA, QPoint tileB)
+std::vector<entt::entity> debrisInBox(EntityAdmin& admin, const QRectF& worldBox)
 {
-    const int minX = std::min(tileA.x(), tileB.x());
-    const int maxX = std::max(tileA.x(), tileB.x());
-    const int minY = std::min(tileA.y(), tileB.y());
-    const int maxY = std::max(tileA.y(), tileB.y());
-
     std::vector<entt::entity> result;
     admin.forEach<DebrisComponent, PositionComponent>(
         [&](entt::entity entity, const DebrisComponent& /*sd*/, const PositionComponent& pos)
         {
-            const int tileX = static_cast<int>(std::floor(pos.value.x()));
-            const int tileY = static_cast<int>(std::floor(pos.value.y()));
-            if (tileX >= minX && tileX <= maxX && tileY >= minY && tileY <= maxY)
-            {
-                result.push_back(entity);
-            }
+            if (boxCoversPoint(worldBox, pos.value)) { result.push_back(entity); }
         });
     return result;
 }
 
-std::vector<entt::entity> actorsInBox(EntityAdmin& admin, QPoint tileA, QPoint tileB)
+std::vector<entt::entity> actorsInBox(EntityAdmin& admin, const QRectF& worldBox)
 {
-    const int minX = std::min(tileA.x(), tileB.x());
-    const int maxX = std::max(tileA.x(), tileB.x());
-    const int minY = std::min(tileA.y(), tileB.y());
-    const int maxY = std::max(tileA.y(), tileB.y());
-
     std::vector<entt::entity> result;
 
-    // Stations: included when any occupied body cell lies in the box.
+    // Stations occupy whole tiles: included when the box overlaps any occupied cell.
     admin.forEach<StationBodyComponent, HealthComponent>(
         [&](entt::entity entity, const StationBodyComponent& sb, const HealthComponent& h)
         {
             if (h.hp <= 0.0f) { return; }
             for (const QPoint& cell : sb.bodyCells)
             {
-                if (cell.x() >= minX && cell.x() <= maxX
-                    && cell.y() >= minY && cell.y() <= maxY)
+                if (boxCoversTile(worldBox, cell))
                 {
                     result.push_back(entity);
                     return;
@@ -128,19 +113,15 @@ std::vector<entt::entity> actorsInBox(EntityAdmin& admin, QPoint tileA, QPoint t
             }
         });
 
-    // Ships: included when the floored position tile lies in the box. Requiring
-    // ShipIdentityComponent excludes the HQ proxy and any station bodies.
+    // Ships have a position rather than a footprint: included when the box contains
+    // that position. Requiring ShipIdentityComponent excludes the HQ proxy and any
+    // station bodies.
     admin.forEach<ShipIdentityComponent, PositionComponent, HealthComponent>(
         [&](entt::entity entity, const ShipIdentityComponent& /*id*/,
             const PositionComponent& pos, const HealthComponent& h)
         {
             if (h.hp <= 0.0f) { return; }
-            const int tileX = static_cast<int>(std::floor(pos.value.x()));
-            const int tileY = static_cast<int>(std::floor(pos.value.y()));
-            if (tileX >= minX && tileX <= maxX && tileY >= minY && tileY <= maxY)
-            {
-                result.push_back(entity);
-            }
+            if (boxCoversPoint(worldBox, pos.value)) { result.push_back(entity); }
         });
 
     return result;

src/lib/sim/EntityHitTest.h

@@ -3,6 +3,7 @@
 #include <vector>
 
 #include <QPoint>
+#include <QRectF>
 #include <QVector2D>
 
 #include "entt/entity/entity.hpp"
@@ -16,13 +17,13 @@ entt::entity entityAtWorldPos(EntityAdmin& admin, QVector2D worldPos);
 // after actors: entityAtWorldPos never returns debris (debris has no HealthComponent).
 entt::entity debrisAtWorldPos(EntityAdmin& admin, QVector2D worldPos);
 
-// Returns every piece of debris whose position falls within the inclusive tile rectangle
-// spanned by tileA and tileB, in any corner order (REQ-UI-DEBRIS-MULTI-SELECT).
-std::vector<entt::entity> debrisInBox(EntityAdmin& admin, QPoint tileA, QPoint tileB);
+// Returns every piece of debris the selection box covers — that is, whose position it
+// contains, per boxCoversPoint (REQ-UI-DEBRIS-MULTI-SELECT). `worldBox` is in world
+// coordinates and normalized; it is not snapped to tiles.
+std::vector<entt::entity> debrisInBox(EntityAdmin& admin, const QRectF& worldBox);
 
-// Returns every living actor (ship or defence station, player or enemy) that falls
-// within the inclusive tile rectangle spanned by tileA and tileB, in any corner order
-// (REQ-UI-MULTI-SELECT, REQ-UI-ENTITY-CLICK-SELECT). A ship is included when its floored
-// position tile lies in the box; a station is included when any of its body cells does.
-// Dead actors (hp <= 0) and the HQ proxy are excluded.
-std::vector<entt::entity> actorsInBox(EntityAdmin& admin, QPoint tileA, QPoint tileB);
+// Returns every living actor (ship or defence station, player or enemy) the selection
+// box covers (REQ-UI-MULTI-SELECT, REQ-UI-ENTITY-CLICK-SELECT): a ship when the box
+// contains its position, a station when the box overlaps any of its body cells — the
+// two rules of SelectionBox.h. Dead actors (hp <= 0) and the HQ proxy are excluded.
+std::vector<entt::entity> actorsInBox(EntityAdmin& admin, const QRectF& worldBox);

src/lib/sim/FactoryQueries.cpp

@@ -4,6 +4,8 @@
 #include <limits>
 
 #include "PortGeometry.h"
+#include "ProductionRules.h"
+#include "SelectionBox.h"
 #include "SurfaceMask.h"
 
 #include "Item.h"
@@ -122,12 +124,14 @@ bool deliverScrapToSalvageBay(FactoryState& state, BuildingId bayId)
         return false;  // queued for deconstruction: stopped operating (REQ-BLD-DECON-QUEUE)
     }
     // Emerging scrap still counts against the bay's holding capacity
-    // (REQ-MAT-OUTPUT-EMERGE).
-    if (bay->getOutputItemCount() >= bay->outputBuffer.capacity)
+    // (REQ-MAT-OUTPUT-EMERGE). Scrap is all the bay ever holds, so its single buffer is
+    // the one being filled (REQ-BLD-SALVAGE-BAY).
+    const ItemType scrap{"scrap"};
+    if (!outputBufferHasRoom(*bay, scrap, 1))
     {
         return false;
     }
-    bay->outputBuffer.items.push_back(Item{ItemType{"scrap"}});
+    bay->outputBuffer.items.push_back(Item{scrap});
     return true;
 }
 
@@ -182,22 +186,13 @@ getSiteSplitterInfo(const FactoryState& state, const GameConfig& config, Buildin
 
 
 std::vector<BuildingId> buildingsInBox(const FactoryState& state,
-                                       QPoint cornerA, QPoint cornerB)
+                                       const QRectF& worldBox)
 {
-    const int x0 = std::min(cornerA.x(), cornerB.x());
-    const int y0 = std::min(cornerA.y(), cornerB.y());
-    const int x1 = std::max(cornerA.x(), cornerB.x());
-    const int y1 = std::max(cornerA.y(), cornerB.y());
-
     const auto covers = [&](const std::vector<QPoint>& bodyCells)
     {
         for (const QPoint& cell : bodyCells)
         {
-            if (cell.x() >= x0 && cell.x() <= x1
-             && cell.y() >= y0 && cell.y() <= y1)
-            {
-                return true;
-            }
+            if (boxCoversTile(worldBox, cell)) { return true; }
         }
         return false;
     };

src/lib/sim/FactoryQueries.h

@@ -3,6 +3,7 @@
 #include <vector>
 
 #include <QPoint>
+#include <QRectF>
 #include <QVector2D>
 
 #include "Building.h"
@@ -71,11 +72,12 @@ std::optional<BeltSystem::SplitterInfo> getSiteSplitterInfo(const FactoryState&
                                                             const GameConfig& config,
                                                             BuildingId id);
 
-// Ids of all buildings and construction sites whose footprint intersects the tile
-// box spanned by the two (unordered) corner tiles (REQ-UI-MULTI-SELECT,
-// REQ-BLD-DECONSTRUCT-BOX).
+// Ids of all buildings and construction sites the selection box covers — those with
+// a body cell the box overlaps, per boxCoversTile (REQ-UI-MULTI-SELECT,
+// REQ-BLD-DECONSTRUCT-BOX). `worldBox` is in world coordinates and normalized; it is
+// not snapped to tiles.
 std::vector<BuildingId> buildingsInBox(const FactoryState& state,
-                                       QPoint cornerA, QPoint cornerB);
+                                       const QRectF& worldBox);
 
 // Every tunnel entry and exit, built or still a construction site, indexed by its
 // single-cell tile. Shared by the placement preview and the selection highlight.

src/lib/sim/ProductionRules.cpp

@@ -1,33 +1,44 @@
 #include "ProductionRules.h"
 
+#include <algorithm>
+#include <map>
+
 #include "BuildingType.h"
 #include "ItemType.h"
 #include "ModulesConfig.h"
 #include "ShipsConfig.h"
 
-std::vector<const RecipeDef*>
-gatherCandidateRecipes(const GameConfig& config, const Building& b)
+const RecipeDef* getSelectedRecipe(const GameConfig& config, const Building& b)
 {
-    std::vector<const RecipeDef*> candidates;
-    if (isAutoRecipeBuildingType(b.type))
+    if (b.recipeId.empty())
     {
-        for (const RecipeDef& r : config.recipes.recipes)
+        return nullptr;
+    }
+    return config.recipes.findRecipeDef(b.recipeId, b.type);
+}
+
+const RecipeDef* findAutoRecipeFor(const GameConfig& config, BuildingType type,
+                                   const ItemType& item)
+{
+    if (!isAutoRecipeBuildingType(type))
+    {
+        return nullptr;
+    }
+
+    // Config order decides where a material feeds more than one recipe of the type, so
+    // the same offer always picks the same recipe (REQ-BLD-AUTO-RECIPE).
+    for (const RecipeDef& recipe : config.recipes.recipes)
+    {
+        if (recipe.building != type) { continue; }
+        for (const RecipeIngredient& ing : recipe.inputs)
         {
-            if (r.building == b.type && !r.inputs.empty())
+            if (ItemType{ing.item} == item)
             {
-                candidates.push_back(&r);
+                return &recipe;
             }
         }
     }
-    else
-    {
-        const RecipeDef* recipe = config.recipes.findRecipeDef(b.recipeId, b.type);
-        if (recipe)
-        {
-            candidates.push_back(recipe);
-        }
-    }
-    return candidates;
+    return nullptr;
 }
 bool recipeInputsAvailable(const Building& b, const RecipeDef& recipe)
 {
@@ -45,9 +56,17 @@ bool recipeInputsAvailable(const Building& b, const RecipeDef& recipe)
 }
 std::map<std::string, int>
 computeShipyardRequiredMaterials(const GameConfig& config, const Building& b)
+{
+    return computeShipyardRequiredMaterials(config, b.recipeId, b.shipLayout);
+}
+
+std::map<std::string, int>
+computeShipyardRequiredMaterials(const GameConfig& config,
+                                 const std::string& recipeId,
+                                 const std::optional<ShipLayoutConfig>& shipLayout)
 {
     std::map<std::string, int> requiredMaterials;
-    const ShipDef* shipDef = config.ships.findShipDef(b.recipeId);
+    const ShipDef* shipDef = config.ships.findShipDef(recipeId);
     if (!shipDef)
     {
         return requiredMaterials;
@@ -56,9 +75,9 @@ computeShipyardRequiredMaterials(const GameConfig& config, const Building& b)
     {
         requiredMaterials[ing.item] += ing.amount;
     }
-    if (b.shipLayout.has_value())
+    if (shipLayout.has_value())
     {
-        for (const PlacedModule& pm : b.shipLayout->placedModules)
+        for (const PlacedModule& pm : shipLayout->placedModules)
         {
             const ModuleDef* modDef = config.modules.findModuleDef(pm.moduleId);
             if (!modDef)
@@ -73,6 +92,33 @@ computeShipyardRequiredMaterials(const GameConfig& config, const Building& b)
     }
     return requiredMaterials;
 }
+
+double computeShipyardProductionTimeSeconds(
+    const GameConfig& config, const std::string& recipeId,
+    const std::optional<ShipLayoutConfig>& shipLayout)
+{
+    const ShipDef* shipDef = config.ships.findShipDef(recipeId);
+    if (!shipDef)
+    {
+        return 0.0;
+    }
+
+    double seconds = shipDef->schematic.productionTimeSeconds;
+    if (shipLayout.has_value())
+    {
+        for (const PlacedModule& pm : shipLayout->placedModules)
+        {
+            const ModuleDef* modDef = config.modules.findModuleDef(pm.moduleId);
+            if (!modDef)
+            {
+                continue;
+            }
+            seconds += modDef->productionTimeSeconds;
+        }
+    }
+    return seconds;
+}
+
 bool hasInputsToStart(const GameConfig& config, const Building& b)
 {
     if (b.type == BuildingType::Shipyard)
@@ -92,18 +138,56 @@ bool hasInputsToStart(const GameConfig& config, const Building& b)
         return true;
     }
 
-    // Recipe buildings: startable if any candidate recipe's inputs are satisfied.
-    // A Miner recipe has no inputs, so an idle Miner is always startable and its
-    // only idle reason is a full output buffer.
-    for (const RecipeDef* recipe : gatherCandidateRecipes(config, b))
+    // Recipe buildings: startable if the selected recipe's inputs are satisfied. A Miner
+    // recipe has no inputs, so an idle Miner is always startable here and its only idle
+    // reason is an output buffer without room for the next cycle.
+    const RecipeDef* recipe = getSelectedRecipe(config, b);
+    return recipe != nullptr && recipeInputsAvailable(b, *recipe);
+}
+
+bool outputBufferHasRoom(const Building& b, const ItemType& type, int itemCount)
+{
+    const std::map<ItemType, int>::const_iterator capIt = b.outputBuffer.caps.find(type);
+    const int cap = (capIt != b.outputBuffer.caps.end()) ? capIt->second : 0;
+    return b.getOutputItemCount(type) + itemCount <= cap;
+}
+
+bool recipeOutputsFit(const Building& b, const RecipeDef& recipe)
+{
+    for (const RecipeOutputGroup& group : recipe.outputGroups)
     {
-        if (recipeInputsAvailable(b, *recipe))
+        // A group's items come together, so an item listed twice in one is produced in the
+        // sum of those amounts and judged once, as a sum.
+        std::map<ItemType, int> perCycle;
+        for (const RecipeOutput& out : group.items)
         {
-            return true;
+            perCycle[ItemType{out.item}] += out.amount;
+        }
+        for (const std::pair<const ItemType, int>& entry : perCycle)
+        {
+            if (!outputBufferHasRoom(b, entry.first, entry.second))
+            {
+                return false;
+            }
         }
     }
-    return false;
+    return true;
 }
+
+bool canStartCycle(const GameConfig& config, const Building& b)
+{
+    // A shipyard's completed cycle spawns a ship instead of filling an output buffer
+    // (REQ-BLD-SHIPYARD), so holding the materials is the whole condition.
+    if (b.type == BuildingType::Shipyard)
+    {
+        return hasInputsToStart(config, b);
+    }
+
+    const RecipeDef* recipe = getSelectedRecipe(config, b);
+    return recipe != nullptr && recipeInputsAvailable(b, *recipe)
+           && recipeOutputsFit(b, *recipe);
+}
+
 std::optional<ProductionStatus>
 getProductionStatus(const GameConfig& config, const Building& building)
 {
@@ -122,9 +206,10 @@ getProductionStatus(const GameConfig& config, const Building& building)
         return std::nullopt;
     }
 
-    // Grey only applies to player-configured types; auto-recipe buildings
-    // (Smelter, Reprocessing Plant) always run an implicit recipe.
-    if (!isAutoRecipeBuildingType(building.type) && building.recipeId.empty())
+    // Every production building can be unconfigured, an auto-recipe building included:
+    // it holds no recipe until one is offered to it, and the player can hand it back to
+    // automatic selection (REQ-BLD-AUTO-RECIPE, REQ-UI-STATUS-LIGHT).
+    if (building.recipeId.empty())
     {
         return ProductionStatus::Unconfigured;
     }
@@ -134,9 +219,18 @@ getProductionStatus(const GameConfig& config, const Building& building)
         return ProductionStatus::Producing;
     }
 
-    // Idle: missing inputs (red) take precedence over a full output buffer
-    // (yellow). If inputs are present yet the building is idle, the only remaining
-    // reason it could not start a cycle is a full output buffer (REQ-MAT-CYCLE).
+    // Idle, but blocked by neither condition: the building is only between cycles and
+    // the simulation starts the next one on a following tick. A building running back
+    // to back sits here for exactly one tick per cycle, since tickProduction never
+    // starts a cycle in the tick one completed, so this must read as producing rather
+    // than blink (REQ-UI-STATUS-LIGHT, REQ-MAT-CYCLE).
+    if (canStartCycle(config, building))
+    {
+        return ProductionStatus::Producing;
+    }
+
+    // Idle for a reason: a missing input (red) takes precedence over an output buffer
+    // with no room for the next cycle's output (yellow).
     return hasInputsToStart(config, building) ? ProductionStatus::Blocked
-                                      : ProductionStatus::Starved;
+                                              : ProductionStatus::Starved;
 }

src/lib/sim/ProductionRules.h

@@ -25,10 +25,16 @@ enum class ProductionStatus
 // Pure functions of the config and the building itself — they read no factory
 // state, so they are free functions rather than BuildingSystem members.
 
-// Recipes this building could run: every recipe of its type for an auto-recipe
-// building (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING), otherwise just its selected one.
-std::vector<const RecipeDef*> gatherCandidateRecipes(const GameConfig& config,
-                                                     const Building& b);
+// The recipe this building runs, or null when it has none selected. Every building type
+// holds exactly one, a Smelter and a Reprocessing Plant included -- they only differ in
+// how theirs first gets set (REQ-BLD-AUTO-RECIPE).
+const RecipeDef* getSelectedRecipe(const GameConfig& config, const Building& b);
+
+// The recipe an auto-recipe building adopts when this material is offered to it while it
+// has none: the first recipe of its type, in config order, that consumes the material
+// (REQ-BLD-AUTO-RECIPE). Null when no recipe of the type takes it.
+const RecipeDef* findAutoRecipeFor(const GameConfig& config, BuildingType type,
+                                   const ItemType& item);
 
 // True when the building's input buffer holds every ingredient the recipe needs.
 bool recipeInputsAvailable(const Building& b, const RecipeDef& recipe);
@@ -38,9 +44,38 @@ bool recipeInputsAvailable(const Building& b, const RecipeDef& recipe);
 std::map<std::string, int> computeShipyardRequiredMaterials(const GameConfig& config,
                                                             const Building& b);
 
+// The same sum over a stored configuration rather than an operational building, so a
+// construction site's schematic can be costed before it is built (REQ-BLD-SITE-CONFIG).
+std::map<std::string, int> computeShipyardRequiredMaterials(
+    const GameConfig& config, const std::string& recipeId,
+    const std::optional<ShipLayoutConfig>& shipLayout);
+
+// The ship's base production time plus that of every module in the configured layout
+// (REQ-MOD-PRODUCTION-TIME), over a stored configuration as above.
+double computeShipyardProductionTimeSeconds(
+    const GameConfig& config, const std::string& recipeId,
+    const std::optional<ShipLayoutConfig>& shipLayout);
+
 // True when a production cycle could start right now, ignoring output-buffer space.
 bool hasInputsToStart(const GameConfig& config, const Building& b);
 
+// True when the building can take `itemCount` more items of `type` beside what it
+// already holds of it. An emerging item has not left the building yet and so still
+// counts against that material's capacity (REQ-MAT-OUTPUT-EMERGE, REQ-MAT-OUTPUT-BUFFER).
+bool outputBufferHasRoom(const Building& b, const ItemType& type, int itemCount);
+
+// True when every one of the recipe's output groups would fit -- the gate a cycle has to
+// pass before it may start (REQ-MAT-CYCLE, REQ-MAT-OUTPUT-GROUP). With a single group that
+// is simply that group. With several the pick is committed the moment the cycle starts, so
+// every outcome must fit: testing all of them rather than the picked one is what keeps a
+// stalled output belt from biasing the distribution.
+bool recipeOutputsFit(const Building& b, const RecipeDef& recipe);
+
+// True when a production cycle could actually start right now: some candidate recipe
+// has its inputs *and* passes recipeOutputsFit (REQ-MAT-CYCLE). Stricter than
+// hasInputsToStart, which looks at the input buffers alone.
+bool canStartCycle(const GameConfig& config, const Building& b);
+
 // Status light for a building, or nullopt for types that show none — belts,
 // splitters, tunnels, HQ and defence stations (REQ-UI-STATUS-LIGHT).
 std::optional<ProductionStatus> getProductionStatus(const GameConfig& config,

src/lib/sim/ThreatCostCalculator.cpp

@@ -97,35 +97,42 @@ ThreatCostTable computeThreatCostTable(const GameConfig& config)
     // values are raw from config; we normalize them per-recipe below).
     std::map<std::string, std::vector<RecipeRef>> reprocessingRecipes;
 
+    // What decides which model an item's threat follows is the recipe's shape, not the
+    // building running it (REQ-MAT-OUTPUT-GROUP): a recipe with several groups yields one
+    // of them by chance, so its items cost the cycle divided by their odds; a recipe with
+    // one group yields it every cycle, so its items cost the cycle outright.
     for (const RecipeDef& recipe : config.recipes.recipes)
     {
-        if (recipe.building == BuildingType::ReprocessingPlant)
+        if (recipe.outputGroups.size() > 1)
         {
-            // Compute the total weight across all outputs of this reprocessing recipe
-            // so we can normalize each output's probability.
+            // Total weight across the groups, so each group's probability normalizes.
             double totalWeight = 0.0;
-            for (const RecipeOutput& out : recipe.outputs)
+            for (const RecipeOutputGroup& group : recipe.outputGroups)
             {
-                totalWeight += out.probability.value_or(1.0);
+                totalWeight += group.probability.value_or(1.0);
             }
             if (totalWeight <= 0.0)
             {
                 continue;
             }
 
-            for (const RecipeOutput& out : recipe.outputs)
+            for (const RecipeOutputGroup& group : recipe.outputGroups)
             {
-                RecipeRef ref;
-                ref.recipe = &recipe;
-                ref.outputItem = out.item;
-                ref.outputAmount = out.amount;
-                ref.probability = out.probability.value_or(1.0) / totalWeight;
-                reprocessingRecipes[out.item].push_back(ref);
+                const double probability = group.probability.value_or(1.0) / totalWeight;
+                for (const RecipeOutput& out : group.items)
+                {
+                    RecipeRef ref;
+                    ref.recipe = &recipe;
+                    ref.outputItem = out.item;
+                    ref.outputAmount = out.amount;
+                    ref.probability = probability;
+                    reprocessingRecipes[out.item].push_back(ref);
+                }
             }
         }
         else
         {
-            // Check whether this non-reprocessing recipe consumes scrap.
+            // Check whether this single-group recipe consumes scrap.
             bool consumesScrap = false;
             for (const RecipeIngredient& input : recipe.inputs)
             {
@@ -136,7 +143,7 @@ ThreatCostTable computeThreatCostTable(const GameConfig& config)
                 }
             }
 
-            for (const RecipeOutput& out : recipe.outputs)
+            for (const RecipeOutput& out : recipe.outputGroups.front().items)
             {
                 if (!consumesScrap)
                 {
@@ -288,8 +295,13 @@ ThreatCostTable computeThreatCostTable(const GameConfig& config)
                     scrapPerCycle += input.amount;
                 }
 
+                // Per unit: the cycle's cost, divided by the odds of getting this group
+                // at all and then by how many units that group yields (REQ-THREAT-ITEM).
+                const double perUnitDivisor =
+                    ref.probability * static_cast<double>(ref.outputAmount);
+                if (perUnitDivisor <= 0.0) { continue; }
                 double threat = (table.scrapThreat * scrapPerCycle
-                                 + ref.recipe->durationSeconds) / ref.probability;
+                                 + ref.recipe->durationSeconds) / perUnitDivisor;
 
                 std::map<std::string, double>::iterator existing = resolved.find(item);
                 if (existing == resolved.end() || threat > existing->second)

src/lib/sim/UnlockState.cpp

@@ -244,9 +244,9 @@ UnlockState::UnlockedSets UnlockState::computeUnlockedSets(
         if (def.building == BuildingType::Assembler
             && (def.unlockedAtStart || unlockedRecipeSchematicIds.count(def.id) > 0))
         {
-            for (const RecipeOutput& out : def.outputs)
+            for (const std::string& item : getProducibleItems(def))
             {
-                result.itemIds.insert(out.item);
+                result.itemIds.insert(item);
             }
         }
     }
@@ -272,9 +272,9 @@ UnlockState::UnlockedSets UnlockState::computeUnlockedSets(
                 continue;
             }
             bool producesUnlocked = false;
-            for (const RecipeOutput& out : recipe.outputs)
+            for (const std::string& item : getProducibleItems(recipe))
             {
-                if (result.itemIds.count(out.item) > 0)
+                if (result.itemIds.count(item) > 0)
                 {
                     producesUnlocked = true;
                     break;

src/test/BehaviorSystemTest.cpp

@@ -1000,8 +1000,9 @@ TEST_CASE("SalvagerSystem: full-cargo ship at its SalvageBay hands over cargo",
     }
     const Building* bay = findBuilding(f.state, bayId);
     REQUIRE(bay != nullptr);
-    // Config-driven output-buffer capacity is applied on placement (REQ-BLD-SALVAGE-BAY).
-    REQUIRE(bay->outputBuffer.capacity == 20);
+    // Config-driven output-buffer capacity is applied on placement, onto the single
+    // scrap buffer the bay holds (REQ-BLD-SALVAGE-BAY).
+    REQUIRE(bay->outputBuffer.caps.at(ItemType{"scrap"}) == 20);
 
     const QVector2D bayCenter(bay->anchor.x() + bay->footprint.width()  / 2.0f,
                               bay->anchor.y() + bay->footprint.height() / 2.0f);

src/test/BuildModeControllerTest.cpp

@@ -288,6 +288,66 @@ TEST_CASE("The effective builder type follows the resolved tunnel end", "[buildm
     REQUIRE(controller.getTunnelPartnerTile() == QPoint(5, 5));
 }
 
+TEST_CASE("Clearing the hover drops everything the cursor pointed at", "[buildmode]")
+{
+    // A cursor that leaves the world hovers nothing, so the ghost and its resolved
+    // tunnel end go with it, while the mode itself stays active (REQ-BLD-GHOST).
+    BuildModeController controller;
+    controller.enterBuilderMode(BuildingType::TunnelEntry);
+    controller.setGhostTile(QPoint(7, 2));
+    controller.setGhostValidity(true);
+    controller.setTunnelGhost(BuildingType::TunnelExit, QPoint(5, 2));
+
+    controller.clearHover();
+
+    REQUIRE(controller.isBuilderMode());
+    REQUIRE_FALSE(controller.getGhostTile().has_value());
+    REQUIRE_FALSE(controller.isGhostValid());
+    REQUIRE(controller.getEffectiveBuilderType() == BuildingType::TunnelEntry);
+    REQUIRE_FALSE(controller.getTunnelPartnerTile().has_value());
+}
+
+TEST_CASE("Clearing the hover keeps a belt drag's path", "[buildmode]")
+{
+    // A drag holds the button and goes on hovering wherever the cursor travels, so
+    // nothing clears it short of releasing or cancelling (REQ-BLD-BELT-DRAG).
+    BuildModeController controller;
+    controller.enterBuilderMode(BuildingType::Belt);
+    controller.beginBeltDrag(QPoint(3, 4));
+    controller.setBeltDragPath({BeltPathTile{QPoint(3, 4), Rotation::East}});
+
+    controller.clearHover();
+
+    REQUIRE(controller.isDraggingBelt());
+    REQUIRE(controller.getBeltDragPath().size() == 1);
+}
+
+TEST_CASE("Clearing the hover drops the blueprint ghost and its transfer", "[buildmode]")
+{
+    BuildModeController controller;
+    controller.enterBlueprintMode(makeBlueprint());
+    controller.setBlueprintGhostTile(QPoint(9, 9));
+    controller.setHoveredGhostTransfer(true);
+
+    controller.clearHover();
+
+    REQUIRE(controller.isBlueprintMode());
+    REQUIRE_FALSE(controller.getBlueprintGhostTile().has_value());
+    REQUIRE_FALSE(controller.isHoveredGhostTransfer());
+}
+
+TEST_CASE("Clearing the hover drops the deconstruct hover", "[buildmode]")
+{
+    BuildModeController controller;
+    controller.toggleDeconstructMode();
+    controller.setDeconstructHoverBuildingId(BuildingId(4));
+
+    controller.clearHover();
+
+    REQUIRE(controller.isDeconstructMode());
+    REQUIRE_FALSE(controller.getDeconstructHoverBuildingId().has_value());
+}
+
 TEST_CASE("A non-tunnel builder ignores any resolved tunnel end", "[buildmode]")
 {
     BuildModeController controller;

src/test/BuildingTest.cpp

@@ -11,9 +11,11 @@
 #include <vector>
 
 #include <QPoint>
+#include <QRectF>
 
 #include "BeltSystem.h"
 #include "Building.h"
+#include "BuildingBuffers.h"
 #include "BuildingSystem.h"
 #include "ConstructionSystem.h"
 #include "DeconstructionSystem.h"
@@ -102,14 +104,20 @@ struct PlacementFixture
     BuildingSystem bs;
 
     // Defaults to the configured belt speed; pass kFastBeltSpeed_tps where the test
-    // needs items to arrive immediately.
-    explicit PlacementFixture(std::optional<double> beltSpeed_tps = std::nullopt)
+    // needs items to arrive immediately. Everything counts as unlocked unless the test
+    // says otherwise, which is what the output-group eligibility rule turns on
+    // (REQ-LOCK-OUTPUT-POOL).
+    explicit PlacementFixture(
+        std::optional<double> beltSpeed_tps = std::nullopt,
+        std::function<bool(const std::string&)> isItemUnlocked = nullptr)
         : belts(beltSpeed_tps.value_or(cfg.world.beltSpeed_tps))
         , bs(cfg, belts,
              [this]() { return nextBuildingId++; },
              [this](int n) { stock += n; },
              [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
-             [](const std::string&) -> bool { return true; },
+             isItemUnlocked ? std::move(isItemUnlocked)
+                            : std::function<bool(const std::string&)>(
+                                  [](const std::string&) { return true; }),
              rng)
     {
     }
@@ -134,6 +142,26 @@ TEST_CASE("BuildingSystem: place miner occupies expected body tiles", "[building
     REQUIRE_FALSE(isTileOccupied(f.state, QPoint(1, 1)));
 }
 
+TEST_CASE("buildingsInBox covers a body cell the box only reaches into", "[building]")
+{
+    PlacementFixture f;
+
+    const BuildingId id = f.bs.place(f.state, BuildingType::Miner, QPoint(0, 0),
+                                     Rotation::East, 0).value();
+
+    // Body at (0,0),(1,0),(0,1). The box is unsnapped and lies wholly within cell
+    // (1,0) without filling it, which is enough: a building is covered when the box
+    // overlaps any of its body cells (REQ-UI-MULTI-SELECT, Coverage).
+    const std::vector<BuildingId> grazed =
+        buildingsInBox(f.state, QRectF(1.6, 0.4, 0.2, 0.2));
+    REQUIRE(grazed.size() == 1);
+    REQUIRE(grazed.front() == id);
+
+    // (1,1) is the output-port tile, not a body cell, so a box inside it covers
+    // nothing even though it is surrounded by the miner's cells.
+    REQUIRE(buildingsInBox(f.state, QRectF(1.2, 1.2, 0.5, 0.5)).empty());
+}
+
 // -- World-bounds rejection (REQ-BLD-PLACE-VALID) ---------------------------
 
 TEST_CASE("BuildingSystem: place rejects a building above the world (y < 0)", "[building]")
@@ -495,13 +523,13 @@ TEST_CASE("BuildingSystem: miner output buffer stalls when full", "[building]")
 
     Tick tick = 0;
     // Construction (10s) then cycle 1 starts at tick 300 (completesAt=330).
-    // Cycle 1 completes at tick 330: deposit item, continue (no same-tick restart).
-    // Cycle 2 starts at tick 331 (completesAt=361).
-    // Cycle 2 completes at tick 361: deposit item → buffer=2, cycle 3 stalls.
-    // Need to process through tick 361: 362 ticks total.
+    // Cycle 1 completes at tick 330 and cycle 2 starts in that same tick
+    // (completesAt=360). Cycle 2 completes at tick 360: deposit item -> 2 items held,
+    // which fills the buffer (capacity 2), so cycle 3 cannot start.
+    // Need to process through tick 360: 361 ticks total.
     runTicks(f.bs, f.cfg, f.state, f.belts, f.stock,
              static_cast<int>(secondsToTicks(10.0))
-             + 2 * static_cast<int>(secondsToTicks(1.0)) + 2,
+             + 2 * static_cast<int>(secondsToTicks(1.0)) + 1,
              tick);
 
     const Building* b = findBuilding(f.state, id);
@@ -512,6 +540,49 @@ TEST_CASE("BuildingSystem: miner output buffer stalls when full", "[building]")
     REQUIRE_FALSE(b->production.has_value());
 }
 
+TEST_CASE("BuildingSystem: the next cycle starts on the tick the last one completed",
+          "[building]")
+{
+    // A cycle takes exactly its recipe duration, so a building whose output keeps
+    // draining produces at the configured rate (REQ-MAT-CYCLE). An idle tick between
+    // cycles would cost a one-second recipe about 3% of its throughput.
+    PlacementFixture f;
+
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::Miner, QPoint(0, 0), Rotation::East, 0).value();
+    f.bs.setRecipe(f.state, id, "mine_iron_ore");
+
+    const Tick cycleTicks = secondsToTicks(1.0);  // mine_iron_ore duration
+
+    Tick tick = 0;
+    // Construction completes at tick 300 and cycle 1 starts in that same tick.
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock,
+             static_cast<int>(secondsToTicks(10.0)) + 1, tick);
+    const Building* b = findBuilding(f.state, id);
+    REQUIRE(b != nullptr);
+    REQUIRE(b->production.has_value());
+    const Tick firstCompletesAt = b->production->completesAt;
+
+    // Process up to and including that completion tick: the next cycle is already
+    // running, due exactly one duration later rather than one duration plus a tick.
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock, static_cast<int>(cycleTicks), tick);
+    b = findBuilding(f.state, id);
+    REQUIRE(b->getOutputItemCount() == 1);
+    REQUIRE(b->production.has_value());
+    REQUIRE(b->production->completesAt == firstCompletesAt + cycleTicks);
+
+    // Nothing hauls the ore away here, so the buffer (capacity 2) would stall the third
+    // cycle. Drain it and confirm the cadence holds across the next boundary too.
+    f.bs.forEachBuilding(f.state, [](Building& building) {
+        building.outputBuffer.items.clear();
+        for (std::vector<BeltItemSlot>& lane : building.emergingItems) { lane.clear(); }
+    });
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock, static_cast<int>(cycleTicks), tick);
+    b = findBuilding(f.state, id);
+    REQUIRE(b->production.has_value());
+    REQUIRE(b->production->completesAt == firstCompletesAt + 2 * cycleTicks);
+}
+
 // ---------------------------------------------------------------------------
 // REQ-UI-DEBUG-OVERLAY production counts
 // ---------------------------------------------------------------------------
@@ -585,12 +656,13 @@ TEST_CASE("BuildingSystem: smelter input buffer fills from adjacent west-flowing
     // Smelter mask ["AA ","AA>"] → body (0,0),(1,0),(0,1),(1,1).
     // Output port (2,1) East.  Input port example: (2,0) West.
     const BuildingId sid = f.bs.place(f.state, BuildingType::Smelter, QPoint(0, 0), Rotation::East, 0).value();
-    // Smelters have no recipe selection (REQ-BLD-SMELTER); they auto-accept any
-    // ore/scrap that is an input to a smelter recipe.
+    // A smelter starts with no recipe and picks one from the first material offered to
+    // it (REQ-BLD-AUTO-RECIPE), which is what lets it accept the ore below.
 
     // Complete construction (15s → tick 450+1 = 451 ticks).
     Tick tick = 0;
     runTicks(f.bs, f.cfg, f.state, f.belts, f.stock, static_cast<int>(secondsToTicks(15.0)) + 1, tick);
+    REQUIRE(findBuilding(f.state, sid)->recipeId.empty());
 
     // Place west-flowing belt at (2,0): belt flows West, delivers to smelter.
     f.belts.placeBelt(QPoint(2, 0), Rotation::West);
@@ -601,6 +673,13 @@ TEST_CASE("BuildingSystem: smelter input buffer fills from adjacent west-flowing
 
     const Building* b = findBuilding(f.state, sid);
     REQUIRE(b != nullptr);
+    // The ore selected the recipe that consumes it, and its buffers were sized for that
+    // recipe alone -- copper ore is not one of its inputs any more.
+    REQUIRE(b->recipeId == "iron_ingot");
+    REQUIRE(b->inputBuffer.caps.count(ItemType{"iron_ore"}) == 1);
+    REQUIRE(b->inputBuffer.caps.count(ItemType{"copper_ore"}) == 0);
+    REQUIRE(b->outputBuffer.caps.count(ItemType{"iron_ingot"}) == 1);
+    REQUIRE(b->outputBuffer.caps.count(ItemType{"copper_ingot"}) == 0);
     // The item was accepted; it may still be travelling inward on the input belt,
     // so count buffered + in-transit (REQ-MAT-INPUT-INTAKE).
     REQUIRE(b->pendingInputCount(ItemType{"iron_ore"}) >= 1);
@@ -705,10 +784,10 @@ TEST_CASE("BuildingSystem: smelter auto-smelts ore without a recipe selection",
     REQUIRE(hasIronIngot);
 }
 
-// With mixed inputs, the smelter runs whichever recipe is currently satisfiable
-// and leaves an incomplete batch of another input waiting (see the union-of-
-// inputs caps in initAutoBuffers).
-TEST_CASE("BuildingSystem: smelter runs a satisfiable recipe while an incomplete batch waits",
+// A belt carrying mixed ore is the realistic case for REQ-BLD-AUTO-RECIPE: the first ore
+// to arrive settles the recipe, and everything else on that belt is refused rather than
+// smelted alongside it.
+TEST_CASE("BuildingSystem: mixed ore on one belt leaves the smelter on the first ore's recipe",
           "[building]")
 {
     PlacementFixture f(kFastBeltSpeed_tps);
@@ -718,8 +797,7 @@ TEST_CASE("BuildingSystem: smelter runs a satisfiable recipe while an incomplete
     Tick tick = 0;
     runTicks(f.bs, f.cfg, f.state, f.belts, f.stock, static_cast<int>(secondsToTicks(15.0)) + 1, tick);
 
-    // Feed 1 iron_ore (iron_ingot needs 2 — incomplete) then 2 copper_ore
-    // (copper_ingot needs 2 — satisfiable) via the west-flowing input belt.
+    // Feed 1 iron_ore, then 2 copper_ore, via the west-flowing input belt.
     f.belts.placeBelt(QPoint(2, 0), Rotation::West);
     const char* fed[] = { "iron_ore", "copper_ore", "copper_ore" };
     for (const char* id : fed)
@@ -729,24 +807,26 @@ TEST_CASE("BuildingSystem: smelter runs a satisfiable recipe while an incomplete
         f.bs.tickBeltPull(f.state);
     }
 
-    // copper_ingot cycle is 2.5s; run to completion.
     runTicks(f.bs, f.cfg, f.state, f.belts, f.stock, static_cast<int>(secondsToTicks(2.5)) + 2, tick);
 
     const Building* b = findBuilding(f.state, sid);
     REQUIRE(b != nullptr);
 
-    // Copper was smelted; the lone iron_ore still waits for a second unit.
-    bool hasCopperIngot = false;
+    // The iron ore came first, so the smelter smelts iron and nothing else. The copper
+    // was never taken in, so no copper ingot was made.
+    REQUIRE(b->recipeId == "iron_ingot");
     for (const Item& item : outputSideItems(*b))
     {
-        if (item.type.id == "copper_ingot") { hasCopperIngot = true; }
+        REQUIRE(item.type.id != "copper_ingot");
     }
-    REQUIRE(hasCopperIngot);
+    REQUIRE(b->pendingInputCount(ItemType{"copper_ore"}) == 0);
 
+    // The lone iron ore still waits for a second unit: the recipe needs two.
     const std::map<ItemType, int>::const_iterator ironIt =
         b->inputBuffer.counts.find(ItemType{"iron_ore"});
     REQUIRE(ironIt != b->inputBuffer.counts.end());
     REQUIRE(ironIt->second == 1);
+    REQUIRE_FALSE(b->production.has_value());
 }
 
 // ---------------------------------------------------------------------------
@@ -833,7 +913,8 @@ TEST_CASE("BuildingSystem: direct coupling to a non-consumer leaves the item stu
     REQUIRE(sink != nullptr);
     // Nothing was delivered, and the producer's output side has backed up to its cap.
     REQUIRE(sink->pendingInputCount(ItemType{"iron_ore"}) == 0);
-    REQUIRE(miner->getOutputItemCount() == miner->outputBuffer.capacity);
+    REQUIRE(miner->getOutputItemCount(ItemType{"iron_ore"})
+            == miner->outputBuffer.caps.at(ItemType{"iron_ore"}));
 }
 
 // ---------------------------------------------------------------------------
@@ -870,28 +951,379 @@ TEST_CASE("BuildingSystem: setRecipe clears output buffer and active production"
 }
 
 // ---------------------------------------------------------------------------
-// Reprocessing plant — output buffer capacity (REQ-MAT-OUTPUT-BUFFER-REPROCESSING)
+// Reprocessing plant -- per-item output buffers (REQ-MAT-OUTPUT-BUFFER)
 // ---------------------------------------------------------------------------
 
-TEST_CASE("BuildingSystem: reprocessing plant output buffer capacity equals max output per roll",
+TEST_CASE("ConfigLoader: the outputs shorthand and one output_group load alike",
+          "[config]")
+{
+    // `outputs = [...]` is exactly one group holding those items (REQ-MAT-OUTPUT-GROUP),
+    // so a recipe written either way behaves identically.
+    PlacementFixture f;
+
+    const RecipeDef* shorthand =
+        f.cfg.recipes.findRecipeDef("iron_ingot", BuildingType::Smelter);
+    REQUIRE(shorthand != nullptr);
+    REQUIRE(shorthand->outputGroups.size() == 1);
+    REQUIRE_FALSE(shorthand->outputGroups.front().probability.has_value());
+
+    // Sizing and the cycle gate read it as one group like any other.
+    Building smelter; smelter.type = BuildingType::Smelter;
+    smelter.recipeId = shorthand->id;
+    initBuffers(smelter, *shorthand);
+    REQUIRE(smelter.outputBuffer.caps.at(ItemType{"iron_ingot"})
+            == 2 * shorthand->outputGroups.front().items.front().amount);
+    REQUIRE(recipeOutputsFit(smelter, *shorthand));
+}
+
+TEST_CASE("BuildingSystem: a single-group recipe consumes no randomness", "[building]")
+{
+    // Nothing is picked where there is one group, so no draw is made (REQ-MAT-OUTPUT-GROUP).
+    // Drawing here would consume entropy for every ordinary recipe and shift every later
+    // random outcome, which is what the two fixtures below would expose: they differ only
+    // in how far their generators have been advanced.
+    PlacementFixture quiet;
+    PlacementFixture advanced;
+    for (int i = 0; i < 50; ++i) { (void)advanced.rng(); }
+
+    Tick tickA = 0;
+    Tick tickB = 0;
+    const BuildingId a =
+        quiet.bs.place(quiet.state, BuildingType::Miner, QPoint(0, 0), Rotation::East, 0).value();
+    const BuildingId b =
+        advanced.bs.place(advanced.state, BuildingType::Miner, QPoint(0, 0), Rotation::East, 0).value();
+    quiet.bs.setRecipe(quiet.state, a, "mine_iron_ore");
+    advanced.bs.setRecipe(advanced.state, b, "mine_iron_ore");
+
+    const int ticks = static_cast<int>(secondsToTicks(10.0)) + 40;
+    runTicks(quiet.bs, quiet.cfg, quiet.state, quiet.belts, quiet.stock, ticks, tickA);
+    runTicks(advanced.bs, advanced.cfg, advanced.state, advanced.belts, advanced.stock,
+             ticks, tickB);
+
+    const Building* minerA = findBuilding(quiet.state, a);
+    const Building* minerB = findBuilding(advanced.state, b);
+    REQUIRE(minerA != nullptr);
+    REQUIRE(minerB != nullptr);
+    REQUIRE(minerA->getOutputItemCount() > 0);
+    REQUIRE(minerA->getOutputItemCount() == minerB->getOutputItemCount());
+    REQUIRE(minerA->production.has_value() == minerB->production.has_value());
+}
+
+TEST_CASE("BuildingSystem: a group's items are sized and gated together", "[building]")
+{
+    // A group yields all of its items at once (REQ-MAT-OUTPUT-GROUP), so each is buffered
+    // at twice its own amount and the cycle needs room for all of them at once. No config
+    // recipe has a multi-item group yet, so one is built here.
+    PlacementFixture f;
+
+    RecipeDef recipe;
+    recipe.id              = "multi_item_group";
+    recipe.building        = BuildingType::Assembler;
+    recipe.durationSeconds = 1.0;
+    recipe.inputs.push_back(RecipeIngredient{"iron_ore", 1});
+    RecipeOutputGroup group;
+    group.items.push_back(RecipeOutput{"iron_ingot", 2});
+    group.items.push_back(RecipeOutput{"silicon", 1});
+    recipe.outputGroups.push_back(group);
+
+    Building assembler; assembler.type = BuildingType::Assembler;
+    initBuffers(assembler, recipe);
+    REQUIRE(assembler.outputBuffer.caps.at(ItemType{"iron_ingot"}) == 4);
+    REQUIRE(assembler.outputBuffer.caps.at(ItemType{"silicon"})    == 2);
+
+    // Both fit while both have room.
+    REQUIRE(recipeOutputsFit(assembler, recipe));
+
+    // One item of the group short of room blocks the whole cycle, even though the other
+    // still has plenty: the group cannot be produced in halves.
+    assembler.outputBuffer.items.push_back(makeItem("silicon"));
+    assembler.outputBuffer.items.push_back(makeItem("silicon"));
+    REQUIRE(outputBufferHasRoom(assembler, ItemType{"iron_ingot"}, 2));
+    REQUIRE_FALSE(outputBufferHasRoom(assembler, ItemType{"silicon"}, 1));
+    REQUIRE_FALSE(recipeOutputsFit(assembler, recipe));
+}
+
+TEST_CASE("BuildingSystem: a group with a locked item is never picked", "[building]")
+{
+    // A group's items come together, so a group holding any locked item is dropped whole
+    // (REQ-LOCK-OUTPUT-POOL). Here only circuit_board is unlocked, so every cycle must
+    // yield that group however the weights are stacked -- iron_ingot's group carries the
+    // largest weight of the three and would dominate were the filter not applied.
+    PlacementFixture f(std::nullopt,
+                       [](const std::string& id) { return id == "circuit_board"; });
+
+    Tick tick = 0;
+    const BuildingId id = f.bs.place(f.state, BuildingType::ReprocessingPlant,
+                                     QPoint(0, 0), Rotation::East, 0).value();
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock,
+             static_cast<int>(secondsToTicks(25.0)) + 1, tick);
+    f.bs.setRecipe(f.state, id, "reprocessing_cycle");
+
+    // Run many cycles, refilling the scrap and draining the output each time so the plant
+    // never stalls. A broken filter would show iron_ingot within a few rounds.
+    int produced = 0;
+    for (int round = 0; round < 20; ++round)
+    {
+        f.bs.forEachBuilding(f.state, [](Building& building) {
+            if (building.type != BuildingType::ReprocessingPlant) { return; }
+            building.inputBuffer.counts[ItemType{"scrap"}] =
+                building.inputBuffer.caps.at(ItemType{"scrap"});
+            building.outputBuffer.items.clear();
+            for (std::vector<BeltItemSlot>& lane : building.emergingItems) { lane.clear(); }
+        });
+        runTicks(f.bs, f.cfg, f.state, f.belts, f.stock,
+                 static_cast<int>(secondsToTicks(3.0)) + 1, tick);
+
+        for (const Item& item : outputSideItems(*findBuilding(f.state, id)))
+        {
+            CHECK(item.type.id == "circuit_board");
+            ++produced;
+        }
+    }
+    REQUIRE(produced > 0);
+}
+
+TEST_CASE("BuildingSystem: reprocessing plant sizes one output buffer per possible roll",
           "[building]")
 {
     PlacementFixture f;
 
     const BuildingId id = f.bs.place(f.state, BuildingType::ReprocessingPlant,
                                   QPoint(0, 0), Rotation::East, 0).value();
-    // Reprocessing plants have no recipe selection (REQ-BLD-REPROCESSING); the
-    // single reprocessing recipe is applied automatically on completion.
 
     // Complete construction (25s).
     Tick tick = 0;
     runTicks(f.bs, f.cfg, f.state, f.belts, f.stock, static_cast<int>(secondsToTicks(25.0)) + 1, tick);
 
+    // A plant holds no buffers until it has a recipe (REQ-BLD-AUTO-RECIPE); selecting
+    // one sizes them, exactly as the first scrap offered to it would.
+    REQUIRE(findBuilding(f.state, id)->outputBuffer.caps.empty());
+    f.bs.setRecipe(f.state, id, "reprocessing_cycle");
+
     const Building* b = findBuilding(f.state, id);
     REQUIRE(b != nullptr);
     // reprocessing_cycle outputs: 2 iron_ingot (60%), 1 circuit_board (30%),
-    // 1 advanced_alloy (10%).  Max per roll = 2.  Capacity = 2 (1× max).
-    REQUIRE(b->outputBuffer.capacity == 2);
+    // 1 advanced_alloy (10%). One roll yields one of them, so each buffer holds twice
+    // that outcome's own amount (REQ-MAT-OUTPUT-BUFFER).
+    REQUIRE(b->outputBuffer.caps.size() == 3);
+    REQUIRE(b->outputBuffer.caps.at(ItemType{"iron_ingot"})    == 4);
+    REQUIRE(b->outputBuffer.caps.at(ItemType{"circuit_board"}) == 2);
+    REQUIRE(b->outputBuffer.caps.at(ItemType{"advanced_alloy"}) == 2);
+}
+
+TEST_CASE("BuildingSystem: one full output buffer stops the plant even when the others have room",
+          "[building]")
+{
+    // The gate that replaced the old one-item cap: a cycle may only start when *every*
+    // outcome would fit, because the roll is committed once it starts (REQ-MAT-CYCLE).
+    // Were the plant to roll first and skip a result that does not fit, a player could
+    // stall one output belt to filter the distribution towards the other items.
+    PlacementFixture f(kFastBeltSpeed_tps);
+
+    const BuildingId id = f.bs.place(f.state, BuildingType::ReprocessingPlant,
+                                     QPoint(0, 0), Rotation::East, 0).value();
+    Tick tick = 0;
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock,
+             static_cast<int>(secondsToTicks(25.0)) + 1, tick);
+
+    // Feed a full cycle's scrap (5) so only the output side can hold it back.
+    f.belts.placeBelt(QPoint(-1, 0), Rotation::East);
+    for (int i = 0; i < 5; ++i)
+    {
+        f.belts.tryPutItem(QPoint(-1, 0), makeItem("scrap"), Rotation::East);
+        f.belts.tick();
+        f.bs.tickBeltPull(f.state);
+    }
+
+    // Fill the iron_ingot buffer to its cap and leave the other two empty.
+    f.bs.forEachBuilding(f.state, [](Building& building) {
+        if (building.type != BuildingType::ReprocessingPlant) { return; }
+        const int cap = building.outputBuffer.caps.at(ItemType{"iron_ingot"});
+        for (int i = 0; i < cap; ++i)
+        {
+            building.outputBuffer.items.push_back(makeItem("iron_ingot"));
+        }
+    });
+
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock, 5, tick);
+
+    const Building* b = findBuilding(f.state, id);
+    REQUIRE(b != nullptr);
+    // circuit_board and advanced_alloy have room, but iron_ingot does not, so no cycle
+    // starts at all and the scrap is still waiting.
+    REQUIRE(b->outputBuffer.caps.at(ItemType{"circuit_board"}) > 0);
+    REQUIRE(outputBufferHasRoom(*b, ItemType{"circuit_board"}, 1));
+    REQUIRE_FALSE(outputBufferHasRoom(*b, ItemType{"iron_ingot"}, 1));
+    REQUIRE_FALSE(b->production.has_value());
+    REQUIRE(b->pendingInputCount(ItemType{"scrap"}) == 5);
+    REQUIRE(getProductionStatus(f.cfg, *b) == ProductionStatus::Blocked);
+}
+
+TEST_CASE("BuildingSystem: reprocessing plant runs a second cycle while holding the first output",
+          "[building]")
+{
+    // Its buffers hold twice each outcome's amount (REQ-MAT-OUTPUT-BUFFER), so a held
+    // result no longer stops the next cycle. The old one-item cap made this impossible:
+    // whatever the first roll was, the plant stalled until that item left the building.
+    PlacementFixture f(kFastBeltSpeed_tps);
+
+    const BuildingId id = f.bs.place(f.state, BuildingType::ReprocessingPlant,
+                                     QPoint(0, 0), Rotation::East, 0).value();
+    Tick tick = 0;
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock,
+             static_cast<int>(secondsToTicks(25.0)) + 1, tick);
+
+    // Two cycles' worth of scrap (5 each), which is exactly the input cap.
+    f.belts.placeBelt(QPoint(-1, 0), Rotation::East);
+    for (int i = 0; i < 10; ++i)
+    {
+        f.belts.tryPutItem(QPoint(-1, 0), makeItem("scrap"), Rotation::East);
+        f.belts.tick();
+        f.bs.tickBeltPull(f.state);
+    }
+    REQUIRE(findBuilding(f.state, id)->pendingInputCount(ItemType{"scrap"}) == 10);
+
+    // No belt carries the output away, so the first cycle's result is still held.
+    // reprocessing_cycle runs 3s; run through the completion tick.
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock,
+             static_cast<int>(secondsToTicks(3.0)) + 1, tick);
+
+    const Building* b = findBuilding(f.state, id);
+    REQUIRE(b != nullptr);
+    REQUIRE(b->getOutputItemCount() > 0);
+    // Whichever outcome was rolled, every outcome still fits, so the second cycle is
+    // already running rather than the plant sitting blocked.
+    REQUIRE(b->production.has_value());
+    REQUIRE(getProductionStatus(f.cfg, *b) == ProductionStatus::Producing);
+}
+
+// ---------------------------------------------------------------------------
+// Automatic recipe selection (REQ-BLD-AUTO-RECIPE)
+// ---------------------------------------------------------------------------
+
+// Places a smelter and runs it to completion, leaving it with no recipe.
+static BuildingId buildSmelter(PlacementFixture& f, QPoint anchor, Tick& tick)
+{
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::Smelter, anchor, Rotation::East, 0).value();
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock,
+             static_cast<int>(secondsToTicks(15.0)) + 1, tick);
+    return id;
+}
+
+TEST_CASE("BuildingSystem: an unset auto-recipe building is unconfigured", "[building]")
+{
+    // It holds no recipe until one is offered to it, so it reads grey like any other
+    // unconfigured building (REQ-BLD-AUTO-RECIPE, REQ-UI-STATUS-LIGHT).
+    PlacementFixture f;
+    Tick tick = 0;
+    const BuildingId id = buildSmelter(f, QPoint(0, 0), tick);
+
+    const Building* b = findBuilding(f.state, id);
+    REQUIRE(b != nullptr);
+    REQUIRE(b->recipeId.empty());
+    REQUIRE(b->inputBuffer.caps.empty());
+    REQUIRE(b->outputBuffer.caps.empty());
+    REQUIRE(getProductionStatus(f.cfg, *b) == ProductionStatus::Unconfigured);
+}
+
+TEST_CASE("BuildingSystem: a set recipe is never replaced by a later material",
+          "[building]")
+{
+    // Once set the recipe is the player's to change: a material belonging to another of
+    // its recipes is simply not an accepted input (REQ-BLD-AUTO-RECIPE).
+    PlacementFixture f(kFastBeltSpeed_tps);
+    Tick tick = 0;
+    const BuildingId id = buildSmelter(f, QPoint(0, 0), tick);
+
+    // Iron ore first, which selects the iron recipe.
+    f.belts.placeBelt(QPoint(2, 0), Rotation::West);
+    f.belts.tryPutItem(QPoint(2, 0), makeItem("iron_ore"));
+    f.belts.tick();
+    f.bs.tickBeltPull(f.state);
+    REQUIRE(findBuilding(f.state, id)->recipeId == "iron_ingot");
+
+    // Copper ore next: refused, and the recipe stands.
+    f.belts.tryPutItem(QPoint(2, 0), makeItem("copper_ore"));
+    f.belts.tick();
+    f.bs.tickBeltPull(f.state);
+
+    const Building* b = findBuilding(f.state, id);
+    REQUIRE(b->recipeId == "iron_ingot");
+    REQUIRE(b->pendingInputCount(ItemType{"copper_ore"}) == 0);
+    // The copper is still sitting on the belt, refused rather than swallowed.
+    REQUIRE(f.belts.peekItem(westPort(QPoint(2, 0))).has_value());
+}
+
+TEST_CASE("BuildingSystem: a manually selected recipe is not overridden", "[building]")
+{
+    // The player's selection is a recipe like any other, so auto-selection stays out of
+    // the way and the smelter refuses ore it does not smelt (REQ-BLD-AUTO-RECIPE).
+    PlacementFixture f(kFastBeltSpeed_tps);
+    Tick tick = 0;
+    const BuildingId id = buildSmelter(f, QPoint(0, 0), tick);
+
+    f.bs.setRecipe(f.state, id, "copper_ingot");
+    REQUIRE(findBuilding(f.state, id)->recipeId == "copper_ingot");
+
+    f.belts.placeBelt(QPoint(2, 0), Rotation::West);
+    f.belts.tryPutItem(QPoint(2, 0), makeItem("iron_ore"));
+    f.belts.tick();
+    f.bs.tickBeltPull(f.state);
+
+    const Building* b = findBuilding(f.state, id);
+    REQUIRE(b->recipeId == "copper_ingot");
+    REQUIRE(b->pendingInputCount(ItemType{"iron_ore"}) == 0);
+}
+
+TEST_CASE("BuildingSystem: selecting a different recipe frees a stuck auto-recipe building",
+          "[building]")
+{
+    // A smelter left holding part of a cycle nothing feeds any more is freed by
+    // selecting another recipe, which clears the buffers -- that is why no separate
+    // clear action exists (REQ-BLD-AUTO-RECIPE, REQ-MAT-INPUT-BUFFER).
+    PlacementFixture f(kFastBeltSpeed_tps);
+    Tick tick = 0;
+    const BuildingId id = buildSmelter(f, QPoint(0, 0), tick);
+
+    // One iron ore, where the recipe needs two: it can never run.
+    f.belts.placeBelt(QPoint(2, 0), Rotation::West);
+    f.belts.tryPutItem(QPoint(2, 0), makeItem("iron_ore"));
+    f.belts.tick();
+    f.bs.tickBeltPull(f.state);
+    runTicks(f.bs, f.cfg, f.state, f.belts, f.stock, 30, tick);
+
+    const Building* stuck = findBuilding(f.state, id);
+    REQUIRE(stuck->recipeId == "iron_ingot");
+    REQUIRE(stuck->pendingInputCount(ItemType{"iron_ore"}) == 1);
+    REQUIRE_FALSE(stuck->production.has_value());
+
+    f.bs.setRecipe(f.state, id, "copper_ingot");
+    const Building* freed = findBuilding(f.state, id);
+    REQUIRE(freed->recipeId == "copper_ingot");
+    REQUIRE(freed->pendingInputCount(ItemType{"iron_ore"}) == 0);
+    REQUIRE(freed->inputBuffer.caps.count(ItemType{"copper_ore"}) == 1);
+}
+
+TEST_CASE("BuildingSystem: selecting (Auto) returns the building to automatic selection",
+          "[building]")
+{
+    // The dialog's clearing option unsets the recipe rather than leaving the building
+    // idle for good: the next material offered selects one again (REQ-BLD-AUTO-RECIPE).
+    PlacementFixture f(kFastBeltSpeed_tps);
+    Tick tick = 0;
+    const BuildingId id = buildSmelter(f, QPoint(0, 0), tick);
+
+    f.bs.setRecipe(f.state, id, "copper_ingot");
+    f.bs.setRecipe(f.state, id, std::string());  // the "(Auto)" option
+    REQUIRE(findBuilding(f.state, id)->recipeId.empty());
+
+    f.belts.placeBelt(QPoint(2, 0), Rotation::West);
+    f.belts.tryPutItem(QPoint(2, 0), makeItem("iron_ore"));
+    f.belts.tick();
+    f.bs.tickBeltPull(f.state);
+
+    REQUIRE(findBuilding(f.state, id)->recipeId == "iron_ingot");
 }
 
 TEST_CASE("BuildingSystem: reprocessing plant produces one cycle output then stalls",
@@ -902,8 +1334,8 @@ TEST_CASE("BuildingSystem: reprocessing plant produces one cycle output then sta
 
     const BuildingId id = f.bs.place(f.state, BuildingType::ReprocessingPlant,
                                   QPoint(0, 0), Rotation::East, 0).value();
-    // Reprocessing plants have no recipe selection (REQ-BLD-REPROCESSING); the
-    // single reprocessing recipe is applied automatically on completion.
+    // The plant selects its recipe from the first scrap offered to it
+    // (REQ-BLD-AUTO-RECIPE), which is what the belt feeding below does.
 
     // Complete construction (25s).
     Tick tick = 0;
@@ -1081,10 +1513,12 @@ TEST_CASE("isConfigurableBuildingType: only types with player-facing settings",
     CHECK(isConfigurableBuildingType(BuildingType::Shipyard));
     CHECK(isConfigurableBuildingType(BuildingType::Splitter));
 
-    // Smelter and Reprocessing Plant run implicit recipes (REQ-BLD-SMELTER,
-    // REQ-BLD-REPROCESSING) and the rest have no settings whatsoever.
-    CHECK_FALSE(isConfigurableBuildingType(BuildingType::Smelter));
-    CHECK_FALSE(isConfigurableBuildingType(BuildingType::ReprocessingPlant));
+    // Smelter and Reprocessing Plant carry a recipe like any other, even though they can
+    // also select it themselves (REQ-BLD-AUTO-RECIPE).
+    CHECK(isConfigurableBuildingType(BuildingType::Smelter));
+    CHECK(isConfigurableBuildingType(BuildingType::ReprocessingPlant));
+
+    // The rest have no settings whatsoever.
     CHECK_FALSE(isConfigurableBuildingType(BuildingType::SalvageBay));
     CHECK_FALSE(isConfigurableBuildingType(BuildingType::Belt));
     CHECK_FALSE(isConfigurableBuildingType(BuildingType::TunnelEntry));
@@ -1134,8 +1568,15 @@ TEST_CASE("resolveBlueprintGhost: a partial overlap of the same type is invalid"
     // Both footprints stay on the asteroid, so terrain is not what fails here.
     f.bs.place(f.state, BuildingType::Smelter, QPoint(-3, 0), Rotation::East, 0);
 
-    CHECK(resolveOne(f, BuildingType::Smelter, QPoint(-2, 0), Rotation::East).action
+    // Judged on where it sits, with no cursor to hit-test: the overlap is what decides.
+    CHECK(resolveInConstellation(f, BuildingType::Smelter, QPoint(-2, 0), Rotation::East).action
           == BlueprintGhostAction::Invalid);
+
+    // With the cursor on the existing smelter the single-building gesture answers first
+    // and hands it the settings, since a smelter carries a recipe (REQ-BLD-AUTO-RECIPE,
+    // REQ-UI-BLUEPRINT-TRANSFER) -- the same as for a miner.
+    CHECK(resolveOne(f, BuildingType::Smelter, QPoint(-2, 0), Rotation::East).action
+          == BlueprintGhostAction::Transfer);
 }
 
 TEST_CASE("resolveBlueprintGhost: a single configurable building transfers its settings",
@@ -1296,11 +1737,11 @@ TEST_CASE("resolveBlueprintGhost: a constellation mixes transfers and plain over
     REQUIRE(miner.action == BlueprintGhostAction::Transfer);
     CHECK(*miner.targetId == minerId);
 
-    // A smelter runs an implicit recipe (REQ-BLD-SMELTER), so there is nothing to hand
-    // over and it is simply left as it is.
+    // A smelter carries a recipe too now (REQ-BLD-AUTO-RECIPE), so a blueprint of one
+    // has something to hand over just as the miner does.
     const BlueprintGhostResolved smelter =
         resolveInConstellation(f, BuildingType::Smelter, QPoint(-5, 0), Rotation::East);
-    REQUIRE(smelter.action == BlueprintGhostAction::CompatibleOverlap);
+    REQUIRE(smelter.action == BlueprintGhostAction::Transfer);
     CHECK(*smelter.targetId == smelterId);
 }
 
@@ -1515,41 +1956,194 @@ TEST_CASE("BuildingSystem: getProductionStatus classifies production state", "[b
         miner.production = Production{};
         REQUIRE(statusOf(miner) == ProductionStatus::Producing);     // active cycle -> green
 
-        // A miner has no inputs, so its only idle reason is a full output buffer.
+        // A miner has no inputs, so its only idle reason is an output buffer with no
+        // room for the next cycle's output.
         miner.production = std::nullopt;
-        miner.outputBuffer.capacity = 2;
-        miner.outputBuffer.items    = { makeItem("iron_ore"), makeItem("iron_ore") };
+        miner.outputBuffer.caps[ItemType{"iron_ore"}] = 2;
+        miner.outputBuffer.items = { makeItem("iron_ore"), makeItem("iron_ore") };
         REQUIRE(statusOf(miner) == ProductionStatus::Blocked);       // -> yellow
+
+        // One item handed off: the next cycle fits again, so the idle tick between two
+        // cycles reads as producing rather than blinking yellow (REQ-UI-STATUS-LIGHT).
+        miner.outputBuffer.items.pop_back();
+        REQUIRE(statusOf(miner) == ProductionStatus::Producing);     // -> green
+
+        // An emerging item has not left the building, so it fills the freed room and
+        // blocks the cycle again (REQ-MAT-OUTPUT-EMERGE).
+        miner.emergingItems.push_back({ BeltItemSlot{ makeItem("iron_ore"), 0.5 } });
+        REQUIRE(miner.getOutputItemCount(ItemType{"iron_ore"}) == 2);
+        REQUIRE(statusOf(miner) == ProductionStatus::Blocked);       // -> yellow
+
+        // Another item's backlog is measured against its own buffer, so it changes
+        // nothing here (REQ-MAT-OUTPUT-BUFFER).
+        miner.outputBuffer.caps[ItemType{"copper_ore"}] = 2;
+        miner.outputBuffer.items.push_back(makeItem("copper_ore"));
+        REQUIRE(statusOf(miner) == ProductionStatus::Blocked);
+        miner.outputBuffer.items.clear();
+        REQUIRE(statusOf(miner) == ProductionStatus::Producing);
     }
 
-    SECTION("Assembler: starved vs blocked, input-missing takes precedence")
+    SECTION("Assembler: starved, the transient between cycles, then blocked")
     {
         Building assembler; assembler.type = BuildingType::Assembler;
         assembler.recipeId = assemblerRecipe->id;
+        // Sized the way the simulation sizes it (REQ-MAT-OUTPUT-BUFFER).
+        initBuffers(assembler, *assemblerRecipe);
+
+        const std::string outputItemId =
+            assemblerRecipe->outputGroups.front().items.front().item;
+        int cycleOutput = 0;
+        for (const RecipeOutput& out : assemblerRecipe->outputGroups.front().items)
+        {
+            cycleOutput += out.amount;
+        }
+        REQUIRE(cycleOutput > 0);
 
         // Idle with inputs missing -> red.
         REQUIRE(statusOf(assembler) == ProductionStatus::Starved);
 
-        // Inputs present but idle -> the only remaining reason is a full output
-        // buffer -> yellow.
+        // Inputs present and the output fits: nothing blocks a cycle, so the building
+        // is merely between cycles -> green, not yellow (REQ-UI-STATUS-LIGHT).
         for (const RecipeIngredient& ing : assemblerRecipe->inputs)
         {
             assembler.inputBuffer.counts[ItemType{ing.item}] = ing.amount;
         }
+        REQUIRE(statusOf(assembler) == ProductionStatus::Producing);
+
+        // That item's own buffer filled to within less than one cycle's output of its
+        // capacity: no cycle can start -> yellow.
+        for (int i = 0; i < cycleOutput + 1; ++i)
+        {
+            assembler.outputBuffer.items.push_back(makeItem(outputItemId));
+        }
         REQUIRE(statusOf(assembler) == ProductionStatus::Blocked);
 
-        // Inputs missing AND output full -> red wins over yellow.
+        // Inputs missing AND output blocked -> red wins over yellow.
         assembler.inputBuffer.counts.clear();
-        assembler.outputBuffer.capacity = 2;
-        assembler.outputBuffer.items    = { makeItem("x"), makeItem("x") };
         REQUIRE(statusOf(assembler) == ProductionStatus::Starved);
     }
 
-    SECTION("Smelter (auto-recipe) is never grey")
+    SECTION("A multi-item cycle blocks before the output buffer is full")
     {
+        // Free space smaller than one cycle's output stops the cycle even though the
+        // buffer still has room, so yellow is not the same as "full" (REQ-MAT-CYCLE).
+        const RecipeDef* multiOutputRecipe = nullptr;
+        for (const RecipeDef& r : f.cfg.recipes.recipes)
+        {
+            if (r.building != BuildingType::Assembler || r.inputs.empty()) { continue; }
+            int total = 0;
+            for (const RecipeOutput& out : r.outputGroups.front().items)
+            {
+                total += out.amount;
+            }
+            if (total >= 2) { multiOutputRecipe = &r; break; }
+        }
+        REQUIRE(multiOutputRecipe != nullptr);
+
+        int cycleOutput = 0;
+        for (const RecipeOutput& out : multiOutputRecipe->outputGroups.front().items)
+        {
+            cycleOutput += out.amount;
+        }
+        const std::string outputItemId =
+            multiOutputRecipe->outputGroups.front().items.front().item;
+
+        Building assembler; assembler.type = BuildingType::Assembler;
+        assembler.recipeId = multiOutputRecipe->id;
+        initBuffers(assembler, *multiOutputRecipe);
+        for (const RecipeIngredient& ing : multiOutputRecipe->inputs)
+        {
+            assembler.inputBuffer.counts[ItemType{ing.item}] = ing.amount;
+        }
+
+        // One item short of a full cycle's worth of free space.
+        for (int i = 0; i < cycleOutput + 1; ++i)
+        {
+            assembler.outputBuffer.items.push_back(makeItem(outputItemId));
+        }
+        REQUIRE(assembler.getOutputItemCount(ItemType{outputItemId})
+                < assembler.outputBuffer.caps.at(ItemType{outputItemId}));
+        REQUIRE(statusOf(assembler) == ProductionStatus::Blocked);
+
+        // Exactly one cycle's worth of free space: the cycle fits again.
+        assembler.outputBuffer.items.pop_back();
+        REQUIRE(statusOf(assembler) == ProductionStatus::Producing);
+    }
+
+    SECTION("Reprocessing Plant: blocked once any possible roll has no room")
+    {
+        // The plant rolls one of its outputs per cycle (REQ-BLD-REPROCESSING) and the
+        // roll is committed at cycle start, so every outcome has to fit before it may
+        // begin: one full buffer blocks it whatever room the others have (REQ-MAT-CYCLE).
+        const RecipeDef* reprocessingRecipe = nullptr;
+        for (const RecipeDef& r : f.cfg.recipes.recipes)
+        {
+            if (r.building == BuildingType::ReprocessingPlant && !r.inputs.empty())
+            {
+                reprocessingRecipe = &r;
+                break;
+            }
+        }
+        REQUIRE(reprocessingRecipe != nullptr);
+        REQUIRE(reprocessingRecipe->outputGroups.size() >= 2);
+
+        Building plant; plant.type = BuildingType::ReprocessingPlant;
+        plant.recipeId = reprocessingRecipe->id;
+        initBuffers(plant, *reprocessingRecipe);
+        for (const RecipeIngredient& ing : reprocessingRecipe->inputs)
+        {
+            plant.inputBuffer.counts[ItemType{ing.item}] = ing.amount;
+        }
+
+        // Every buffer empty: whatever the roll turns out to be, it fits -> green.
+        REQUIRE(statusOf(plant) == ProductionStatus::Producing);
+
+        // Fill one outcome's buffer and leave the rest untouched -> yellow, even though
+        // the other outcomes still have room.
+        const std::string firstItemId =
+            reprocessingRecipe->outputGroups.front().items.front().item;
+        const std::string lastItemId =
+            reprocessingRecipe->outputGroups.back().items.front().item;
+        for (int i = 0; i < plant.outputBuffer.caps.at(ItemType{firstItemId}); ++i)
+        {
+            plant.outputBuffer.items.push_back(makeItem(firstItemId));
+        }
+        REQUIRE(outputBufferHasRoom(plant, ItemType{lastItemId}, 1));
+        REQUIRE_FALSE(outputBufferHasRoom(plant, ItemType{firstItemId}, 1));
+        REQUIRE(statusOf(plant) == ProductionStatus::Blocked);
+
+        // Without the scrap it is starved regardless of the buffers.
+        plant.inputBuffer.counts.clear();
+        REQUIRE(statusOf(plant) == ProductionStatus::Starved);
+    }
+
+    SECTION("Smelter: grey until it has a recipe, then judged like any other building")
+    {
+        // It holds no recipe until one is offered to it, so grey now applies to it too
+        // (REQ-BLD-AUTO-RECIPE, REQ-UI-STATUS-LIGHT).
         Building smelter; smelter.type = BuildingType::Smelter;
-        // No player-selectable recipe and empty inputs -> red, not grey.
-        REQUIRE(statusOf(smelter) == ProductionStatus::Starved);
+        REQUIRE(statusOf(smelter) == ProductionStatus::Unconfigured);
+
+        const RecipeDef* smelterRecipe = nullptr;
+        for (const RecipeDef& r : f.cfg.recipes.recipes)
+        {
+            if (r.building == BuildingType::Smelter && !r.inputs.empty())
+            {
+                smelterRecipe = &r;
+                break;
+            }
+        }
+        REQUIRE(smelterRecipe != nullptr);
+
+        smelter.recipeId = smelterRecipe->id;
+        initBuffers(smelter, *smelterRecipe);
+        REQUIRE(statusOf(smelter) == ProductionStatus::Starved);  // recipe, but no ore
+
+        for (const RecipeIngredient& ing : smelterRecipe->inputs)
+        {
+            smelter.inputBuffer.counts[ItemType{ing.item}] = ing.amount;
+        }
+        REQUIRE(statusOf(smelter) == ProductionStatus::Producing);
     }
 
     SECTION("Shipyard: unconfigured, then starved without materials, then producing")
@@ -1567,7 +2161,7 @@ TEST_CASE("BuildingSystem: getProductionStatus classifies production state", "[b
     SECTION("Salvage Bay: red when empty, green when holding scrap")
     {
         Building bay; bay.type = BuildingType::SalvageBay;
-        bay.outputBuffer.capacity = 20;
+        bay.outputBuffer.caps[ItemType{"scrap"}] = 20;
         REQUIRE(statusOf(bay) == ProductionStatus::Starved);         // empty -> red
 
         bay.outputBuffer.items = { makeItem("scrap") };

src/test/CMakeLists.txt

@@ -14,8 +14,10 @@ add_files(
     TunnelCompletionTest.cpp
     WorldCoordinatesTest.cpp
     WorldCameraTest.cpp
+    FloatingPanelPlacementTest.cpp
     SelectionControllerTest.cpp
     BuildModeControllerTest.cpp
+    ControlActionTest.cpp
     BuildingTest.cpp
     BuildingConfigTest.cpp
     ShipTest.cpp

src/test/ConfigLoaderTest.cpp

@@ -130,22 +130,26 @@ TEST_CASE("ConfigLoader loads the committed bin/config/ configs end-to-end", "[c
     REQUIRE(*salvageBayIt->tooltip == "Drop-off point for salvage ships.");
     REQUIRE_FALSE(minerIt->tooltip.has_value());
 
-    // recipes.toml — reprocessing cycle has three weighted outputs.
+    // recipes.toml -- the reprocessing cycle is written as three weighted output groups,
+    // each yielding one item (REQ-MAT-OUTPUT-GROUP).
     const auto reproIt = std::find_if(
         cfg.recipes.recipes.begin(), cfg.recipes.recipes.end(),
         [](const RecipeDef& r) { return r.id == "reprocessing_cycle"; });
     REQUIRE(reproIt != cfg.recipes.recipes.end());
     REQUIRE(reproIt->building == BuildingType::ReprocessingPlant);
-    REQUIRE(reproIt->outputs.size() == 3);
-    REQUIRE(reproIt->outputs[0].probability.has_value());
+    REQUIRE(reproIt->outputGroups.size() == 3);
+    REQUIRE(reproIt->outputGroups[0].probability.has_value());
+    REQUIRE(reproIt->outputGroups[0].items.size() == 1);
 
-    // Non-reprocessing recipes don't carry probability.
+    // The `outputs = [...]` shorthand loads as one group carrying no weight: with a single
+    // group nothing is picked, so there is nothing to weigh.
     const auto ironIngotIt = std::find_if(
         cfg.recipes.recipes.begin(), cfg.recipes.recipes.end(),
         [](const RecipeDef& r) { return r.id == "iron_ingot"; });
     REQUIRE(ironIngotIt != cfg.recipes.recipes.end());
-    REQUIRE(ironIngotIt->outputs.size() == 1);
-    REQUIRE_FALSE(ironIngotIt->outputs[0].probability.has_value());
+    REQUIRE(ironIngotIt->outputGroups.size() == 1);
+    REQUIRE(ironIngotIt->outputGroups[0].items.size() == 1);
+    REQUIRE_FALSE(ironIngotIt->outputGroups[0].probability.has_value());
 
     // ships.toml — combat ships have default_modules with a weapon; salvage ships don't.
     const auto interceptorIt = std::find_if(
@@ -390,39 +394,6 @@ duration_seconds = 1.0
         std::runtime_error);
 }
 
-TEST_CASE("Optional recipe icon field parses; absent leaves it unset", "[config]")
-{
-    TempConfigDir dir;
-    writeFile(dir.path() / "recipes.toml", R"(
-[[recipe]]
-id = "with_icon"
-building = "assembler"
-inputs = [{item = "iron_ingot", amount = 1}]
-outputs = [{item = "steel_plate", amount = 1}]
-duration_seconds = 1.0
-icon = "hardened_steel"
-
-[[recipe]]
-id = "without_icon"
-building = "assembler"
-inputs = [{item = "iron_ingot", amount = 1}]
-outputs = [{item = "copper_wire", amount = 1}]
-duration_seconds = 1.0
-)");
-
-    const RecipesConfig cfg =
-        ConfigLoader::loadRecipes((dir.path() / "recipes.toml").string());
-
-    const RecipeDef& withIcon = cfg.recipes.at(0);
-    REQUIRE(withIcon.id == "with_icon");
-    REQUIRE(withIcon.icon.has_value());
-    REQUIRE(*withIcon.icon == "hardened_steel");
-
-    const RecipeDef& withoutIcon = cfg.recipes.at(1);
-    REQUIRE(withoutIcon.id == "without_icon");
-    REQUIRE_FALSE(withoutIcon.icon.has_value());
-}
-
 // --- unlock_requires (REQ-LOCK-PREREQ) ------------------------------------
 
 namespace

src/test/ControlActionTest.cpp

@@ -0,0 +1,343 @@
+#include "catch.hpp"
+
+#include <algorithm>
+#include <vector>
+
+#include "BuildModeController.h"
+#include "BuildingType.h"
+#include "ControlAction.h"
+
+// REQ-UI-CONTROLS-ACCURACY. The panel and the input handling read one table, and these
+// tests are what makes that pay: the round-trip case below fails the moment a row is
+// shown whose binding resolves elsewhere, which is the drift the whole design exists to
+// prevent. Everything here works on action ids -- the display strings live in the ui
+// target and are not what can silently go wrong.
+
+namespace
+{
+
+ControlContext generalContext()
+{
+    return ControlContext();
+}
+
+ControlContext selectionContext(bool placeable = true)
+{
+    ControlContext context;
+    context.selection                 = ControlSelection::Buildings;
+    context.selectionCount            = 3;
+    context.placeableBuildingSelected = placeable;
+    return context;
+}
+
+ControlContext builderContext(BuildingType type)
+{
+    ControlContext context;
+    context.mode        = BuildMode::Builder;
+    context.builderType = type;
+    return context;
+}
+
+ControlContext blueprintContext(bool transfer = false)
+{
+    ControlContext context;
+    context.mode                   = BuildMode::Blueprint;
+    context.hoveredGhostIsTransfer = transfer;
+    return context;
+}
+
+ControlContext deconstructContext()
+{
+    ControlContext context;
+    context.mode = BuildMode::Deconstruct;
+    return context;
+}
+
+// A spread wide enough that every availability rule and every binding condition is
+// exercised by the whole-table properties below.
+std::vector<ControlContext> allContexts()
+{
+    ControlContext beltDragging = builderContext(BuildingType::Belt);
+    beltDragging.draggingBelt   = true;
+
+    ControlContext generalWithBlueprint            = generalContext();
+    generalWithBlueprint.temporaryBlueprintExists  = true;
+
+    ControlContext fieldSelection      = selectionContext(false);
+    fieldSelection.selection           = ControlSelection::FieldObjects;
+
+    return {generalContext(),
+            generalWithBlueprint,
+            selectionContext(),
+            fieldSelection,
+            builderContext(BuildingType::Belt),
+            builderContext(BuildingType::Assembler),
+            beltDragging,
+            blueprintContext(false),
+            blueprintContext(true),
+            deconstructContext()};
+}
+
+std::vector<ControlAction> shownActions(const ControlContext& context)
+{
+    std::vector<ControlAction> actions = getContextActions(context);
+    const std::vector<ControlAction> always = getAlwaysAvailableActions(context);
+    actions.insert(actions.end(), always.begin(), always.end());
+    return actions;
+}
+
+bool contains(const std::vector<ControlAction>& actions, ControlAction action)
+{
+    return std::find(actions.begin(), actions.end(), action) != actions.end();
+}
+
+}  // namespace
+
+TEST_CASE("ControlAction: every shown row is available", "[controls]")
+{
+    for (const ControlContext& context : allContexts())
+    {
+        for (ControlAction action : shownActions(context))
+        {
+            REQUIRE(isControlActionAvailable(action, context));
+        }
+    }
+}
+
+TEST_CASE("ControlAction: no row is shown twice", "[controls]")
+{
+    for (const ControlContext& context : allContexts())
+    {
+        std::vector<ControlAction> actions = shownActions(context);
+        std::vector<ControlAction> unique  = actions;
+        std::sort(unique.begin(), unique.end());
+        unique.erase(std::unique(unique.begin(), unique.end()), unique.end());
+        REQUIRE(unique.size() == actions.size());
+    }
+}
+
+// The core anti-drift property: a row's badges are rendered from its bindings, so every
+// binding a row advertises must actually trigger that row's action in that same context.
+TEST_CASE("ControlAction: every advertised binding resolves back to its own action",
+          "[controls]")
+{
+    for (const ControlContext& context : allContexts())
+    {
+        for (ControlAction action : shownActions(context))
+        {
+            const std::vector<ControlBinding> bindings =
+                getControlActionBindings(action, context);
+            REQUIRE_FALSE(bindings.empty());
+
+            for (const ControlBinding& binding : bindings)
+            {
+                if (binding.isMouse)
+                {
+                    REQUIRE(resolveMouseAction(binding.mouse, context) == action);
+                }
+                else
+                {
+                    REQUIRE(resolveKeyAction(binding.key, binding.modifiers, context)
+                            == action);
+                }
+            }
+        }
+    }
+}
+
+// The other direction: an input that resolves to something must resolve to an action
+// that is actually available there, so no input can trigger a no-op. This is weaker
+// than "must be a shown row" on purpose -- a context may omit an available binding
+// (Ctrl+click in the General context), which REQ-UI-CONTROLS-ACCURACY permits; what it
+// may never do is act on an unavailable one.
+TEST_CASE("ControlAction: every resolvable input is available", "[controls]")
+{
+    const std::vector<MouseBinding> mouseBindings = {
+        MouseBinding::LeftClick, MouseBinding::LeftDrag, MouseBinding::CtrlLeftClick,
+        MouseBinding::CtrlLeftDrag, MouseBinding::RightClick};
+
+    for (const ControlContext& context : allContexts())
+    {
+        for (MouseBinding binding : mouseBindings)
+        {
+            const ControlAction action = resolveMouseAction(binding, context);
+            if (action != ControlAction::None)
+            {
+                REQUIRE(isControlActionAvailable(action, context));
+            }
+        }
+
+        const std::vector<int> keys = {Qt::Key_A, Qt::Key_D, Qt::Key_W, Qt::Key_S,
+                                       Qt::Key_Space, Qt::Key_C, Qt::Key_V, Qt::Key_R,
+                                       Qt::Key_Q, Qt::Key_Escape};
+        for (int key : keys)
+        {
+            for (Qt::KeyboardModifiers modifiers :
+                 {Qt::KeyboardModifiers(Qt::NoModifier),
+                  Qt::KeyboardModifiers(Qt::ShiftModifier),
+                  Qt::KeyboardModifiers(Qt::ControlModifier)})
+            {
+                const ControlAction action = resolveKeyAction(key, modifiers, context);
+                if (action != ControlAction::None)
+                {
+                    REQUIRE(isControlActionAvailable(action, context));
+                }
+            }
+        }
+    }
+}
+
+TEST_CASE("ControlAction: contexts are named by mode and selection", "[controls]")
+{
+    REQUIRE(getControlContextKind(generalContext()) == ControlContextKind::General);
+    REQUIRE(getControlContextKind(selectionContext()) == ControlContextKind::Selection);
+    REQUIRE(getControlContextKind(builderContext(BuildingType::Belt))
+            == ControlContextKind::Build);
+    REQUIRE(getControlContextKind(blueprintContext()) == ControlContextKind::Blueprint);
+    REQUIRE(getControlContextKind(deconstructContext())
+            == ControlContextKind::Deconstruct);
+}
+
+// The three cases of Q, in the order REQ-UI-HOTKEYS evaluates them.
+TEST_CASE("ControlAction: Q leaves the active mode, else clears, else deconstructs",
+          "[controls]")
+{
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, builderContext(BuildingType::Belt))
+            == ControlAction::ExitMode);
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, blueprintContext())
+            == ControlAction::ExitMode);
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, deconstructContext())
+            == ControlAction::ExitMode);
+
+    // Whatever the selection holds: clearing it is not a buildings-only action.
+    ControlContext fieldSelection = selectionContext(false);
+    fieldSelection.selection      = ControlSelection::FieldObjects;
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, selectionContext())
+            == ControlAction::ClearSelection);
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, fieldSelection)
+            == ControlAction::ClearSelection);
+
+    // Only with nothing to clear and no mode to leave does Q enter deconstruct mode --
+    // which is what makes it two presses from a selection.
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, generalContext())
+            == ControlAction::EnterDeconstruct);
+}
+
+TEST_CASE("ControlAction: Ctrl distinguishes the chords, other modifiers do not",
+          "[controls]")
+{
+    const ControlContext context = selectionContext();
+
+    REQUIRE(resolveKeyAction(Qt::Key_C, Qt::NoModifier, context)
+            == ControlAction::CopyTemporary);
+    REQUIRE(resolveKeyAction(Qt::Key_C, Qt::ControlModifier, context)
+            == ControlAction::CreateBlueprint);
+    REQUIRE(resolveKeyAction(Qt::Key_V, Qt::ControlModifier, context)
+            == ControlAction::OpenBlueprints);
+
+    // Shift+A must still pan, as it always has -- matching modifiers exactly instead of
+    // testing Ctrl alone would silently swallow the press.
+    REQUIRE(resolveKeyAction(Qt::Key_A, Qt::ShiftModifier, context) == ControlAction::Move);
+    REQUIRE(resolveKeyAction(Qt::Key_R, Qt::ShiftModifier, blueprintContext())
+            == ControlAction::Rotate);
+}
+
+TEST_CASE("ControlAction: a transfer target turns the click into Apply settings",
+          "[controls]")
+{
+    const ControlContext plain    = blueprintContext(false);
+    const ControlContext transfer = blueprintContext(true);
+
+    REQUIRE(resolveMouseAction(MouseBinding::LeftClick, plain) == ControlAction::Place);
+    REQUIRE(resolveMouseAction(MouseBinding::LeftClick, transfer)
+            == ControlAction::ApplySettings);
+
+    REQUIRE(contains(getContextActions(plain), ControlAction::Place));
+    REQUIRE_FALSE(contains(getContextActions(plain), ControlAction::ApplySettings));
+    REQUIRE(contains(getContextActions(transfer), ControlAction::ApplySettings));
+    REQUIRE_FALSE(contains(getContextActions(transfer), ControlAction::Place));
+}
+
+TEST_CASE("ControlAction: a belt drag takes the right mouse button from ExitMode",
+          "[controls]")
+{
+    ControlContext dragging   = builderContext(BuildingType::Belt);
+    dragging.draggingBelt     = true;
+    const ControlContext idle = builderContext(BuildingType::Belt);
+
+    REQUIRE(resolveMouseAction(MouseBinding::RightClick, idle) == ControlAction::ExitMode);
+    REQUIRE(resolveMouseAction(MouseBinding::RightClick, dragging)
+            == ControlAction::CancelBeltLine);
+
+    // Q still leaves the mode outright while the drag runs, so ExitMode stays shown --
+    // with its right-click badge dropped, since the button now means something else.
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, dragging) == ControlAction::ExitMode);
+
+    const std::vector<ControlBinding> idleBindings =
+        getControlActionBindings(ControlAction::ExitMode, idle);
+    const std::vector<ControlBinding> dragBindings =
+        getControlActionBindings(ControlAction::ExitMode, dragging);
+    REQUIRE(idleBindings.size() == 2);
+    REQUIRE(dragBindings.size() == 1);
+    REQUIRE_FALSE(dragBindings.front().isMouse);
+}
+
+TEST_CASE("ControlAction: dragging a line is offered for belts only", "[controls]")
+{
+    REQUIRE(resolveMouseAction(MouseBinding::LeftDrag, builderContext(BuildingType::Belt))
+            == ControlAction::PlaceBeltLine);
+    REQUIRE(resolveMouseAction(MouseBinding::LeftDrag,
+                               builderContext(BuildingType::Assembler))
+            == ControlAction::None);
+    REQUIRE(resolveMouseAction(MouseBinding::LeftDrag, blueprintContext())
+            == ControlAction::None);
+}
+
+TEST_CASE("ControlAction: blueprint keys are offered only where they do something",
+          "[controls]")
+{
+    // V does nothing until C has captured something (REQ-UI-BLUEPRINT-TEMP).
+    ControlContext withBlueprint                  = generalContext();
+    withBlueprint.temporaryBlueprintExists        = true;
+    REQUIRE_FALSE(contains(shownActions(generalContext()), ControlAction::PasteTemporary));
+    REQUIRE(contains(shownActions(withBlueprint), ControlAction::PasteTemporary));
+    REQUIRE(resolveKeyAction(Qt::Key_V, Qt::NoModifier, generalContext())
+            == ControlAction::None);
+
+    // C and Ctrl+C need a selection holding something placeable (REQ-UI-HOTKEYS).
+    ControlContext fieldSelection = selectionContext(false);
+    fieldSelection.selection      = ControlSelection::FieldObjects;
+    REQUIRE(contains(getContextActions(selectionContext()), ControlAction::CopyTemporary));
+    REQUIRE_FALSE(contains(getContextActions(fieldSelection), ControlAction::CopyTemporary));
+    REQUIRE(resolveKeyAction(Qt::Key_C, Qt::NoModifier, fieldSelection)
+            == ControlAction::None);
+
+    // Ctrl+V opens the dialog whatever is going on (REQ-UI-HOTKEYS).
+    for (const ControlContext& context : allContexts())
+    {
+        REQUIRE(resolveKeyAction(Qt::Key_V, Qt::ControlModifier, context)
+                == ControlAction::OpenBlueprints);
+    }
+}
+
+TEST_CASE("ControlAction: selection rows appear only once something is selected",
+          "[controls]")
+{
+    const std::vector<ControlAction> general   = getContextActions(generalContext());
+    const std::vector<ControlAction> selection = getContextActions(selectionContext());
+
+    REQUIRE(contains(general, ControlAction::Select));
+    REQUIRE(contains(general, ControlAction::EnterDeconstruct));
+    REQUIRE_FALSE(contains(general, ControlAction::AddToSelection));
+    REQUIRE_FALSE(contains(general, ControlAction::CreateBlueprint));
+    REQUIRE_FALSE(contains(general, ControlAction::ClearSelection));
+
+    REQUIRE(contains(selection, ControlAction::AddToSelection));
+    REQUIRE(contains(selection, ControlAction::AddAreaToSelection));
+    REQUIRE(contains(selection, ControlAction::CreateBlueprint));
+    // Q clears here instead of entering deconstruct mode, and its row sits last, as the
+    // row that hands the context back does in every context (REQ-UI-CONTROLS-CONTENT).
+    REQUIRE(contains(selection, ControlAction::ClearSelection));
+    REQUIRE_FALSE(contains(selection, ControlAction::EnterDeconstruct));
+    REQUIRE(selection.back() == ControlAction::ClearSelection);
+}

src/test/DebrisTest.cpp

@@ -1,5 +1,6 @@
 #include "catch.hpp"
 
+#include <QRectF>
 #include <QSize>
 #include <QVector2D>
 
@@ -210,17 +211,16 @@ TEST_CASE("entityAtWorldPos never returns debris", "[debris]")
     REQUIRE((entityAtWorldPos(admin, QVector2D(3.0f, 4.0f)) == entt::null));
 }
 
-TEST_CASE("debrisInBox returns exactly the debris inside the tile rectangle", "[debris]")
+TEST_CASE("debrisInBox returns exactly the debris the box encloses", "[debris]")
 {
     EntityAdmin admin;
     DebrisSystem ss(admin);
 
-    const entt::entity inA  = ss.spawn(QVector2D(1.2f, 2.7f), 1, 100); // tile (1,2)
-    const entt::entity inB  = ss.spawn(QVector2D(4.9f, 5.1f), 1, 100); // tile (4,5)
+    const entt::entity inA  = ss.spawn(QVector2D(1.2f, 2.7f), 1, 100);
+    const entt::entity inB  = ss.spawn(QVector2D(4.9f, 5.1f), 1, 100);
     const entt::entity outX = ss.spawn(QVector2D(10.0f, 10.0f), 1, 100);
 
-    // Box given in reversed corner order to confirm normalization.
-    const std::vector<entt::entity> hit = debrisInBox(admin, QPoint(5, 5), QPoint(0, 0));
+    const std::vector<entt::entity> hit = debrisInBox(admin, QRectF(0.0, 0.0, 6.0, 6.0));
 
     REQUIRE(hit.size() == 2);
     REQUIRE(contains(hit, inA));
@@ -228,6 +228,23 @@ TEST_CASE("debrisInBox returns exactly the debris inside the tile rectangle", "[
     REQUIRE_FALSE(contains(hit, outX));
 }
 
+TEST_CASE("debrisInBox cuts within a tile, not along the tile grid", "[debris]")
+{
+    EntityAdmin admin;
+    DebrisSystem ss(admin);
+
+    const entt::entity inTile  = ss.spawn(QVector2D(1.8f, 2.5f), 1, 100);
+    // Same tile (1,2) as the piece above, but on the far side of the box's left edge:
+    // a tile-snapped box would take both (REQ-UI-MULTI-SELECT, Coverage).
+    const entt::entity outTile = ss.spawn(QVector2D(1.2f, 2.5f), 1, 100);
+
+    const std::vector<entt::entity> hit = debrisInBox(admin, QRectF(1.5, 2.0, 4.0, 4.0));
+
+    REQUIRE(hit.size() == 1);
+    REQUIRE(contains(hit, inTile));
+    REQUIRE_FALSE(contains(hit, outTile));
+}
+
 TEST_CASE("actorsInBox returns living ships and stations, excluding debris and dead actors",
           "[actor]")
 {
@@ -236,10 +253,10 @@ TEST_CASE("actorsInBox returns living ships and stations, excluding debris and d
     // Two living ships inside the box: one player, one enemy.
     const entt::entity playerShip = admin.spawnShip(
         QVector2D(1.5f, 2.5f), 100.0f, 100.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 5.0f,
-        "fighter", false);                                  // tile (1,2)
+        "fighter", false);
     const entt::entity enemyShip = admin.spawnShip(
         QVector2D(4.2f, 5.8f), 100.0f, 100.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 5.0f,
-        "raider", true);                                    // tile (4,5)
+        "raider", true);
 
     // A dead ship inside the box is excluded.
     const entt::entity deadShip = admin.spawnShip(
@@ -251,7 +268,7 @@ TEST_CASE("actorsInBox returns living ships and stations, excluding debris and d
         QVector2D(20.0f, 20.0f), 100.0f, 100.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 5.0f,
         "fighter", false);
 
-    // A station is included when any body cell lies inside the box.
+    // A station is included when the box overlaps any body cell.
     const std::vector<QPoint> stationCells{ QPoint(2, 2), QPoint(3, 2) };
     const entt::entity station = admin.spawnStation(
         QPoint(2, 2), QSize(2, 1), stationCells, 200.0f, 200.0f, true);
@@ -260,7 +277,7 @@ TEST_CASE("actorsInBox returns living ships and stations, excluding debris and d
     admin.spawnDebris(QVector2D(1.0f, 1.0f), 5, Tick(1000));
     admin.spawnHqProxy(QVector2D(0.5f, 0.5f), 500.0f, 500.0f);
 
-    const std::vector<entt::entity> hit = actorsInBox(admin, QPoint(5, 5), QPoint(0, 0));
+    const std::vector<entt::entity> hit = actorsInBox(admin, QRectF(0.0, 0.0, 6.0, 6.0));
 
     REQUIRE(hit.size() == 3);
     REQUIRE(contains(hit, playerShip));
@@ -269,3 +286,32 @@ TEST_CASE("actorsInBox returns living ships and stations, excluding debris and d
     REQUIRE_FALSE(contains(hit, deadShip));
     REQUIRE_FALSE(contains(hit, outsideShip));
 }
+
+TEST_CASE("actorsInBox takes a ship by its position and a station by its footprint",
+          "[actor]")
+{
+    EntityAdmin admin;
+
+    // Ship inside the tile the box only reaches into: taken, because the box contains
+    // its position (REQ-UI-MULTI-SELECT, Coverage).
+    const entt::entity shipInside = admin.spawnShip(
+        QVector2D(3.9f, 3.9f), 100.0f, 100.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 5.0f,
+        "fighter", false);
+    // Same tile (3,3), outside the box: a tile-snapped box would take it too.
+    const entt::entity shipOutside = admin.spawnShip(
+        QVector2D(3.1f, 3.1f), 100.0f, 100.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 5.0f,
+        "fighter", false);
+
+    // The box reaches 0.5 tiles into the station's only cell, which is enough: a
+    // station is covered when the box overlaps its footprint.
+    const std::vector<QPoint> stationCells{ QPoint(4, 3) };
+    const entt::entity station = admin.spawnStation(
+        QPoint(4, 3), QSize(1, 1), stationCells, 200.0f, 200.0f, true);
+
+    const std::vector<entt::entity> hit = actorsInBox(admin, QRectF(3.5, 3.5, 1.0, 1.0));
+
+    REQUIRE(hit.size() == 2);
+    REQUIRE(contains(hit, shipInside));
+    REQUIRE(contains(hit, station));
+    REQUIRE_FALSE(contains(hit, shipOutside));
+}

src/test/FloatingPanelPlacementTest.cpp

@@ -0,0 +1,258 @@
+#include "catch.hpp"
+
+#include <vector>
+
+#include <QRect>
+
+#include "FloatingPanelPlacement.h"
+
+// The band every case below places into: 1000x600, so a bottom edge of 599.
+static QRect makeBand()
+{
+    return QRect(0, 0, 1000, 600);
+}
+
+// The two distances the rules run on, deliberately different (REQ-UI-SELECTION-PANEL):
+// the edge margin the panel keeps from the view and from the widgets it steps around, and
+// the wider gap it keeps from the selection -- half a tile, so 20 px at a 40 px tile.
+static const int kMarginPx       = 8;
+static const int kSelectionGapPx = 20;
+
+TEST_CASE("With nothing in the way a widget may use the whole band", "[layout]")
+{
+    // REQ-UI-SELECTION-PANEL: the band's own bottom is the limit when no other floating
+    // widget has been placed yet.
+    REQUIRE(getAvailableBottomPx(makeBand(), {}, 0, 999, kMarginPx) == 599);
+}
+
+TEST_CASE("A widget in the same column pushes the bottom above it", "[layout]")
+{
+    // The build button bar sitting at the bottom center leaves the space above it, less
+    // the margin kept between the two (REQ-UI-BUILD-BAR).
+    const std::vector<QRect> occupied = { QRect(400, 520, 200, 72) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 350, 650, kMarginPx) == 511);
+}
+
+TEST_CASE("A widget beside the column does not shorten it", "[layout]")
+{
+    // The controls panel in the bottom-left corner is not in the way of a panel standing
+    // at the right edge, however tall it is (REQ-UI-CONTROLS-PANEL).
+    const std::vector<QRect> occupied = { QRect(0, 100, 200, 499) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 700, 999, kMarginPx) == 599);
+
+    // Touching columns do count as meeting: the panel starts exactly where the widget
+    // ends, which is an overlap of one pixel.
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 199, 999, kMarginPx) == 91);
+}
+
+TEST_CASE("The topmost widget in the column decides", "[layout]")
+{
+    // Several widgets meet the column: the one that reaches highest is the binding one,
+    // whatever order they are given in.
+    const std::vector<QRect> occupied = { QRect(400, 520, 200, 72),
+                                          QRect(0, 300, 500, 299),
+                                          QRect(900, 560, 100, 40) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 450, 550, kMarginPx) == 291);
+}
+
+TEST_CASE("An empty rectangle occupies nothing", "[layout]")
+{
+    // A floating widget that is hidden contributes a null rect rather than being left
+    // out of the pass.
+    const std::vector<QRect> occupied = { QRect(), QRect(400, 520, 200, 0) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 0, 999, kMarginPx) == 599);
+}
+
+TEST_CASE("A widget filling the column leaves nothing", "[layout]")
+{
+    // The caller is expected to notice that the space left is not positive rather than
+    // being handed a floor of its own.
+    const std::vector<QRect> occupied = { QRect(0, 0, 1000, 600) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 0, 999, kMarginPx) == -9);
+}
+
+// ---------------------------------------------------------------------------
+// Which side of the selection the panel takes
+// ---------------------------------------------------------------------------
+
+TEST_CASE("The panel stands to the right of the selection where it fits", "[layout]")
+{
+    // REQ-UI-SELECTION-PANEL: right of the anchor is the first choice.
+    REQUIRE(chooseSide(makeBand(), QRect(100, 100, 60, 60), 300, kSelectionGapPx)
+            == PanelSide::Right);
+}
+
+TEST_CASE("The panel goes left when the right cannot hold it", "[layout]")
+{
+    // A selection near the right edge leaves 80 px there once the gap it keeps from the
+    // selection is taken off, not enough for a 300 px panel, and the left is wide open.
+    REQUIRE(chooseSide(makeBand(), QRect(880, 100, 20, 60), 300, kSelectionGapPx)
+            == PanelSide::Left);
+}
+
+TEST_CASE("The room a side offers is measured less the gap", "[layout]")
+{
+    // A 200 px panel beside a selection whose right edge leaves 214 px to the band's: it
+    // fits there on the margin alone, but not once the wider gap is taken off.
+    const QRect anchorRect(766, 100, 20, 60);
+    REQUIRE(chooseSide(makeBand(), anchorRect, 200, kMarginPx) == PanelSide::Right);
+    REQUIRE(chooseSide(makeBand(), anchorRect, 200, kSelectionGapPx) == PanelSide::Left);
+}
+
+TEST_CASE("Fitting on neither side, the panel takes the roomier one", "[layout]")
+{
+    // A bounding box spanning most of the view: 180 px free on the left, 80 on the
+    // right, and a 300 px panel fits in neither. It covers as little as it can.
+    REQUIRE(chooseSide(makeBand(), QRect(200, 100, 700, 200), 300, kSelectionGapPx)
+            == PanelSide::Left);
+    REQUIRE(chooseSide(makeBand(), QRect(100, 100, 700, 200), 300, kSelectionGapPx)
+            == PanelSide::Right);
+}
+
+// ---------------------------------------------------------------------------
+// Where it then stands
+// ---------------------------------------------------------------------------
+
+TEST_CASE("The panel sits beside the anchor with its top edges aligned", "[layout]")
+{
+    // REQ-UI-SELECTION-PANEL: separated by the gap it keeps from the selection, growing
+    // away from it, top edge on the anchor's top edge.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 120, 60, 60),
+                                           PanelSide::Right, QSize(300, 200), {},
+                                           kSelectionGapPx, kMarginPx);
+    REQUIRE(placed == QRect(180, 120, 300, 200));
+
+    const QRect placedLeft = placeBesideAnchor(makeBand(), QRect(520, 120, 60, 60),
+                                               PanelSide::Left, QSize(300, 200), {},
+                                               kSelectionGapPx, kMarginPx);
+    REQUIRE(placedLeft == QRect(200, 120, 300, 200));
+}
+
+TEST_CASE("The gap separates the panel horizontally only", "[layout]")
+{
+    // REQ-UI-SELECTION-PANEL: widening the gap moves the panel further from the selection
+    // sideways and nowhere else -- its top stays level with the top of what it describes.
+    const QRect anchorRect(100, 120, 60, 60);
+    REQUIRE(placeBesideAnchor(makeBand(), anchorRect, PanelSide::Right, QSize(300, 200),
+                              {}, 0, kMarginPx)
+            == QRect(160, 120, 300, 200));
+    REQUIRE(placeBesideAnchor(makeBand(), anchorRect, PanelSide::Right, QSize(300, 200),
+                              {}, kSelectionGapPx, kMarginPx)
+            == QRect(180, 120, 300, 200));
+}
+
+TEST_CASE("A panel that would hang below the view is lifted", "[layout]")
+{
+    // Top-aligning with a selection low in the view would put the panel's bottom past
+    // the band, so it rises until it fits rather than overrunning it.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 500, 60, 60),
+                                           PanelSide::Right, QSize(300, 200), {},
+                                           kSelectionGapPx, kMarginPx);
+    REQUIRE(placed == QRect(180, 400, 300, 200));
+}
+
+TEST_CASE("A panel standing over another widget rises above it", "[layout]")
+{
+    // The controls panel in the bottom-left is in the way of a panel placed to the left
+    // of a selection: it clears the top of it by the edge margin, the gap from the
+    // selection having settled its left edge (REQ-UI-CONTROLS-PANEL).
+    const std::vector<QRect> occupied = { QRect(0, 300, 260, 300) };
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(500, 250, 60, 60),
+                                           PanelSide::Left, QSize(300, 200), occupied,
+                                           kSelectionGapPx, kMarginPx);
+    REQUIRE(placed == QRect(180, 92, 300, 200));
+}
+
+TEST_CASE("A panel taller than the space left is capped", "[layout]")
+{
+    // Capping is the caller's cue to scroll: it asked for 700 and got what there was.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 100, 60, 60),
+                                           PanelSide::Right, QSize(300, 700), {},
+                                           kSelectionGapPx, kMarginPx);
+    REQUIRE(placed == QRect(180, 0, 300, 600));
+}
+
+TEST_CASE("A panel that fits on neither side is pushed inside the view", "[layout]")
+{
+    // The one case where it covers part of the selection (REQ-UI-SELECTION-PANEL): it
+    // stands as far from the anchor as the band allows, not off the edge of it.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 100, 700, 200),
+                                           PanelSide::Right, QSize(300, 200), {},
+                                           kSelectionGapPx, kMarginPx);
+    REQUIRE(placed == QRect(700, 100, 300, 200));
+}
+
+// ---------------------------------------------------------------------------
+// Where it stands once the player has dragged it (REQ-UI-SELECTION-PANEL-DRAG)
+// ---------------------------------------------------------------------------
+
+TEST_CASE("A dragged panel stands where it was dropped", "[layout]")
+{
+    // With room for it there, the desired top-left corner is the answer: nothing about
+    // the selection it describes is consulted any more.
+    const QRect placed = placeAtDesiredTopLeft(makeBand(), QPoint(420, 180),
+                                               QSize(300, 200), {}, kMarginPx);
+    REQUIRE(placed == QRect(420, 180, 300, 200));
+}
+
+TEST_CASE("A panel dragged past the view's edges is pushed back inside", "[layout]")
+{
+    // Dropped off the right edge and below the bottom, it is brought back within the
+    // band, as an anchored panel is.
+    REQUIRE(placeAtDesiredTopLeft(makeBand(), QPoint(900, 500), QSize(300, 200), {},
+                                  kMarginPx)
+            == QRect(700, 400, 300, 200));
+
+    // And off the left edge and above the top, the other way.
+    REQUIRE(placeAtDesiredTopLeft(makeBand(), QPoint(-120, -60), QSize(300, 200), {},
+                                  kMarginPx)
+            == QRect(0, 0, 300, 200));
+}
+
+TEST_CASE("A dragged panel rises above the widget it was dropped over", "[layout]")
+{
+    // The player drops it over the build button bar; it lands above the bar's top by the
+    // margin instead, the bar staying where it is (REQ-UI-BUILD-BAR).
+    const std::vector<QRect> occupied = { QRect(400, 520, 200, 72) };
+    const QRect placed = placeAtDesiredTopLeft(makeBand(), QPoint(450, 480),
+                                               QSize(300, 200), occupied, kMarginPx);
+    REQUIRE(placed == QRect(450, 312, 300, 200));
+}
+
+TEST_CASE("A widget beside a dragged panel's column does not move it", "[layout]")
+{
+    // Only what the panel's own column meets is in its way: the controls panel in the
+    // bottom-left corner leaves a panel dropped at the right edge alone
+    // (REQ-UI-CONTROLS-PANEL).
+    const std::vector<QRect> occupied = { QRect(0, 300, 260, 300) };
+    const QRect placed = placeAtDesiredTopLeft(makeBand(), QPoint(600, 380),
+                                               QSize(300, 200), occupied, kMarginPx);
+    REQUIRE(placed == QRect(600, 380, 300, 200));
+}
+
+TEST_CASE("A dragged panel too tall for the room left is capped", "[layout]")
+{
+    // Capping is the caller's cue to scroll here too: a card asking for 700 px over a bar
+    // that leaves 512 px of band gets what there is, from the top of the band.
+    const std::vector<QRect> occupied = { QRect(400, 520, 200, 72) };
+    const QRect placed = placeAtDesiredTopLeft(makeBand(), QPoint(450, 100),
+                                               QSize(300, 700), occupied, kMarginPx);
+    REQUIRE(placed == QRect(450, 0, 300, 512));
+}
+
+TEST_CASE("A dragged panel returns to where it was dropped", "[layout]")
+{
+    // The resolution never writes back to the desired position: a panel lifted above the
+    // build button bar goes back to the point the player dropped it at as soon as the bar
+    // stops meeting its column -- here because the bar's button set shrank.
+    const QPoint desired(450, 380);
+    const std::vector<QRect> wideBar = { QRect(400, 520, 200, 72) };
+    REQUIRE(placeAtDesiredTopLeft(makeBand(), desired, QSize(300, 200), wideBar,
+                                  kMarginPx)
+            == QRect(450, 312, 300, 200));
+
+    const std::vector<QRect> narrowBar = { QRect(400, 520, 40, 72) };
+    REQUIRE(placeAtDesiredTopLeft(makeBand(), desired, QSize(300, 200), narrowBar,
+                                  kMarginPx)
+            == QRect(450, 380, 300, 200));
+}

src/test/ShipModuleTest.cpp

@@ -690,3 +690,31 @@ TEST_CASE("calculateShipStats: maneuvering_thrusters additive maneuvering_accele
     const float expected = (base_mpss + 10.0f) / tileSize;
     CHECK(stats.maneuveringAcceleration_tpss == Approx(expected));
 }
+
+// The precondition every entry to the layout configuration dialog checks
+// (REQ-MOD-UI-DIALOG, REQ-MOD-UI-AUTO-DIALOG, REQ-MOD-UI-PREVIEW). The empty id is the
+// one that used to slip through: "(None)" clears a shipyard and differs from whatever
+// was set, which is not the same as naming a schematic to configure.
+TEST_CASE("ShipsConfig: a layout is configurable only for a ship that has one",
+          "[modules][config]")
+{
+    const GameConfig cfg = loadTestConfig();
+
+    const ShipDef* interceptor = cfg.ships.findLayoutShipDef("interceptor");
+    REQUIRE(interceptor != nullptr);
+    CHECK(interceptor->id == "interceptor");
+    CHECK_FALSE(interceptor->layout.empty());
+
+    // The "(None)" option's id, and an id naming no ship at all.
+    CHECK(cfg.ships.findLayoutShipDef("") == nullptr);
+    CHECK(cfg.ships.findLayoutShipDef("no_such_ship") == nullptr);
+
+    // A ship that exists but defines no grid has nothing to place modules on either,
+    // where plain findShipDef still finds it.
+    ShipsConfig gridless;
+    ShipDef def;
+    def.id = "hull_only";
+    gridless.ships.push_back(def);
+    CHECK(gridless.findShipDef("hull_only") != nullptr);
+    CHECK(gridless.findLayoutShipDef("hull_only") == nullptr);
+}

src/ui/BlueprintLibrary.cpp

@@ -39,6 +39,11 @@ bool BlueprintLibrary::getCanCaptureSelection() const
     return selectionHasPlaceableBuilding(*m_sim, m_selectedBuildingIds);
 }
 
+bool BlueprintLibrary::getHasTemporaryBlueprint() const
+{
+    return m_temporaryBlueprint.has_value();
+}
+
 void BlueprintLibrary::saveSelectionAs(const QString& name)
 {
     Blueprint blueprint = createBlueprintFromSelection();

src/ui/BlueprintLibrary.h

@@ -44,6 +44,11 @@ public:
     // (REQ-UI-BLUEPRINT-CREATE).
     bool getCanCaptureSelection() const;
 
+    // True once C has captured something -- the condition under which V does anything
+    // (REQ-UI-BLUEPRINT-TEMP), and so the condition under which the controls panel
+    // offers it (REQ-UI-CONTROLS-ACCURACY).
+    bool getHasTemporaryBlueprint() const;
+
     // Captures the current selection under the given name and appends it to the list.
     // Silently does nothing when nothing player-placeable is selected.
     void saveSelectionAs(const QString& name);

src/ui/BlueprintSelectionDialog.cpp

@@ -28,6 +28,7 @@
 
 #include "Blueprint.h"
 #include "BlueprintLibrary.h"
+#include "DialogDismiss.h"
 #include "IconCaption.h"
 #include "ItemIconCache.h"
 
@@ -158,7 +159,7 @@ BlueprintSelectionDialog::BlueprintSelectionDialog(BlueprintLibrary* library,
     // Frameless: the dialog draws its own header row, so an OS title bar would only
     // repeat it (REQ-UI-BLUEPRINT-DIALOG). Square corners rather than rounded ones --
     // rounding a top-level window needs a translucent background, which is unreliable
-    // on Windows. The border matches the build bar and the side panel.
+    // on Windows. The border matches the build bar and the selection panel.
     setWindowFlags(Qt::Dialog | Qt::FramelessWindowHint);
     setAttribute(Qt::WA_StyledBackground, true);
     setStyleSheet(QStringLiteral(
@@ -236,6 +237,19 @@ std::optional<int> BlueprintSelectionDialog::getChosenIndex() const
     return m_chosenIndex;
 }
 
+void BlueprintSelectionDialog::keyPressEvent(QKeyEvent* event)
+{
+    // Q closes with no card picked, exactly as the close button does. A build mode
+    // running underneath is left alone: the dialog took the key, not the world
+    // (REQ-UI-DIALOG-DISMISS, REQ-UI-BLUEPRINT-DIALOG).
+    if (isDialogDismissKey(*event))
+    {
+        reject();
+        return;
+    }
+    QDialog::keyPressEvent(event);
+}
+
 void BlueprintSelectionDialog::rebuildGrid()
 {
     // deleteLater, not delete: this runs from a delete button's own clicked signal, and
@@ -266,9 +280,7 @@ void BlueprintSelectionDialog::rebuildGrid()
 
     // Block icon shown to the right of each cost (REQ-UI-BLUEPRINT-CARD); null when no
     // building_block icon exists, in which case the cost is the bare number.
-    const QPixmap blockIcon = m_itemIcons->hasIcon(kBlockItemId)
-        ? m_itemIcons->getPixmap(kBlockItemId, QFontMetrics(font()).height())
-        : QPixmap();
+    const QPixmap blockIcon = m_itemIcons->getInlineIcon(kBlockItemId, font());
 
     const QSize cardSize = getCardSize(font());
 

src/ui/BlueprintSelectionDialog.h

@@ -16,8 +16,8 @@ class QWidget;
 // Clicking a card accepts the dialog and reports that blueprint's index; the caller
 // enters placement mode afterwards, so the dialog is already closed by then
 // (REQ-UI-BLUEPRINT-CARD). Deleting acts on the library immediately and leaves the
-// dialog open (REQ-UI-BLUEPRINT-DELETE). Escape and the close button dismiss it with
-// no other effect.
+// dialog open (REQ-UI-BLUEPRINT-DELETE). Escape, Q, and the close button dismiss it
+// with no other effect (REQ-UI-DIALOG-DISMISS).
 class BlueprintSelectionDialog : public QDialog
 {
     Q_OBJECT
@@ -29,6 +29,9 @@ public:
 
     std::optional<int> getChosenIndex() const;
 
+protected:
+    void keyPressEvent(QKeyEvent* event) override;
+
 private:
     void rebuildGrid();
     void onCardClicked(int index);

src/ui/BuildButtonBar.cpp

@@ -2,9 +2,7 @@
 
 #include <string>
 
-#include <QByteArray>
 #include <QColor>
-#include <QFile>
 #include <QFont>
 #include <QFontMetrics>
 #include <QGuiApplication>
@@ -15,18 +13,18 @@
 #include <QPixmap>
 #include <QPushButton>
 #include <QRect>
-#include <QRegularExpression>
 #include <QSignalMapper>
 #include <QSize>
 #include <QString>
-#include <QSvgRenderer>
 
+#include "BuildingIconCache.h"
 #include "BuildingType.h"
 #include "BuildingTypeSelectedEvent.h"
 #include "DeconstructModeToggleRequestedEvent.h"
 #include "DisplayName.h"
 #include "EventManager.h"
 #include "ExitBuilderModeRequestedEvent.h"
+#include "FloatingLayoutInvalidatedEvent.h"
 #include "IconCaption.h"
 #include "InputMapper.h"
 #include "ItemIconCache.h"
@@ -54,45 +52,15 @@ namespace
     // Gap between the chip icon and the cost line on a button face.
     const int kFaceGapPx = 2;
 
-    // Rasterizes a chip SVG straight at its on-screen size times the device pixel
-    // ratio, so it stays crisp without a downscale step.
-    QPixmap renderChip(const QByteArray& svg)
-    {
-        const qreal dpr = qApp ? qApp->devicePixelRatio() : 1.0;
-        QSvgRenderer renderer(svg);
-        QPixmap pixmap(static_cast<int>(kIconSize.width()  * dpr),
-                       static_cast<int>(kIconSize.height() * dpr));
-        pixmap.setDevicePixelRatio(dpr);
-        pixmap.fill(Qt::transparent);
-        QPainter painter(&pixmap);
-        renderer.render(&painter);
-        return pixmap;
-    }
-
-    // Normal and grey-background chip pixmaps for a "<id>.svg" file. Empty pixmaps if
-    // the file cannot be read; the caller then falls back to a name caption
+    // Normal and grey-background chip pixmaps for one icon name. Empty pixmaps if the
+    // file cannot be read; the caller then falls back to a name caption
     // (REQ-UI-BUILD-ICON).
     struct ChipPixmaps { QPixmap normal; QPixmap grey; };
-    ChipPixmaps loadChipPixmaps(const QString& path)
+    ChipPixmaps loadChipPixmaps(BuildingIconCache& icons, const std::string& iconName)
     {
-        QFile file(path);
-        if (!file.open(QIODevice::ReadOnly)) { return {}; }
-        const QByteArray svg = file.readAll();
-
         ChipPixmaps result;
-        result.normal = renderChip(svg);
-
-        // Recolor only the chip background: the first "#rrggbb" fill in the file is the
-        // rounded background rect; the white glyph uses fill="none" and is left alone.
-        QString greyed = QString::fromUtf8(svg);
-        static const QRegularExpression fillPattern(QStringLiteral("fill=\"#[0-9a-fA-F]{6}\""));
-        const QRegularExpressionMatch match = fillPattern.match(greyed);
-        if (match.hasMatch())
-        {
-            greyed.replace(match.capturedStart(), match.capturedLength(),
-                           QStringLiteral("fill=\"#5f636e\""));
-        }
-        result.grey = renderChip(greyed.toUtf8());
+        result.normal = icons.getChip(iconName, kIconSize.width());
+        result.grey   = icons.getGreyChip(iconName, kIconSize.width());
         return result;
     }
 
@@ -181,18 +149,18 @@ namespace
 
 
 BuildButtonBar::BuildButtonBar(Simulation* sim, const GameConfig* config,
-                               const std::string& iconDir,
+                               BuildingIconCache* buildingIcons,
                                ItemIconCache* itemIcons, QWidget* parent)
     : QWidget(parent)
     , m_sim(sim)
     , m_config(config)
-    , m_iconDir(iconDir)
+    , m_buildingIcons(buildingIcons)
     , m_itemIcons(itemIcons)
 {
     // The bar floats over the rendered world rather than sitting in a panel, so it
     // brings its own opaque background to stay legible over any world content
     // (REQ-UI-BUILD-BAR). Palette colors keep it consistent with the buttons it holds
-    // and with the side panels; this is widget chrome, not world rendering, so it is
+    // and with the selection panel; this is widget chrome, not world rendering, so it is
     // deliberately not a visuals.toml color.
     setAttribute(Qt::WA_StyledBackground, true);
     setStyleSheet(QStringLiteral(
@@ -207,9 +175,7 @@ BuildButtonBar::BuildButtonBar(Simulation* sim, const GameConfig* config,
 
     // Block icon shown to the right of each button's cost (REQ-UI-BUILD-COST); null
     // when no building_block icon exists, in which case the cost is the bare number.
-    const QPixmap blockIcon = m_itemIcons->hasIcon(kBlockItemId)
-        ? m_itemIcons->getPixmap(kBlockItemId, QFontMetrics(font()).height())
-        : QPixmap();
+    const QPixmap blockIcon = m_itemIcons->getInlineIcon(kBlockItemId, font());
 
     for (const BuildingDef& def : config->buildings.buildings)
     {
@@ -231,13 +197,12 @@ BuildButtonBar::BuildButtonBar(Simulation* sim, const GameConfig* config,
         const QString name = (def.type == BuildingType::TunnelEntry)
             ? tr("Tunnel")
             : QString::fromStdString(toDisplayName(def.id));
+
         // Icon file name matches the building id (REQ-UI-BUILD-ICON); Tunnel Entry's
         // "tunnel_entry.svg" serves the shared Tunnel button.
-        const QString iconPath = QString::fromStdString(m_iconDir) + "/"
-            + QString::fromStdString(def.id) + ".svg";
-
         const ButtonFace face = buildButtonFace(
-            loadChipPixmaps(iconPath), InputMapper::getBuildHotkeyLabel(def.type), name,
+            loadChipPixmaps(*m_buildingIcons, def.id),
+            InputMapper::getBuildHotkeyLabel(def.type), name,
             QString::number(def.cost), blockIcon, font(), palette());
 
         QPushButton* btn = new QPushButton(this);
@@ -268,7 +233,7 @@ BuildButtonBar::BuildButtonBar(Simulation* sim, const GameConfig* config,
     // Having no cost, it shows its name where the building buttons show theirs
     // (REQ-UI-DECONSTRUCT-BUTTON), and its Q toggle as the badge (REQ-UI-HOTKEYS).
     const ButtonFace deconstructFace = buildButtonFace(
-        loadChipPixmaps(QString::fromStdString(m_iconDir) + "/deconstruct.svg"),
+        loadChipPixmaps(*m_buildingIcons, "deconstruct"),
         QStringLiteral("Q"), tr("Deconstruct"), tr("Deconstruct"), QPixmap(),
         font(), palette());
 
@@ -304,10 +269,25 @@ BuildButtonBar::~BuildButtonBar()
     unregisterForEvents();
 }
 
-void BuildButtonBar::anchorTo(const QRect& worldViewRect)
+void BuildButtonBar::placeIn(const QRect& viewRect,
+                             const std::vector<QRect>& /*occupiedRects*/)
 {
-    m_viewRect = worldViewRect;
-    recenter();
+    if (viewRect.isNull())
+    {
+        return;
+    }
+    // The layout drops hidden buttons from its size hint, but only once it has been
+    // re-run: an unlock changes which buttons are shown, and Qt would not get around to
+    // it before the bar is measured here.
+    layout()->activate();
+
+    const QSize barSize = sizeHint();
+    // Centered, except that a bar wider than the view stays flush with its left edge
+    // rather than hanging off both sides.
+    const int x = qMax(viewRect.left(),
+                       viewRect.left() + (viewRect.width() - barSize.width()) / 2);
+    const int y = viewRect.bottom() - kBottomMarginPx - barSize.height() + 1;
+    setGeometry(QRect(QPoint(x, y), barSize));
 }
 
 void BuildButtonBar::clearActiveButton()
@@ -357,29 +337,11 @@ void BuildButtonBar::updateVisibility()
     {
         m_buttons[i]->setVisible(m_sim->isBuildingUnlocked(m_types[i]));
     }
-    // A hidden button leaves the row, so the bar has to take up its new width and
-    // re-center on it (REQ-UI-BUILD-BAR).
-    recenter();
-}
-
-void BuildButtonBar::recenter()
-{
-    if (m_viewRect.isNull())
-    {
-        return;
-    }
-    // The layout drops hidden buttons from its size hint, but only once it has been
-    // re-run: updateVisibility() calls this straight after setVisible(), before Qt
-    // would get around to it on its own.
-    layout()->activate();
-
-    const QSize barSize = sizeHint();
-    // Centered, except that a bar wider than the view stays flush with its left edge
-    // rather than hanging off both sides.
-    const int x = qMax(m_viewRect.left(),
-                       m_viewRect.left() + (m_viewRect.width() - barSize.width()) / 2);
-    const int y = m_viewRect.bottom() - kBottomMarginPx - barSize.height() + 1;
-    setGeometry(QRect(QPoint(x, y), barSize));
+    // A hidden button leaves the row, so the bar takes up a new width and has to be
+    // re-centered on it -- and the widgets that keep clear of the bar have to be placed
+    // against that new rect too, so the whole pass is re-run (REQ-UI-BUILD-BAR).
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<FloatingLayoutInvalidatedEvent>());
 }
 
 void BuildButtonBar::onBuildButton(int index)

src/ui/BuildButtonBar.h

@@ -15,18 +15,22 @@
 #include "BuildingType.h"
 #include "DeconstructModeChangedEvent.h"
 #include "EventHandler.h"
+#include "FloatingPanel.h"
 #include "GameConfig.h"
 #include "UnlockedBuildingsChangedEvent.h"
 
 class QPushButton;
 class Simulation;
+class BuildingIconCache;
 class ItemIconCache;
 
 // The build menu: one horizontal row of build buttons floating over the game world
-// view (REQ-UI-BUILD-BAR). The bar is sized to its buttons; its owner hands it the
-// world view's rect through anchorTo() and it centers itself along that rect's
-// bottom edge.
+// view (REQ-UI-BUILD-BAR). The bar is sized to its buttons and centers itself along the
+// bottom edge of the rect its owner places it in. It is placed first of the floating
+// widgets and so takes the space it wants outright: nothing ever moves it aside, and the
+// widgets placed after it keep out of its way instead.
 class BuildButtonBar : public QWidget,
+                       public FloatingPanel,
                        public CombinedEventHandler<BuilderModeExitedEvent,
                                                    DeconstructModeChangedEvent,
                                                    BuildHotkeyPressedEvent,
@@ -36,20 +40,19 @@ class BuildButtonBar : public QWidget,
     Q_OBJECT
 
 public:
-    // iconDir is the directory holding the per-building "<id>.svg" chip icons
-    // (REQ-UI-BUILD-ICON), read from disk at runtime like the config files.
-    // itemIcons is the window-wide per-item icon cache and supplies the
-    // building_block icon shown in each button's cost (REQ-UI-BUILD-COST). Not
-    // owned; must outlive this widget.
+    // buildingIcons supplies each button's chip icon (REQ-UI-BUILD-ICON) and itemIcons
+    // the building_block icon shown in each button's cost (REQ-UI-BUILD-COST). Both are
+    // window-wide caches; neither is owned, and both must outlive this widget.
     BuildButtonBar(Simulation* sim, const GameConfig* config,
-                   const std::string& iconDir, ItemIconCache* itemIcons,
+                   BuildingIconCache* buildingIcons, ItemIconCache* itemIcons,
                    QWidget* parent = nullptr);
     ~BuildButtonBar() override;
 
-    // Centers the bar along the bottom edge of the game world view's rect, given in
-    // the bar's parent coordinates (REQ-UI-BUILD-BAR). The rect is remembered, so a
-    // re-center later driven by an unlock needs no second call from the owner.
-    void anchorTo(const QRect& worldViewRect);
+    // Centers the bar along the bottom edge of the game world view's rect, given in the
+    // bar's parent coordinates (REQ-UI-BUILD-BAR). Nothing is occupied yet when the bar
+    // is placed, so it ignores what it is handed there.
+    void placeIn(const QRect& viewRect,
+                 const std::vector<QRect>& occupiedRects) override;
 
     void clearActiveButton();
 
@@ -63,11 +66,6 @@ private:
     // unlock state (REQ-LOCK-BUILDING); a locked building type's button is hidden.
     void updateVisibility();
 
-    // Shrinks the bar to its currently shown buttons and re-centers it in the
-    // anchored rect (REQ-UI-BUILD-BAR). Does nothing until anchorTo() supplied that
-    // rect, so the construction-time call is harmless.
-    void recenter();
-
     void handleEvent(std::shared_ptr<const BuilderModeExitedEvent> event) override;
     void handleEvent(std::shared_ptr<const DeconstructModeChangedEvent> event) override;
     void handleEvent(std::shared_ptr<const BuildHotkeyPressedEvent> event) override;
@@ -80,12 +78,11 @@ private slots:
 private:
     Simulation*                      m_sim;
     const GameConfig*                m_config;
-    std::string                      m_iconDir;
-    ItemIconCache*                   m_itemIcons;  // Not owned; lives in MainWindow.
+    BuildingIconCache*               m_buildingIcons;  // Not owned; lives in MainWindow.
+    ItemIconCache*                   m_itemIcons;      // Not owned; lives in MainWindow.
     std::vector<BuildingType>        m_types;
     std::vector<QPushButton*>        m_buttons;
     std::map<BuildingType, int>      m_costs;
     std::optional<std::size_t>       m_activeIndex;
     QPushButton*                     m_deconstructButton;
-    QRect                            m_viewRect;
 };

src/ui/BuildingIconCache.cpp

@@ -0,0 +1,120 @@
+#include "BuildingIconCache.h"
+
+#include <QFile>
+#include <QGuiApplication>
+#include <QPainter>
+#include <QRegularExpression>
+#include <QSvgRenderer>
+
+namespace
+{
+
+// Chip background color for a build button the player cannot afford
+// (REQ-UI-BUILD-DISABLED). Part of the icon rather than of any widget's palette, so it
+// lives with the recoloring step.
+const char* const kGreyFill = "fill=\"#5f636e\"";
+
+}  // namespace
+
+
+BuildingIconCache::BuildingIconCache(const QString& iconDir)
+    : m_iconDir(iconDir)
+{
+}
+
+const QByteArray& BuildingIconCache::getSvg(const std::string& iconName)
+{
+    const std::map<std::string, QByteArray>::const_iterator cached =
+        m_svgByName.find(iconName);
+    if (cached != m_svgByName.end())
+    {
+        return cached->second;
+    }
+
+    // An absent or unreadable file caches an empty byte array so it is not retried;
+    // a missing icon is not an error (REQ-UI-BUILD-ICON).
+    QByteArray svg;
+    QFile file(m_iconDir + "/" + QString::fromStdString(iconName) + ".svg");
+    if (file.open(QIODevice::ReadOnly))
+    {
+        svg = file.readAll();
+    }
+    return m_svgByName.emplace(iconName, std::move(svg)).first->second;
+}
+
+const QByteArray& BuildingIconCache::getGreySvg(const std::string& iconName)
+{
+    const std::map<std::string, QByteArray>::const_iterator cached =
+        m_greySvgByName.find(iconName);
+    if (cached != m_greySvgByName.end())
+    {
+        return cached->second;
+    }
+
+    // Recolor only the chip background: the first "#rrggbb" fill in the file is the
+    // rounded background rect; the white glyph uses fill="none" and is left alone.
+    const QByteArray& svg = getSvg(iconName);
+    QByteArray greyed = svg;
+    if (!svg.isEmpty())
+    {
+        QString text = QString::fromUtf8(svg);
+        static const QRegularExpression fillPattern(
+            QStringLiteral("fill=\"#[0-9a-fA-F]{6}\""));
+        const QRegularExpressionMatch match = fillPattern.match(text);
+        if (match.hasMatch())
+        {
+            text.replace(match.capturedStart(), match.capturedLength(),
+                         QLatin1String(kGreyFill));
+        }
+        greyed = text.toUtf8();
+    }
+    return m_greySvgByName.emplace(iconName, std::move(greyed)).first->second;
+}
+
+bool BuildingIconCache::hasIcon(const std::string& iconName)
+{
+    return !getSvg(iconName).isEmpty();
+}
+
+QPixmap BuildingIconCache::getChip(const std::string& iconName, int sizePx)
+{
+    return getPixmap(iconName, getSvg(iconName), sizePx);
+}
+
+QPixmap BuildingIconCache::getGreyChip(const std::string& iconName, int sizePx)
+{
+    return getPixmap("grey:" + iconName, getGreySvg(iconName), sizePx);
+}
+
+QPixmap BuildingIconCache::getPixmap(const std::string& cacheKey,
+                                     const QByteArray& svg, int sizePx)
+{
+    if (sizePx <= 0)
+    {
+        return QPixmap();
+    }
+
+    const std::pair<std::string, int> key(cacheKey, sizePx);
+    const std::map<std::pair<std::string, int>, QPixmap>::const_iterator cached =
+        m_pixmapCache.find(key);
+    if (cached != m_pixmapCache.end())
+    {
+        return cached->second;
+    }
+
+    QPixmap pixmap;
+    if (!svg.isEmpty())
+    {
+        // Rasterized straight at its on-screen size times the device pixel ratio, so it
+        // stays crisp without a downscale step.
+        const qreal dpr = qApp ? qApp->devicePixelRatio() : 1.0;
+        QSvgRenderer renderer(svg);
+        pixmap = QPixmap(static_cast<int>(sizePx * dpr), static_cast<int>(sizePx * dpr));
+        pixmap.setDevicePixelRatio(dpr);
+        pixmap.fill(Qt::transparent);
+        QPainter painter(&pixmap);
+        painter.setRenderHint(QPainter::Antialiasing, true);
+        renderer.render(&painter);
+    }
+    return m_pixmapCache.emplace(key, std::move(pixmap)).first->second;
+}

src/ui/BuildingIconCache.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include <map>
+#include <string>
+#include <utility>
+
+#include <QByteArray>
+#include <QPixmap>
+#include <QString>
+
+// Rasterizes and caches the per-building chip SVGs (REQ-UI-BUILD-ICON). A chip is a
+// rounded colored background bearing a white line glyph, loaded from a directory with
+// one file per building named after the building's id (e.g. "belt.svg"). Shared by the
+// build button bar and the selection panel's card header (REQ-UI-SELECTION-CARD) so the
+// rasterization is not duplicated.
+//
+// A missing icon file is not an error: hasIcon() returns false for it and the caller
+// falls back (a name caption on a build button, a bare title in the panel header).
+class BuildingIconCache
+{
+public:
+    // iconDir is the directory holding the "<id>.svg" chip files (typically
+    // "<configDir>/../icons/buildings").
+    explicit BuildingIconCache(const QString& iconDir);
+
+    // True if a chip SVG file exists for the given icon name. Loads the file's bytes on
+    // first query and remembers the result (including absence) so repeated calls are
+    // cheap. The name is a building id for the building buttons, but need not be one --
+    // the Deconstruct button's "deconstruct" chip goes through the same path.
+    bool hasIcon(const std::string& iconName);
+
+    // The chip rasterized to a transparent sizePx*sizePx pixmap at the device pixel
+    // ratio, cached per (name, size). Returns a null pixmap when the file is missing.
+    QPixmap getChip(const std::string& iconName, int sizePx);
+
+    // As getChip(), but with the chip background recolored grey and the glyph left
+    // alone, for a build button the player cannot currently afford
+    // (REQ-UI-BUILD-DISABLED).
+    QPixmap getGreyChip(const std::string& iconName, int sizePx);
+
+private:
+    // Raw SVG bytes for an icon name, loading and caching them on first access. An
+    // absent file caches an empty QByteArray so it is not retried.
+    const QByteArray& getSvg(const std::string& iconName);
+    // The same SVG with its background fill replaced by grey, cached alongside.
+    const QByteArray& getGreySvg(const std::string& iconName);
+    // Shared rasterize-and-cache step. cacheKey distinguishes the normal and grey
+    // variants of one icon name within the single pixmap cache.
+    QPixmap getPixmap(const std::string& cacheKey, const QByteArray& svg, int sizePx);
+
+    QString                           m_iconDir;
+    std::map<std::string, QByteArray> m_svgByName;
+    std::map<std::string, QByteArray> m_greySvgByName;
+    std::map<std::pair<std::string, int>, QPixmap> m_pixmapCache;
+};

src/ui/CMakeLists.txt

@@ -1,3 +1,5 @@
+add_subdirectory(selection)
+
 SET(HDRS
     ${HDRS}
     ${CMAKE_CURRENT_SOURCE_DIR}/VisualsConfig.h
@@ -10,9 +12,13 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldPrimitives.h
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldRenderer.h
     ${CMAKE_CURRENT_SOURCE_DIR}/HeaderBar.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/FloatingPanel.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildButtonBar.h
-    ${CMAKE_CURRENT_SOURCE_DIR}/SelectedBuildingPanel.h
-    ${CMAKE_CURRENT_SOURCE_DIR}/FieldSelectionPanel.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/SelectionPanel.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/SelectionBounds.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlsPanel.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlActionText.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/DialogDismiss.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintLibrary.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSelectionDialog.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipLayoutDialog.h
@@ -20,12 +26,20 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipStatsPanel.h
     ${CMAKE_CURRENT_SOURCE_DIR}/SchematicChoiceDialog.h
     ${CMAKE_CURRENT_SOURCE_DIR}/RecipeSelectionDialog.h
-    ${CMAKE_CURRENT_SOURCE_DIR}/RecipeTooltip.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/RecipeLineRow.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/OptionButton.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ItemProducers.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ItemIconCache.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/BuildingIconCache.h
     ${CMAKE_CURRENT_SOURCE_DIR}/IconCaption.h
     PARENT_SCOPE
 )
 
+set(UI_INCLUDE_PATH
+    ${UI_INCLUDE_PATH}
+    PARENT_SCOPE
+)
+
 SET(SRCS
     ${SRCS}
     ${CMAKE_CURRENT_SOURCE_DIR}/VisualsLoader.cpp
@@ -37,8 +51,10 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldRenderer.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/HeaderBar.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildButtonBar.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/SelectedBuildingPanel.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/FieldSelectionPanel.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/SelectionPanel.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/SelectionBounds.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlsPanel.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlActionText.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintLibrary.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSelectionDialog.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipLayoutDialog.cpp
@@ -46,8 +62,11 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipStatsPanel.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/SchematicChoiceDialog.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/RecipeSelectionDialog.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/RecipeTooltip.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/RecipeLineRow.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/OptionButton.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ItemProducers.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ItemIconCache.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/BuildingIconCache.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/IconCaption.cpp
     PARENT_SCOPE
 )

src/ui/ControlActionText.cpp

@@ -0,0 +1,93 @@
+#include "ControlActionText.h"
+
+#include <QCoreApplication>
+#include <QKeySequence>
+
+namespace
+{
+
+// tr() for a file of free functions. Q_DECLARE_TR_FUNCTIONS expands with access
+// specifiers, so it needs a class rather than a namespace; this struct exists only to
+// carry it and give the strings a single lupdate context.
+struct Strings
+{
+    Q_DECLARE_TR_FUNCTIONS(ControlActionText)
+};
+
+QString getMouseBadge(MouseBinding binding)
+{
+    switch (binding)
+    {
+    case MouseBinding::LeftClick:     return Strings::tr("LMB");
+    case MouseBinding::LeftDrag:      return Strings::tr("LMB drag");
+    case MouseBinding::CtrlLeftClick: return Strings::tr("Ctrl+LMB");
+    case MouseBinding::CtrlLeftDrag:  return Strings::tr("Ctrl+LMB drag");
+    case MouseBinding::RightClick:    return Strings::tr("RMB");
+    }
+    return QString();
+}
+
+}  // namespace
+
+QString getControlBindingBadge(const ControlBinding& binding)
+{
+    if (binding.isMouse) { return getMouseBadge(binding.mouse); }
+
+    // QKeySequence spells the modifiers and the key together and localizes them, which
+    // is what makes this stay correct once keys are rebindable: the chip is generated
+    // from the binding rather than typed next to it.
+    return QKeySequence(binding.key | static_cast<int>(binding.modifiers))
+        .toString(QKeySequence::NativeText);
+}
+
+QString getControlActionLabel(ControlAction action, const ControlContext& context)
+{
+    switch (action)
+    {
+    case ControlAction::None:               return QString();
+    case ControlAction::Move:               return Strings::tr("Move");
+    case ControlAction::GameSpeed:          return Strings::tr("Game speed");
+    case ControlAction::TogglePause:        return Strings::tr("Toggle pause");
+    case ControlAction::PasteTemporary:     return Strings::tr("Paste last");
+    case ControlAction::OpenBlueprints:     return Strings::tr("Blueprints");
+    case ControlAction::OpenMenu:           return Strings::tr("Menu");
+    // A click on empty space clears and a click on an object replaces; naming only the
+    // first would be a half-truth once something is selected.
+    case ControlAction::Select:
+        return context.selection == ControlSelection::None
+                   ? Strings::tr("Select")
+                   : Strings::tr("Select / clear selection");
+    case ControlAction::SelectArea:         return Strings::tr("Select area");
+    case ControlAction::AddToSelection:     return Strings::tr("Add / remove from selection");
+    case ControlAction::AddAreaToSelection: return Strings::tr("Add area to selection");
+    case ControlAction::EnterDeconstruct:   return Strings::tr("Deconstruct mode");
+    case ControlAction::CopyTemporary:      return Strings::tr("Copy to temporary blueprint");
+    case ControlAction::CreateBlueprint:    return Strings::tr("Create blueprint");
+    case ControlAction::ClearSelection:     return Strings::tr("Clear selection");
+    case ControlAction::Place:              return Strings::tr("Place");
+    case ControlAction::ApplySettings:      return Strings::tr("Apply settings");
+    case ControlAction::PlaceBeltLine:      return Strings::tr("Place belt line");
+    case ControlAction::Rotate:             return Strings::tr("Rotate");
+    case ControlAction::CancelBeltLine:     return Strings::tr("Cancel belt line");
+    case ControlAction::ExitMode:
+        return context.mode == BuildMode::Deconstruct
+                   ? Strings::tr("Exit deconstruct mode")
+                   : Strings::tr("Exit placement");
+    case ControlAction::ToggleDeconstruct:  return Strings::tr("Toggle deconstruct");
+    case ControlAction::DeconstructArea:    return Strings::tr("Deconstruct area");
+    }
+    return QString();
+}
+
+QString getControlContextName(ControlContextKind kind)
+{
+    switch (kind)
+    {
+    case ControlContextKind::General:     return Strings::tr("GENERAL");
+    case ControlContextKind::Selection:   return Strings::tr("SELECTION");
+    case ControlContextKind::Build:       return Strings::tr("BUILD MODE");
+    case ControlContextKind::Blueprint:   return Strings::tr("BLUEPRINT MODE");
+    case ControlContextKind::Deconstruct: return Strings::tr("DECONSTRUCT MODE");
+    }
+    return QString();
+}

src/ui/ControlActionText.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <QString>
+
+#include "ControlAction.h"
+
+// What the player is shown for the actions and bindings declared in ControlAction.h
+// (REQ-UI-CONTROLS-CONTENT). Kept out of lib/core deliberately: that file decides what
+// is available and what triggers it, this one decides what it is called, and only this
+// half is presentation.
+//
+// A badge is rendered from the binding it belongs to rather than written beside it, so
+// what the panel shows on a chip is what the resolver actually matches. When bindings
+// become player-configurable, this is the only place that has to learn to spell a
+// rebound key.
+
+// The chip text for one binding: "Ctrl+V", "LMB drag", "RMB".
+QString getControlBindingBadge(const ControlBinding& binding);
+
+// What the action is called in this context. A few actions are named for their
+// situation rather than their implementation -- one exit action reads "Exit placement"
+// in a placement mode and "Exit deconstruct mode" in deconstruct mode.
+QString getControlActionLabel(ControlAction action, const ControlContext& context);
+
+// The heading, in the upper case the card shows it in (REQ-UI-CONTROLS-CARD).
+QString getControlContextName(ControlContextKind kind);

src/ui/ControlsPanel.cpp

@@ -0,0 +1,343 @@
+#include "ControlsPanel.h"
+
+#include <QFont>
+#include <QFrame>
+#include <QHBoxLayout>
+#include <QLabel>
+#include <QMouseEvent>
+#include <QScrollArea>
+#include <QScrollBar>
+#include <QTimer>
+#include <QVBoxLayout>
+
+#include "ControlActionText.h"
+#include "EventManager.h"
+#include "FloatingLayoutInvalidatedEvent.h"
+#include "FloatingPanelPlacement.h"
+#include "GameWorldView.h"
+#include "selection/SelectionNames.h"
+
+namespace
+{
+
+const int kMarginPx      = 8;   // between the view's edge and the panel
+const int kCardMarginPx  = 8;   // inside the panel, around its content
+const int kHeadingGapPx  = 4;   // between the heading and the rows
+const int kRefreshMs     = 50;  // see the class comment on why this polls
+
+// The panel's border, from the stylesheet below. Spelled out because the stylesheet box
+// is what sets it and asking the style for it before the first show is unreliable.
+const int kBorderPx = 1;
+
+// Separates the heading's name from its detail, e.g. "BUILD MODE * Assembler".
+const QChar kHeadingSeparator(0x00B7);  // U+00B7 MIDDLE DOT
+
+// The upper-case heading and caption are tracked out a little so they read as labels
+// rather than as words. Set on the font because Qt's stylesheets have no letter-spacing
+// property -- writing one there is silently ignored apart from a warning per widget.
+QFont makeSpacedFont(QFont font, bool bold, int pointSizeDelta)
+{
+    font.setBold(bold);
+    if (pointSizeDelta != 0 && font.pointSize() > 0)
+    {
+        font.setPointSize(qMax(1, font.pointSize() + pointSizeDelta));
+    }
+    font.setLetterSpacing(QFont::AbsoluteSpacing, 1.0);
+    return font;
+}
+
+// One row: the chips for the bindings, then what the action is called. Built as a plain
+// widget rather than a class of its own -- it holds no state and answers no questions.
+QWidget* makeRow(ControlAction action, const ControlContext& context, QWidget* parent)
+{
+    QWidget*     row    = new QWidget(parent);
+    QHBoxLayout* layout = new QHBoxLayout(row);
+    layout->setContentsMargins(0, 2, 0, 2);
+    layout->setSpacing(4);
+
+    // Every badge is rendered from the binding the resolver matches, so a chip cannot
+    // claim a key that does nothing (REQ-UI-CONTROLS-ACCURACY). The chips of the row
+    // that leaves the context are the ones marked, not its label (REQ-UI-CONTROLS-CARD):
+    // leaving a build mode and clearing the selection are the same gesture to the player,
+    // one key that hands the context back, so they are marked alike.
+    const bool backsOut = (action == ControlAction::ExitMode
+                           || action == ControlAction::ClearSelection);
+    const std::vector<ControlBinding> bindings = getControlActionBindings(action, context);
+    for (const ControlBinding& binding : bindings)
+    {
+        QLabel* badge = new QLabel(getControlBindingBadge(binding), row);
+        badge->setObjectName(backsOut ? QStringLiteral("controlBadgeExit")
+                                      : QStringLiteral("controlBadge"));
+        layout->addWidget(badge);
+    }
+
+    QLabel* label = new QLabel(getControlActionLabel(action, context), row);
+    label->setObjectName(QStringLiteral("controlLabel"));
+    layout->addSpacing(4);
+    layout->addWidget(label);
+    layout->addStretch(1);
+    return row;
+}
+
+// Adds a freshly built widget to the rows and shows it.
+//
+// The show is what makes it count. A widget created under an already-visible parent
+// starts hidden, and a layout treats a hidden item as empty -- it contributes nothing
+// to the size hint until something shows it, which otherwise does not happen until the
+// event loop next runs, long after the panel has measured itself.
+void addAndShow(QVBoxLayout* layout, QWidget* widget)
+{
+    layout->addWidget(widget);
+    widget->show();
+}
+
+}  // namespace
+
+ControlsPanel::ControlsPanel(const GameWorldView* view, QWidget* parent)
+    : QWidget(parent)
+    , m_view(view)
+{
+    // Floats over the rendered world, so it brings its own background to stay legible
+    // over any world content (REQ-UI-CONTROLS-PANEL). Palette colors match the build
+    // button bar's and the selection panel's chrome; like them this is widget chrome
+    // rather than world rendering, so it is deliberately not a visuals.toml color. The
+    // class scoped selector keeps the border on the panel rather than cascading onto
+    // its children.
+    setAttribute(Qt::WA_StyledBackground, true);
+    // Letter spacing is deliberately absent here: Qt's stylesheet syntax has no such
+    // property and warns on every widget it is applied to. The heading and the caption
+    // set it on their QFont instead.
+    setStyleSheet(QStringLiteral(
+        "ControlsPanel { background-color: palette(window);"
+        " border: 1px solid palette(mid); border-radius: 4px; }"
+        "QLabel#controlHeading { color: palette(text); }"
+        "QLabel#controlBadge { border: 1px solid palette(mid); border-radius: 3px;"
+        " padding: 1px 5px; font-family: monospace; color: palette(text); }"
+        "QLabel#controlLabel { color: palette(text); }"
+        // The row that leaves the mode is marked on its chips rather than its label
+        // (REQ-UI-CONTROLS-CARD): the label keeps the ordinary text color, so the row
+        // stays legible whatever the palette, and only the chips carry the warning.
+        //
+        // A literal red because there is no palette role for "destructive" -- the
+        // nearest, bright-text, is white by design, being meant for text over dark
+        // highlights, and was unreadable on this panel's chrome. This value reads on a
+        // light and a dark background alike. It is widget chrome, so like the rest of
+        // this stylesheet it is deliberately not a visuals.toml color.
+        "QLabel#controlBadgeExit { border: 1px solid #c0392b; border-radius: 3px;"
+        " padding: 1px 5px; font-family: monospace; color: #c0392b; }"
+        "QLabel#controlCaption { color: palette(mid); }"));
+
+    QVBoxLayout* outerLayout = new QVBoxLayout(this);
+    outerLayout->setContentsMargins(kCardMarginPx, kCardMarginPx,
+                                    kCardMarginPx, kCardMarginPx);
+    outerLayout->setSpacing(kHeadingGapPx);
+
+    m_heading = new QLabel(this);
+    m_heading->setObjectName(QStringLiteral("controlHeading"));
+    m_heading->setCursor(Qt::PointingHandCursor);
+    m_heading->setFont(makeSpacedFont(font(), /*bold*/ true, /*pointSizeDelta*/ 0));
+    outerLayout->addWidget(m_heading);
+
+    // Rows taller than the space available scroll rather than being cut off
+    // (REQ-UI-CONTROLS-PANEL). The viewport is transparent so the panel's own rounded
+    // chrome shows through, and horizontal scrolling is off because the width always
+    // follows the content.
+    m_rows       = new QWidget(this);
+    m_rowsLayout = new QVBoxLayout(m_rows);
+    m_rowsLayout->setContentsMargins(0, 0, 0, 0);
+    m_rowsLayout->setSpacing(0);
+    m_rows->setAutoFillBackground(false);
+
+    m_scrollArea = new QScrollArea(this);
+    m_scrollArea->setFrameShape(QFrame::NoFrame);
+    m_scrollArea->setWidgetResizable(true);
+    m_scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    m_scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
+    m_scrollArea->viewport()->setAutoFillBackground(false);
+    m_scrollArea->setWidget(m_rows);
+    outerLayout->addWidget(m_scrollArea);
+
+    // Polling rather than subscribing; see the class comment.
+    m_refreshTimer = new QTimer(this);
+    connect(m_refreshTimer, &QTimer::timeout, this, &ControlsPanel::refresh);
+    m_refreshTimer->start(kRefreshMs);
+
+    refresh();
+}
+
+void ControlsPanel::invalidateLayout()
+{
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<FloatingLayoutInvalidatedEvent>());
+}
+
+void ControlsPanel::mousePressEvent(QMouseEvent* event)
+{
+    // Only the heading toggles; a click anywhere else is swallowed so it never reaches
+    // the world beneath (REQ-UI-CONTROLS-PANEL).
+    if (m_heading->geometry().contains(event->pos()))
+    {
+        m_collapsed = !m_collapsed;
+        m_scrollArea->setVisible(!m_collapsed);
+        invalidateLayout();
+    }
+    event->accept();
+}
+
+void ControlsPanel::refresh()
+{
+    if (!m_view) { return; }
+
+    const ControlContext context = m_view->getControlContext();
+
+    const QString                    heading = getHeadingText(context);
+    const std::vector<ControlAction> contextActions = getContextActions(context);
+    const std::vector<ControlAction> alwaysActions  = getAlwaysAvailableActions(context);
+
+    if (heading == m_shownHeading && contextActions == m_shownContextActions
+        && alwaysActions == m_shownAlwaysActions)
+    {
+        return;
+    }
+
+    m_shownHeading        = heading;
+    m_shownContextActions = contextActions;
+    m_shownAlwaysActions  = alwaysActions;
+    rebuild(context);
+}
+
+void ControlsPanel::rebuild(const ControlContext& context)
+{
+    m_heading->setText(m_shownHeading);
+
+    // Rows are rebuilt wholesale rather than reconciled: a context change replaces
+    // nearly all of them, and the panel redraws only when something actually changed.
+    while (QLayoutItem* item = m_rowsLayout->takeAt(0))
+    {
+        delete item->widget();
+        delete item;
+    }
+
+    for (ControlAction action : m_shownContextActions)
+    {
+        addAndShow(m_rowsLayout, makeRow(action, context, m_rows));
+    }
+
+    // The always-available block sits under a divider in every context, the General one
+    // included, so the card is read the same way wherever the player is
+    // (REQ-UI-CONTROLS-CARD).
+    if (!m_shownAlwaysActions.empty())
+    {
+        QFrame* divider = new QFrame(m_rows);
+        divider->setFrameShape(QFrame::HLine);
+        divider->setFrameShadow(QFrame::Plain);
+        m_rowsLayout->addSpacing(6);
+        addAndShow(m_rowsLayout, divider);
+
+        QLabel* caption = new QLabel(tr("ALWAYS AVAILABLE"), m_rows);
+        caption->setObjectName(QStringLiteral("controlCaption"));
+        caption->setFont(makeSpacedFont(font(), /*bold*/ false, /*pointSizeDelta*/ -1));
+        addAndShow(m_rowsLayout, caption);
+    }
+
+    for (ControlAction action : m_shownAlwaysActions)
+    {
+        addAndShow(m_rowsLayout, makeRow(action, context, m_rows));
+    }
+
+    m_scrollArea->setVisible(!m_collapsed);
+    invalidateLayout();
+}
+
+QString ControlsPanel::getHeadingText(const ControlContext& context) const
+{
+    const ControlContextKind kind = getControlContextKind(context);
+    const QString            name = getControlContextName(kind);
+
+    QString detail;
+    switch (kind)
+    {
+    case ControlContextKind::Build:
+        detail = getBuildingTypeName(context.builderType);
+        break;
+    case ControlContextKind::Blueprint:
+    {
+        // The temporary blueprint is never named (REQ-UI-BLUEPRINT-TEMP), so it is
+        // labelled by what it is rather than left blank.
+        const QString blueprintName = m_view->getActiveBlueprintName();
+        detail = blueprintName.isEmpty() ? tr("Temporary") : blueprintName;
+        break;
+    }
+    case ControlContextKind::Selection:
+        detail = context.selection == ControlSelection::Buildings
+                     ? tr("%n building(s)", "", context.selectionCount)
+                     : tr("%n object(s)", "", context.selectionCount);
+        break;
+    case ControlContextKind::General:
+    case ControlContextKind::Deconstruct:
+        break;
+    }
+
+    if (detail.isEmpty()) { return name; }
+    return name + QStringLiteral(" ") + kHeadingSeparator + QStringLiteral(" ") + detail;
+}
+
+void ControlsPanel::placeIn(const QRect& viewRect, const std::vector<QRect>& occupiedRects)
+{
+    if (viewRect.isNull()) { return; }
+
+    // Rows are torn down and rebuilt wholesale, and a widget added to a layout is only
+    // shown once that layout runs -- without this the new rows count for nothing and
+    // the card is measured for the context before it. The polish belongs to the same
+    // step: a freshly created label reports an unstyled size hint until the stylesheet
+    // has reached it, and the badge chips carry border and padding that change it.
+    m_rows->ensurePolished();
+    m_rowsLayout->invalidate();
+    m_rowsLayout->activate();
+
+    const QRect band = viewRect.adjusted(kMarginPx, kMarginPx, -kMarginPx, -kMarginPx);
+    if (band.width() <= 0 || band.height() <= 0) { return; }
+
+    // Measured from the heading and the rows directly rather than from the panel's own
+    // layout: the rows now sit in a scroll area, whose size hint describes a viewport
+    // and says nothing about how tall its contents are. Deliberately not activating the
+    // panel's own layout either -- that lays its children out inside the geometry left
+    // over from the previous context, which is the wrong frame of reference for
+    // choosing the new one. setGeometry below re-runs it.
+    const int   chromePx    = 2 * (kCardMarginPx + kBorderPx);
+    const QSize headingHint = m_heading->sizeHint();
+    const QSize rowsHint    = m_rows->sizeHint();
+
+    int contentWidthPx  = headingHint.width();
+    int contentHeightPx = headingHint.height();
+    if (!m_collapsed)
+    {
+        contentWidthPx  = qMax(contentWidthPx, rowsHint.width());
+        contentHeightPx += kHeadingGapPx + rowsHint.height();
+    }
+    const int wantedHeightPx = contentHeightPx + chromePx;
+
+    // The bottom-left corner of the view, growing upward as rows are added
+    // (REQ-UI-CONTROLS-PANEL).
+    int widthPx = qMin(contentWidthPx + chromePx, band.width());
+
+    // The build button bar is centered and sized to its buttons, so it usually leaves
+    // this corner free and the panel can share the bottom edge with it. Only where the
+    // two would actually meet does the panel rise, clearing the bar's top by the same
+    // margin it keeps from the view's edges (REQ-UI-BUILD-BAR). The bar is the only
+    // widget placed before this one, so it is the only rect that can be in the way.
+    const int bottomPx = getAvailableBottomPx(band, occupiedRects, band.left(),
+                                              band.left() + widthPx - 1, kMarginPx);
+    int heightPx = qMin(wantedHeightPx, qMax(0, bottomPx - band.top() + 1));
+    int topPx    = bottomPx - heightPx + 1;
+
+    // Whatever the rows lost to either cap, they scroll for. The scrollbar needs its
+    // own width, or it would appear over the labels.
+    if (heightPx < wantedHeightPx)
+    {
+        widthPx = qMin(widthPx + m_scrollArea->verticalScrollBar()->sizeHint().width(),
+                       band.width());
+    }
+
+    setGeometry(band.left(), topPx, widthPx, heightPx);
+}

src/ui/ControlsPanel.h

@@ -0,0 +1,87 @@
+#pragma once
+
+#include <vector>
+
+#include <QRect>
+#include <QString>
+#include <QWidget>
+
+#include "ControlAction.h"
+#include "FloatingPanel.h"
+
+class GameWorldView;
+class QLabel;
+class QScrollArea;
+class QTimer;
+class QVBoxLayout;
+
+// Shows the controls available in the player's current situation
+// (REQ-UI-CONTROLS-PANEL). The panel decides nothing: which rows apply is
+// ControlAction.h's answer, the same one the key handling and the world view's mouse
+// dispatch act on, so what is shown and what happens cannot part company
+// (REQ-UI-CONTROLS-ACCURACY).
+//
+// It floats over the game world at the left edge, bottom-aligned within the band its
+// owner hands it, and collapses to its heading when the heading is clicked.
+//
+// Refreshed on a timer rather than by subscribing to events: two of the things that
+// change a row -- a belt drag starting, the ghost moving over a transfer target --
+// happen on mouse movement and publish nothing, and they still have to be reflected
+// while the game is paused, so there is no tick to hang it on either. The rebuild is
+// skipped unless the resolved content actually differs, which is a vector of enums to
+// compare.
+class ControlsPanel : public QWidget, public FloatingPanel
+{
+    Q_OBJECT
+
+public:
+    // Neither pointer is owned; both must outlive this widget. The view is the source
+    // of the control context, being the widget that owns the build mode and the
+    // selection.
+    ControlsPanel(const GameWorldView* view, QWidget* parent = nullptr);
+
+    // Places the panel in the bottom-left corner of the game world view. It shares the
+    // bottom edge with the build button bar rather than clearing its strip, the bar
+    // being centered and sized to its buttons and so usually leaving the left free; it
+    // rises above the bar only when the two would otherwise overlap
+    // (REQ-UI-CONTROLS-PANEL, REQ-UI-BUILD-BAR). The bar is the only thing placed before
+    // it, so it is the only rect it ever has to rise above.
+    void placeIn(const QRect& viewRect,
+                 const std::vector<QRect>& occupiedRects) override;
+
+protected:
+    // Clicking the heading collapses and expands the panel (REQ-UI-CONTROLS-PANEL).
+    void mousePressEvent(QMouseEvent* event) override;
+
+private:
+    // Re-resolves the context and rebuilds only if the rows or the heading changed.
+    void refresh();
+    // Replaces the rows with those of the current context.
+    void rebuild(const ControlContext& context);
+    // The heading's "<name> * <detail>" text for the context, detail omitted when the
+    // context has none.
+    QString getHeadingText(const ControlContext& context) const;
+    // Asks for the placement pass to be re-run, the panel's own size having changed.
+    void invalidateLayout();
+
+    const GameWorldView* m_view;
+
+    QLabel*      m_heading;
+    // Scrolls the rows once they outgrow the space the panel has (REQ-UI-CONTROLS-PANEL).
+    // The heading is deliberately outside it, so it stays put and stays clickable.
+    QScrollArea* m_scrollArea;
+    QWidget*     m_rows;
+    QVBoxLayout* m_rowsLayout;
+    QTimer*      m_refreshTimer;
+
+    // What is currently drawn, so a refresh that resolves to the same thing does
+    // nothing. The always-available block is kept separately because the divider
+    // between the two is part of what is drawn.
+    QString                    m_shownHeading;
+    std::vector<ControlAction> m_shownContextActions;
+    std::vector<ControlAction> m_shownAlwaysActions;
+
+    // Survives context changes and simulation restarts; presentation only, never a
+    // command (REQ-UI-CONTROLS-PANEL).
+    bool m_collapsed = false;
+};

src/ui/DialogDismiss.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <QKeyEvent>
+#include <Qt>
+
+// REQ-UI-DIALOG-DISMISS: Q dismisses an open dialog, beside the Escape that QDialog
+// already handles. The key is spelled here rather than in each dialog's key handler, so
+// the dialogs that take it cannot drift apart from one another.
+//
+// Ctrl must not be held, matching how the game world's table separates a chord from the
+// bare key (resolveKeyAction in lib/core/ControlAction.cpp). This deliberately stays out
+// of that table: the table answers what an input does in the player's current situation,
+// and a dialog has no situation -- it holds focus and takes the key whatever the world
+// beneath it is doing.
+inline bool isDialogDismissKey(const QKeyEvent& event)
+{
+    return event.key() == Qt::Key_Q
+           && (event.modifiers() & Qt::ControlModifier) == 0;
+}

src/ui/FieldSelectionPanel.cpp

@@ -1,403 +0,0 @@
-#include "FieldSelectionPanel.h"
-
-#include <algorithm>
-#include <map>
-#include <string>
-
-#include <QFont>
-#include <QLabel>
-#include <QStringList>
-#include <QVBoxLayout>
-
-#include "DebrisSystem.h"
-#include "DisplayName.h"
-#include "EntityAdmin.h"
-#include "FactionComponent.h"
-#include "GameConfig.h"
-#include "HealthComponent.h"
-#include "ModuleOwnerComponent.h"
-#include "SelectedBehaviorComponent.h"
-#include "ShipIdentityComponent.h"
-#include "ShipStatsCalculator.h"
-#include "ShipStatsPanel.h"
-#include "Simulation.h"
-#include "StationBodyComponent.h"
-#include "ThreatCostCalculator.h"
-#include "WeaponComponent.h"
-
-
-FieldSelectionPanel::FieldSelectionPanel(Simulation* sim,
-                                         const GameConfig* config,
-                                         QWidget* parent)
-    : QWidget(parent)
-    , m_sim(sim)
-    , m_config(config)
-{
-    // Zero margins and the same spacing as the enclosing SelectedBuildingPanel layout, so
-    // nesting the field widgets in this panel leaves their geometry unchanged.
-    m_layout = new QVBoxLayout(this);
-    m_layout->setContentsMargins(0, 0, 0, 0);
-    m_layout->setSpacing(4);
-    m_layout->setAlignment(Qt::AlignTop);
-
-    m_entityTitleLabel = new QLabel(this);
-    QFont titleFont = m_entityTitleLabel->font();
-    titleFont.setBold(true);
-    m_entityTitleLabel->setFont(titleFont);
-    m_layout->addWidget(m_entityTitleLabel);
-    m_entityTitleLabel->hide();
-
-    m_entityStatsPanel = new ShipStatsPanel(config, this);
-    m_layout->addWidget(m_entityStatsPanel);
-    m_entityStatsPanel->hide();
-
-    m_stationStatsLabel = new QLabel(this);
-    m_stationStatsLabel->setWordWrap(true);
-    m_layout->addWidget(m_stationStatsLabel);
-    m_stationStatsLabel->hide();
-
-    m_entitySummaryLabel = new QLabel(this);
-    m_entitySummaryLabel->setWordWrap(true);
-    m_layout->addWidget(m_entitySummaryLabel);
-    m_entitySummaryLabel->hide();
-
-    m_scrapLabel = new QLabel(this);
-    m_layout->addWidget(m_scrapLabel);
-    m_scrapLabel->hide();
-
-    hide();
-
-    registerForEvents();
-}
-
-FieldSelectionPanel::~FieldSelectionPanel()
-{
-    unregisterForEvents();
-}
-
-void FieldSelectionPanel::setSelectedEntities(const std::vector<entt::entity>& entities)
-{
-    m_selectedEntities = entities;
-    rebuild();
-}
-
-void FieldSelectionPanel::setSelectedDebris(const std::vector<entt::entity>& debris)
-{
-    m_selectedDebris = debris;
-    rebuild();
-}
-
-void FieldSelectionPanel::clearSelection()
-{
-    m_selectedEntities.clear();
-    m_selectedDebris.clear();
-    rebuild();
-}
-
-bool FieldSelectionPanel::hasSelection() const
-{
-    return !m_selectedEntities.empty() || !m_selectedDebris.empty();
-}
-
-void FieldSelectionPanel::hideAllWidgets()
-{
-    m_entityTitleLabel->hide();
-    m_entityStatsPanel->hide();
-    m_stationStatsLabel->hide();
-    m_entitySummaryLabel->hide();
-    m_scrapLabel->hide();
-}
-
-void FieldSelectionPanel::rebuild()
-{
-    if (!hasSelection())
-    {
-        // Nothing in the field category: take no space, leaving the panel to whatever
-        // the building category shows (REQ-UI-SELECTION-CATEGORIES).
-        hideAllWidgets();
-        hide();
-        return;
-    }
-
-    show();
-
-    EntityAdmin& admin = m_sim->getAdmin();
-
-    // A full single-object stats panel is shown only for a lone field object: one actor
-    // with no debris, or one piece of debris with no actors. As soon as the selection holds
-    // more than one object (multiple actors, multiple debris, or actors plus debris), the
-    // panel switches to the compact count summary (REQ-UI-FIELD-MULTI-SELECTION).
-    if (m_selectedEntities.size() == 1 && m_selectedDebris.empty())
-    {
-        m_entitySummaryLabel->hide();
-        m_scrapLabel->hide();
-        const entt::entity entity = m_selectedEntities.front();
-        if (admin.isValid(entity) && admin.hasAll<ShipIdentityComponent>(entity))
-        {
-            buildEntityShip(entity);
-        }
-        else if (admin.isValid(entity) && admin.hasAll<StationBodyComponent>(entity))
-        {
-            buildEntityStation(entity);
-        }
-        else
-        {
-            m_entityTitleLabel->hide();
-            m_entityStatsPanel->hide();
-            m_stationStatsLabel->hide();
-        }
-        return;
-    }
-
-    if (m_selectedEntities.empty() && m_selectedDebris.size() == 1)
-    {
-        // Single piece of debris: a "Debris" heading plus a "Scrap" stat row, styled like
-        // the ship/station stats panels (REQ-UI-DEBRIS-PANEL).
-        m_entitySummaryLabel->hide();
-        m_entityStatsPanel->hide();
-        m_stationStatsLabel->hide();
-        buildDebrisSingle();
-        return;
-    }
-
-    // More than one field object: a compact count summary. buildEntitySummary() appends the
-    // "Debris x N" and "Scrap x N" lines when debris is part of the selection.
-    m_entityTitleLabel->hide();
-    m_entityStatsPanel->hide();
-    m_stationStatsLabel->hide();
-    m_scrapLabel->hide();
-    buildEntitySummary();
-}
-
-void FieldSelectionPanel::refreshDisplay()
-{
-    if (!hasSelection()) { return; }
-
-    // Keep the live values current: the single-actor stats panel, the single-debris stats
-    // panel (whose Scrap row shrinks as it is collected), or the count summary (whose Scrap
-    // line shrinks likewise) — matching the layout chosen by rebuild()
-    // (REQ-UI-SHIP-STATS-PANEL, REQ-UI-DEBRIS-PANEL).
-    if (m_selectedEntities.size() == 1 && m_selectedDebris.empty())
-    {
-        refreshEntityStats();
-    }
-    else if (m_selectedEntities.empty() && m_selectedDebris.size() == 1)
-    {
-        buildDebrisSingle();
-    }
-    else
-    {
-        buildEntitySummary();
-    }
-}
-
-void FieldSelectionPanel::buildDebrisSingle()
-{
-    // "Debris" heading + a single "Scrap" stat row for the piece's remaining amount,
-    // mirroring the single-actor stats panels (REQ-UI-DEBRIS-PANEL).
-    m_entityTitleLabel->setText(tr("Debris"));
-    m_entityTitleLabel->show();
-    m_scrapLabel->setText(tr("Scrap: %1").arg(selectedDebrisScrapTotal()));
-    m_scrapLabel->show();
-}
-
-void FieldSelectionPanel::buildEntitySummary()
-{
-    EntityAdmin& admin = m_sim->getAdmin();
-
-    // Group actors by faction + kind + ship schematic, preserving first-seen order
-    // (REQ-UI-FIELD-MULTI-SELECTION).
-    std::vector<QString> keys;
-    std::map<QString, int> counts;
-    std::map<QString, QString> labels;
-
-    for (entt::entity entity : m_selectedEntities)
-    {
-        if (!admin.isValid(entity)) { continue; }
-        const bool isEnemy = admin.hasAll<FactionComponent>(entity)
-            && admin.get<FactionComponent>(entity).isEnemy;
-
-        QString key;
-        QString label;
-        if (admin.hasAll<ShipIdentityComponent>(entity))
-        {
-            const std::string& id = admin.get<ShipIdentityComponent>(entity).schematicId;
-            const QString name = QString::fromStdString(toDisplayName(id));
-            key = (isEnemy ? QStringLiteral("ship:enemy:") : QStringLiteral("ship:player:"))
-                + QString::fromStdString(id);
-            label = isEnemy ? tr("Enemy %1").arg(name) : name;
-        }
-        else if (admin.hasAll<StationBodyComponent>(entity))
-        {
-            key = isEnemy ? QStringLiteral("station:enemy") : QStringLiteral("station:player");
-            label = isEnemy ? tr("Enemy Defence Station") : tr("Player Defence Station");
-        }
-        else
-        {
-            continue;
-        }
-
-        if (counts.find(key) == counts.end())
-        {
-            keys.push_back(key);
-            labels[key] = label;
-        }
-        counts[key] += 1;
-    }
-
-    // One "<type> x <count>" line per group (matching the recipe tooltip and the building
-    // multi-selection). No total-count header, consistent with the building panel. When
-    // debris is part of the selection, a "Debris x <count>" line followed by a
-    // "Scrap x <total>" line are appended into the same label so the line spacing is
-    // uniform (REQ-UI-FIELD-MULTI-SELECTION, REQ-UI-DEBRIS-PANEL).
-    QStringList lines;
-    for (const QString& key : keys)
-    {
-        lines << tr("%1 x %2").arg(labels[key]).arg(counts[key]);
-    }
-    if (!m_selectedDebris.empty())
-    {
-        lines << tr("Debris x %1").arg(static_cast<int>(m_selectedDebris.size()));
-        lines << scrapTotalText();
-    }
-    m_entitySummaryLabel->setText(lines.join('\n'));
-    m_entitySummaryLabel->show();
-}
-
-void FieldSelectionPanel::buildEntityShip(entt::entity entity)
-{
-    EntityAdmin& admin = m_sim->getAdmin();
-    const ShipIdentityComponent& identity = admin.get<ShipIdentityComponent>(entity);
-    const HealthComponent& health = admin.get<HealthComponent>(entity);
-
-    m_entityTitleLabel->setText(tr("Ship: %1")
-        .arg(QString::fromStdString(identity.schematicId)));
-    m_entityTitleLabel->show();
-
-    const ShipStats stats = buildShipStatsFromEntity(admin, entity);
-    m_entityStatsPanel->refreshFromLive(stats, health.hp);
-    m_entityStatsPanel->setBehavior(
-        admin.get<SelectedBehaviorComponent>(entity).winner);
-    m_entityStatsPanel->setDebugDrawEnabled(m_debugDraw);
-
-    const ShipDef* schematicDef =
-        m_config->ships.findShipDef(identity.schematicId);
-    if (schematicDef)
-    {
-        const double threat = calculateShipThreatCost(
-            m_config->threatCosts, *m_config, schematicDef->id,
-            schematicDef->defaultModules);
-        m_entityStatsPanel->setThreatCost(threat);
-    }
-
-    m_entityStatsPanel->show();
-
-    m_stationStatsLabel->hide();
-}
-
-void FieldSelectionPanel::buildEntityStation(entt::entity entity)
-{
-    EntityAdmin& admin = m_sim->getAdmin();
-    const HealthComponent& health = admin.get<HealthComponent>(entity);
-
-    const bool isEnemy = admin.hasAll<FactionComponent>(entity)
-        && admin.get<FactionComponent>(entity).isEnemy;
-    m_entityTitleLabel->setText(isEnemy
-        ? tr("Enemy Defence Station")
-        : tr("Player Defence Station"));
-    m_entityTitleLabel->show();
-
-    float totalDps = 0.0f;
-    float maxRange = 0.0f;
-    bool hasWeapons = false;
-
-    admin.forEach<ModuleOwnerComponent, WeaponComponent>(
-        [&](entt::entity /*child*/, const ModuleOwnerComponent& owner, const WeaponComponent& w)
-        {
-            if (owner.owner != entity) { return; }
-            hasWeapons = true;
-            totalDps += w.damage * w.fireRateHz;
-            if (w.range_tiles > maxRange) { maxRange = w.range_tiles; }
-        });
-
-    QString statsText = tr("HP: %1 / %2")
-        .arg(static_cast<int>(health.hp + 0.5f))
-        .arg(static_cast<int>(health.maxHp + 0.5f));
-
-    if (hasWeapons)
-    {
-        statsText += tr("\nDPS: %1").arg(QString::number(static_cast<double>(totalDps), 'f', 1));
-        statsText += tr("\nRange: %1 tiles").arg(QString::number(static_cast<double>(maxRange), 'f', 1));
-    }
-
-    m_stationStatsLabel->setText(statsText);
-    m_stationStatsLabel->show();
-
-    m_entityStatsPanel->hide();
-}
-
-void FieldSelectionPanel::refreshEntityStats()
-{
-    // Only the single-actor stats panel needs a live refresh; the multi-actor summary is
-    // static counts, and GameWorldView prunes dead/despawned actors and re-emits the
-    // selection (REQ-UI-ENTITY-CLICK-SELECT), so the panel does not mutate it here.
-    if (m_selectedEntities.size() != 1) { return; }
-
-    EntityAdmin& admin = m_sim->getAdmin();
-    const entt::entity entity = m_selectedEntities.front();
-
-    if (!admin.isValid(entity) || !admin.hasAll<HealthComponent>(entity)) { return; }
-    const HealthComponent& health = admin.get<HealthComponent>(entity);
-    if (health.hp <= 0.0f) { return; }
-
-    if (admin.hasAll<ShipIdentityComponent>(entity))
-    {
-        const ShipStats stats = buildShipStatsFromEntity(admin, entity);
-        m_entityStatsPanel->refreshFromLive(stats, health.hp);
-        m_entityStatsPanel->setBehavior(
-            admin.get<SelectedBehaviorComponent>(entity).winner);
-    }
-    else if (admin.hasAll<StationBodyComponent>(entity))
-    {
-        buildEntityStation(entity);
-    }
-}
-
-int FieldSelectionPanel::selectedDebrisScrapTotal() const
-{
-    // Sum the remaining scrap across the still-living selected debris (REQ-UI-DEBRIS-PANEL).
-    int total = 0;
-    for (const DebrisInfo& info : getAllDebrisInfo(m_sim->getAdmin()))
-    {
-        if (std::find(m_selectedDebris.begin(), m_selectedDebris.end(), info.entity)
-            != m_selectedDebris.end())
-        {
-            total += info.amount;
-        }
-    }
-    return total;
-}
-
-QString FieldSelectionPanel::scrapTotalText() const
-{
-    return tr("Scrap x %1").arg(selectedDebrisScrapTotal());
-}
-
-void FieldSelectionPanel::handleEvent(std::shared_ptr<const TickAdvancedEvent> /*event*/)
-{
-    refreshDisplay();
-}
-
-void FieldSelectionPanel::handleEvent(
-    std::shared_ptr<const PlayerCommandsAppliedEvent> /*event*/)
-{
-    // Player commands are applied by a queued drain, not synchronously. When the game is
-    // paused no tick advances, so TickAdvancedEvent never fires; refresh here too.
-    refreshDisplay();
-}
-
-void FieldSelectionPanel::handleEvent(std::shared_ptr<const DebugDrawToggledEvent> event)
-{
-    m_debugDraw = event->active;
-    m_entityStatsPanel->setDebugDrawEnabled(event->active);
-}

src/ui/FieldSelectionPanel.h

@@ -1,91 +0,0 @@
-#pragma once
-
-#include <vector>
-
-#include <QString>
-#include <QWidget>
-
-#include "entt/entity/entity.hpp"
-
-#include "DebugDrawToggledEvent.h"
-#include "EventHandler.h"
-#include "PlayerCommandsAppliedEvent.h"
-#include "TickAdvancedEvent.h"
-
-struct GameConfig;
-class Simulation;
-class ShipStatsPanel;
-class QLabel;
-class QVBoxLayout;
-
-// Renders the "field" selection category — ships, defence stations and debris — as either
-// a single-object stats panel (ship, station, or debris) or a compact multi-object count
-// summary (REQ-UI-SELECTION-CATEGORIES, REQ-UI-FIELD-MULTI-SELECTION, REQ-UI-DEBRIS-PANEL).
-//
-// The panel owns its own selection state and its own widgets, and nothing else. Which of
-// the two selection categories owns the side panel is arbitrated by the parent
-// SelectedBuildingPanel: it feeds this panel through setSelectedEntities() /
-// setSelectedDebris() / clearSelection() and asks it via hasSelection(). This panel hides
-// itself whenever its selection is empty, so an inactive field category takes no space.
-class FieldSelectionPanel : public QWidget,
-                            public CombinedEventHandler<TickAdvancedEvent,
-                                                        PlayerCommandsAppliedEvent,
-                                                        DebugDrawToggledEvent>
-{
-    Q_OBJECT
-
-public:
-    FieldSelectionPanel(Simulation* sim, const GameConfig* config,
-                        QWidget* parent = nullptr);
-    ~FieldSelectionPanel() override;
-
-    // Replaces the selected actors (ships and defence stations); debris is left alone,
-    // the two coexist within the field category (REQ-UI-SELECTION-CATEGORIES).
-    void setSelectedEntities(const std::vector<entt::entity>& entities);
-    // Replaces the selected debris; the selected actors are left alone.
-    void setSelectedDebris(const std::vector<entt::entity>& debris);
-    // Drops the whole field selection — used when the building category takes over.
-    void clearSelection();
-    // True while the field category has anything selected, i.e. while this panel owns
-    // the side panel's content.
-    bool hasSelection() const;
-
-private:
-    void handleEvent(std::shared_ptr<const TickAdvancedEvent> event) override;
-    void handleEvent(std::shared_ptr<const PlayerCommandsAppliedEvent> event) override;
-    void handleEvent(std::shared_ptr<const DebugDrawToggledEvent> event) override;
-
-    // Picks the layout for the current selection and shows/hides this panel accordingly.
-    void rebuild();
-    // Keeps the live values of the layout chosen by rebuild() current.
-    void refreshDisplay();
-    void buildEntityShip(entt::entity entity);
-    void buildEntityStation(entt::entity entity);
-    void buildEntitySummary();
-    void buildDebrisSingle();
-    void refreshEntityStats();
-    void hideAllWidgets();
-    // Summed remaining scrap across the selected debris (REQ-UI-DEBRIS-PANEL).
-    int selectedDebrisScrapTotal() const;
-    // "Scrap x N" line for the multi-object summary (REQ-UI-FIELD-MULTI-SELECTION).
-    QString scrapTotalText() const;
-
-    Simulation*       m_sim;
-    const GameConfig* m_config;
-
-    bool m_debugDraw = false;
-
-    // The selected ships/defence stations. Shares the "field" selection category with
-    // debris (m_selectedDebris): both can be non-empty at once (REQ-UI-SELECTION-CATEGORIES).
-    std::vector<entt::entity> m_selectedEntities;
-    std::vector<entt::entity> m_selectedDebris;
-
-    QVBoxLayout*    m_layout;
-    QLabel*         m_entityTitleLabel;
-    ShipStatsPanel* m_entityStatsPanel;
-    QLabel*         m_stationStatsLabel;
-    QLabel*         m_entitySummaryLabel;
-    // Shows the debris "Scrap" stat row (single selection) — the scrap total for the
-    // multi-object summary lives in m_entitySummaryLabel instead.
-    QLabel*         m_scrapLabel;
-};

src/ui/FloatingPanel.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <vector>
+
+#include <QRect>
+
+// A widget floating over the game world view (REQ-UI-WORLD-SIZE). MainWindow places all
+// of them in one ordered pass -- build button bar, then controls panel, then selection
+// panel -- and each places itself into the space the earlier ones have not taken. The
+// order is the priority the requirements state: the bar never moves for anyone
+// (REQ-UI-BUILD-BAR), the controls panel steps around the bar (REQ-UI-CONTROLS-PANEL),
+// and keeping clear of both is the selection panel's job (REQ-UI-SELECTION-PANEL).
+//
+// A widget never re-places itself, because what it may take depends on the widgets placed
+// before it. It instead publishes FloatingLayoutInvalidatedEvent whenever its content or
+// its visibility changed, and the owner re-runs the whole pass.
+class FloatingPanel
+{
+public:
+    virtual ~FloatingPanel() = default;
+
+    // Sets this widget's own geometry within viewRect, keeping clear of occupiedRects --
+    // the geometry of every floating widget already placed in this pass, in the same
+    // coordinates. A widget with nothing to show hides itself and takes no space.
+    virtual void placeIn(const QRect& viewRect,
+                         const std::vector<QRect>& occupiedRects) = 0;
+};

src/ui/GameWorldView.cpp

@@ -1,6 +1,7 @@
 #include "GameWorldView.h"
 #include "PlacementRules.h"
 #include "FactoryQueries.h"
+#include "BlueprintLibrary.h"
 
 #include <algorithm>
 #include <cctype>
@@ -46,6 +47,8 @@
 #include "ItemIconCache.h"
 #include "PositionComponent.h"
 #include "DebrisSystem.h"
+#include "SelectionAnchorChangedEvent.h"
+#include "SelectionBounds.h"
 #include "SelectionChangedEvent.h"
 #include "ShipIdentityComponent.h"
 #include "ShipSystem.h"
@@ -73,6 +76,23 @@
 namespace
 {
 
+// The action a left-button gesture triggers, with the Ctrl variant falling back to the
+// plain one wherever nothing is bound to it. That fallback is what keeps Ctrl+click
+// placing a building in builder mode and Ctrl+drag deconstructing an area: the modifier
+// only means something where an action claims it (REQ-UI-CONTROLS-CONTENT).
+ControlAction resolveLeftGesture(bool controlHeld, bool isDrag,
+                                 const ControlContext& context)
+{
+    if (controlHeld)
+    {
+        const ControlAction action = resolveMouseAction(
+            isDrag ? MouseBinding::CtrlLeftDrag : MouseBinding::CtrlLeftClick, context);
+        if (action != ControlAction::None) { return action; }
+    }
+    return resolveMouseAction(isDrag ? MouseBinding::LeftDrag : MouseBinding::LeftClick,
+                              context);
+}
+
 // Keep only the filter entries whose item type is currently unlocked
 // (REQ-LOCK-UI-BLUEPRINT). An empty result means "accept all".
 std::vector<ItemType> filterUnlockedItems(const std::vector<ItemType>& filter,
@@ -128,6 +148,7 @@ GameWorldView::GameWorldView(Simulation* sim, const GameConfig* config,
     , m_debugDraw(false)
     , m_rng(std::random_device{}())
     , m_boxSelecting(false)
+    , m_boxDragMoved(false)
     , m_gameOverShown(false)
     , m_schematicChoiceShown(false)
 {
@@ -274,12 +295,12 @@ void GameWorldView::onFrame()
         const bool viewMoved =
             m_camera.advance(m_panDirection, elapsed, getScrollBounds());
 
-        // While the view scrolls, the tile under a stationary cursor changes,
-        // so refresh the box-select rectangle even though no mouse move fires.
-        if (m_boxSelecting && viewMoved)
+        // Two things no mouse move reports: the world position under a stationary
+        // cursor changing as the view scrolls, and the cursor crossing onto a panel
+        // or out of the window, which ends the hover (REQ-BLD-GHOST).
+        if (viewMoved || isHoverLive() != m_hoverLive)
         {
-            m_boxCurrentTile =
-                getCoordinates().widgetToTile(mapFromGlobal(QCursor::pos()));
+            refreshHover();
         }
     }
 
@@ -400,8 +421,14 @@ void GameWorldView::paintGL()
 
 WorldRenderFrame GameWorldView::makeRenderFrame() const
 {
-    return WorldRenderFrame{m_selection, m_buildMode, m_activeBeams, m_boxSelecting,
-                            m_boxStartTile, m_boxCurrentTile, m_debugDraw};
+    // A box only reaches the renderer once the gesture reads as a drag: below the
+    // threshold there is nothing to draw and nothing the box marks that hovering does
+    // not mark already (REQ-UI-MULTI-SELECT).
+    std::optional<QRectF> boxWorldRect;
+    if (m_boxSelecting && m_boxDragMoved) { boxWorldRect = getBoxWorldRect(); }
+
+    return WorldRenderFrame{m_selection, m_buildMode, m_activeBeams, boxWorldRect,
+                            m_debugDraw};
 }
 
 // ---------------------------------------------------------------------------
@@ -678,7 +705,7 @@ void GameWorldView::transferConfigTo(BuildingId id, const BlueprintBuilding& sou
     if (source.type == BuildingType::Splitter)
     {
         // Operational splitters are configured by tile, sites by BuildingId (mirrors
-        // SelectedBuildingPanel::onSplitterFilterChanged). Locked item types are dropped
+        // SelectionPanel::onSplitterFilterChanged). Locked item types are dropped
         // per REQ-LOCK-UI-BLUEPRINT.
         const std::vector<ItemType> filterA = filterUnlockedItems(source.splitterFilterA, *m_sim);
         const std::vector<ItemType> filterB = filterUnlockedItems(source.splitterFilterB, *m_sim);
@@ -723,8 +750,10 @@ void GameWorldView::transferConfigTo(BuildingId id, const BlueprintBuilding& sou
 void GameWorldView::updateTunnelGhost()
 {
     // The connection preview and entry/exit switch only apply at a valid placement
-    // (REQ-BLD-TUNNEL-MODE); at an invalid position the ghost stays a plain entry.
-    if (!m_buildMode.isGhostValid())
+    // (REQ-BLD-TUNNEL-MODE); at an invalid position, and where the cursor points at
+    // no tile at all, the ghost stays a plain entry.
+    const std::optional<QPoint>& ghostTile = m_buildMode.getGhostTile();
+    if (!ghostTile.has_value() || !m_buildMode.isGhostValid())
     {
         m_buildMode.setTunnelGhost(BuildingType::TunnelEntry, std::nullopt);
         return;
@@ -734,7 +763,7 @@ void GameWorldView::updateTunnelGhost()
     const TunnelLookup  lookup  = makeTunnelLookup(tunnels);
 
     const TunnelCompletion completion =
-        resolveTunnelCompletion(lookup, m_buildMode.getGhostTile(),
+        resolveTunnelCompletion(lookup, *ghostTile,
                                 m_buildMode.getGhostRotation(),
                                 m_config->world.tunnelMaxDistance_tiles, m_cursorWorldPos);
     m_buildMode.setTunnelGhost(completion.resolvedType, completion.partnerTile);
@@ -1075,7 +1104,7 @@ void GameWorldView::keyPressEvent(QKeyEvent* event)
     // Keys are turned into actions and published by the input mapper
     // (REQ-UI-HOTKEYS); this widget reacts to those as an ordinary subscriber, so
     // nothing is handled here directly.
-    if (m_inputMapper.handleKeyPress(event)) { return; }
+    if (m_inputMapper.handleKeyPress(event, getControlContext())) { return; }
 
     QOpenGLWidget::keyPressEvent(event);
 }
@@ -1087,7 +1116,7 @@ void GameWorldView::keyReleaseEvent(QKeyEvent* event)
         QOpenGLWidget::keyReleaseEvent(event);
         return;
     }
-    if (m_inputMapper.handleKeyRelease(event)) { return; }
+    if (m_inputMapper.handleKeyRelease(event, getControlContext())) { return; }
     QOpenGLWidget::keyReleaseEvent(event);
 }
 
@@ -1101,36 +1130,98 @@ void GameWorldView::focusOutEvent(QFocusEvent* event)
     QOpenGLWidget::focusOutEvent(event);
 }
 
+void GameWorldView::setBlueprintLibrary(const BlueprintLibrary* library)
+{
+    m_blueprintLibrary = library;
+}
+
+ControlContext GameWorldView::getControlContext() const
+{
+    ControlContext context;
+    context.mode                   = m_buildMode.getMode();
+    context.draggingBelt           = m_buildMode.isDraggingBelt();
+    context.hoveredGhostIsTransfer = m_buildMode.isHoveredGhostTransfer();
+    // The type a click would actually place, so the panel agrees with the ghost when
+    // tunnel mode resolves to an exit (REQ-BLD-TUNNEL-MODE).
+    if (m_buildMode.isBuilderMode())
+    {
+        context.builderType = m_buildMode.getEffectiveBuilderType();
+    }
+
+    // Buildings win over field objects, so the two are never both non-empty
+    // (REQ-UI-SELECTION-CATEGORIES).
+    const std::vector<BuildingId>&   buildings = m_selection.getSelectedBuildings();
+    const std::vector<entt::entity>& actors    = m_selection.getSelectedActors();
+    const std::vector<entt::entity>& debris    = m_selection.getSelectedDebris();
+    if (!buildings.empty())
+    {
+        context.selection      = ControlSelection::Buildings;
+        context.selectionCount = static_cast<int>(buildings.size());
+    }
+    else if (!actors.empty() || !debris.empty())
+    {
+        context.selection      = ControlSelection::FieldObjects;
+        context.selectionCount = static_cast<int>(actors.size() + debris.size());
+    }
+
+    if (m_blueprintLibrary)
+    {
+        context.placeableBuildingSelected = m_blueprintLibrary->getCanCaptureSelection();
+        context.temporaryBlueprintExists  = m_blueprintLibrary->getHasTemporaryBlueprint();
+    }
+    return context;
+}
+
+QString GameWorldView::getActiveBlueprintName() const
+{
+    if (!m_buildMode.isBlueprintMode()) { return QString(); }
+    return m_buildMode.getBlueprint().name;
+}
+
 void GameWorldView::mousePressEvent(QMouseEvent* event)
 {
     const WorldCoordinates coordinates = getCoordinates();
+    const ControlContext   context     = getControlContext();
 
     if (event->button() != Qt::LeftButton)
     {
         if (event->button() == Qt::RightButton)
         {
-            if (m_buildMode.isBuilderMode() && m_buildMode.isDraggingBelt())
+            switch (resolveMouseAction(MouseBinding::RightClick, context))
             {
-                // Cancel the in-progress belt drag without placing anything;
-                // stay in belt builder mode (REQ-BLD-BELT-DRAG).
+            case ControlAction::CancelBeltLine:
+                // Drop the in-progress path without placing anything; belt builder
+                // mode stays active (REQ-BLD-BELT-DRAG).
                 m_buildMode.cancelBeltDrag();
-            }
-            else if (m_buildMode.getMode() != BuildMode::None)
-            {
+                break;
+            case ControlAction::ExitMode:
                 m_buildMode.exitCurrentMode();
+                break;
+            default:
+                break;
             }
         }
         return;
     }
 
     const QPoint tile = coordinates.widgetToTile(event->pos());
+    const bool   controlHeld = (event->modifiers() & Qt::ControlModifier) != 0;
 
-    if (m_buildMode.isBuilderMode())
+    // A press begins the click gesture; whether it turns out to be a drag is settled on
+    // release, where the drag binding is resolved instead.
+    switch (resolveLeftGesture(controlHeld, /*isDrag*/ false, context))
     {
-        if (m_buildMode.getBuilderType() == BuildingType::Belt)
+    case ControlAction::Place:
+    case ControlAction::ApplySettings:
+        if (m_buildMode.isBlueprintMode())
         {
-            // Deferred placement: start the drag and show the path ghost; nothing
-            // is placed until release (REQ-BLD-BELT-DRAG).
+            placeBlueprintAtTile(tile);
+        }
+        else if (m_buildMode.getBuilderType() == BuildingType::Belt)
+        {
+            // Belts place by dragging, so the press only anchors the path and shows its
+            // ghost; nothing is placed until release, and a plain click is the one-tile
+            // case (REQ-BLD-BELT-DRAG).
             m_buildMode.beginBeltDrag(tile);
             m_cursorWorldPos = coordinates.widgetToWorld(event->pos());
             recomputeBeltDragPath(tile);
@@ -1139,34 +1230,35 @@ void GameWorldView::mousePressEvent(QMouseEvent* event)
         {
             placeAtTile(tile);
         }
-    }
-    else if (m_buildMode.isBlueprintMode())
-    {
-        placeBlueprintAtTile(tile);
-    }
-    else if (m_buildMode.isDeconstructMode())
-    {
+        break;
+
+    case ControlAction::ToggleDeconstruct:
         // Start a deconstruct box drag; a plain click resolves as a 1x1 box on
         // release (REQ-BLD-DECONSTRUCT-CLICK, REQ-BLD-DECONSTRUCT-BOX).
-        m_boxSelecting   = true;
-        m_boxStartTile   = tile;
-        m_boxCurrentTile = tile;
-    }
-    else
-    {
-        const bool ctrl = (event->modifiers() & Qt::ControlModifier) != 0;
+        m_boxSelecting    = true;
+        m_boxStartWorld   = coordinates.widgetToWorld(event->pos());
+        m_boxCurrentWorld = m_boxStartWorld;
+        m_boxDragMoved    = false;
+        break;
 
+    case ControlAction::Select:
+    case ControlAction::AddToSelection:
         // Only a click that hit nothing starts a box drag. Starting one on a hit
         // would re-resolve the same object as a 1x1 box on release and undo the
         // click: a Ctrl+click would toggle the building off, then straight back on.
-        if (!selectAtPoint(tile, coordinates.widgetToWorld(event->pos()), ctrl))
+        if (!selectAtPoint(tile, coordinates.widgetToWorld(event->pos()), controlHeld))
         {
             // selectAtPoint has already cleared the selection unless Ctrl is
             // preserving it for an additive drag.
             m_boxSelecting    = true;
-            m_boxStartTile    = tile;
-            m_boxCurrentTile  = tile;
+            m_boxStartWorld   = coordinates.widgetToWorld(event->pos());
+            m_boxCurrentWorld = m_boxStartWorld;
+            m_boxDragMoved    = false;
         }
+        break;
+
+    default:
+        break;
     }
 }
 
@@ -1181,6 +1273,7 @@ bool GameWorldView::selectAtPoint(QPoint tile, QVector2D worldPos, bool additive
     if (!buildingHit.has_value()) { buildingHit = siteAtTile(tile); }
     if (buildingHit.has_value())
     {
+        publishSelectionAnchor(mode, {*buildingHit}, {}, {});
         m_selection.selectBuildings({*buildingHit}, mode);
         return true;
     }
@@ -1188,6 +1281,7 @@ bool GameWorldView::selectAtPoint(QPoint tile, QVector2D worldPos, bool additive
     const entt::entity actorHit = entityAtWorldPos(m_sim->getAdmin(), worldPos);
     if (actorHit != entt::null)
     {
+        publishSelectionAnchor(mode, {}, {actorHit}, {});
         m_selection.selectFieldObjects({actorHit}, {}, mode);
         return true;
     }
@@ -1195,6 +1289,7 @@ bool GameWorldView::selectAtPoint(QPoint tile, QVector2D worldPos, bool additive
     const entt::entity debrisHit = debrisAtWorldPos(m_sim->getAdmin(), worldPos);
     if (debrisHit != entt::null)
     {
+        publishSelectionAnchor(mode, {}, {}, {debrisHit});
         m_selection.selectFieldObjects({}, {debrisHit}, mode);
         return true;
     }
@@ -1211,20 +1306,22 @@ void GameWorldView::selectInBox(bool additive)
     // mode: a Ctrl box adds and never deselects, where a Ctrl click toggles.
     const SelectionMode mode = additive ? SelectionMode::Add : SelectionMode::Replace;
 
+    const QRectF worldBox = getBoxWorldRect();
+
     const std::vector<BuildingId> boxIds =
-        buildingsInBox(m_sim->getFactoryState(), m_boxStartTile, m_boxCurrentTile);
+        buildingsInBox(m_sim->getFactoryState(), worldBox);
     if (!boxIds.empty())
     {
+        publishSelectionAnchor(mode, boxIds, {}, {});
         m_selection.selectBuildings(boxIds, mode);
         return;
     }
 
-    const std::vector<entt::entity> boxActors =
-        actorsInBox(m_sim->getAdmin(), m_boxStartTile, m_boxCurrentTile);
-    const std::vector<entt::entity> boxDebris =
-        debrisInBox(m_sim->getAdmin(), m_boxStartTile, m_boxCurrentTile);
+    const std::vector<entt::entity> boxActors = actorsInBox(m_sim->getAdmin(), worldBox);
+    const std::vector<entt::entity> boxDebris = debrisInBox(m_sim->getAdmin(), worldBox);
     if (!boxActors.empty() || !boxDebris.empty())
     {
+        publishSelectionAnchor(mode, {}, boxActors, boxDebris);
         m_selection.selectFieldObjects(boxActors, boxDebris, mode);
         return;
     }
@@ -1233,11 +1330,43 @@ void GameWorldView::selectInBox(bool additive)
     if (!additive) { m_selection.clearAll(); }
 }
 
-void GameWorldView::mouseMoveEvent(QMouseEvent* event)
+void GameWorldView::clearSelectionForBuildMode()
 {
+    m_selection.clearAll();
+}
+
+bool GameWorldView::isHoverLive() const
+{
+    // underMouse() is false while the cursor sits on one of the floating panels,
+    // which are siblings of this widget rather than children, and while it is
+    // outside the window. A drag holding the button is the exception: it tracks the
+    // cursor wherever it goes until the button comes back up (REQ-UI-MULTI-SELECT,
+    // REQ-BLD-BELT-DRAG).
+    return underMouse() || m_boxSelecting || m_buildMode.isDraggingBelt();
+}
+
+void GameWorldView::refreshHover()
+{
+    if (isHoverLive())
+    {
+        updateHoverAt(mapFromGlobal(QCursor::pos()));
+    }
+    else
+    {
+        m_buildMode.clearHover();
+        m_hoverLive = false;
+    }
+}
+
+void GameWorldView::updateHoverAt(QPoint cursorWidgetPos)
+{
+    // Reached either from a mouse move, which only this widget receives, or from a
+    // hover refresh that has already established the cursor is on the world.
+    m_hoverLive = true;
+
     const WorldCoordinates coordinates = getCoordinates();
-    const QPoint tile = coordinates.widgetToTile(event->pos());
-    m_cursorWorldPos  = coordinates.widgetToWorld(event->pos());
+    const QPoint tile = coordinates.widgetToTile(cursorWidgetPos);
+    m_cursorWorldPos  = coordinates.widgetToWorld(cursorWidgetPos);
 
     if (m_buildMode.isBuilderMode())
     {
@@ -1263,18 +1392,101 @@ void GameWorldView::mouseMoveEvent(QMouseEvent* event)
     else if (m_buildMode.isBlueprintMode())
     {
         m_buildMode.setBlueprintGhostTile(tile);
+
+        // Resolved here, once, through the same classifier the click and the ghost's
+        // colour use, and stored on the mode: the controls panel says "Apply settings"
+        // exactly when clicking would transfer (REQ-UI-BLUEPRINT-TRANSFER). Only a
+        // single-building blueprint hit-tests the cursor, so only it can be a hovered
+        // transfer target.
+        const std::vector<BlueprintBuilding>& buildings =
+            m_buildMode.getBlueprint().buildings;
+        bool transfer = false;
+        if (buildings.size() == 1)
+        {
+            transfer = resolveBlueprintGhostHere(buildings.front(), tile).action
+                       == BlueprintGhostAction::Transfer;
+        }
+        m_buildMode.setHoveredGhostTransfer(transfer);
     }
     else if (m_buildMode.isDeconstructMode())
     {
         m_buildMode.setDeconstructHoverBuildingId(buildingAtTile(tile));
-        if (m_boxSelecting) { m_boxCurrentTile = tile; }
+        if (m_boxSelecting) { updateBoxDrag(cursorWidgetPos); }
     }
     else if (m_boxSelecting)
     {
-        m_boxCurrentTile = tile;
+        updateBoxDrag(cursorWidgetPos);
     }
 }
 
+void GameWorldView::updateBoxDrag(QPoint cursorWidgetPos)
+{
+    const WorldCoordinates coordinates = getCoordinates();
+    m_boxCurrentWorld = coordinates.widgetToWorld(cursorWidgetPos);
+
+    // Measured against where the anchor sits on screen right now, not against where
+    // the button went down: a view that scrolls under a held button moves the anchor
+    // away from a motionless cursor, and that is a drag as much as moving the mouse
+    // is (REQ-UI-MULTI-SELECT).
+    const QPointF anchorWidgetPos = coordinates.worldToWidget(m_boxStartWorld);
+    const qreal   travel_px = std::abs(cursorWidgetPos.x() - anchorWidgetPos.x())
+                            + std::abs(cursorWidgetPos.y() - anchorWidgetPos.y());
+    if (travel_px >= kBoxDragThresholdPixels) { m_boxDragMoved = true; }
+}
+
+QRectF GameWorldView::getBoxWorldRect() const
+{
+    if (!m_boxDragMoved)
+    {
+        // Still a click: the rectangle it spans has no area and would cover nothing,
+        // so the box is the whole tile the button went down on instead — what the
+        // click points at (REQ-UI-MULTI-SELECT, REQ-BLD-DECONSTRUCT-CLICK).
+        return QRectF(std::floor(m_boxStartWorld.x()), std::floor(m_boxStartWorld.y()),
+                      1.0, 1.0);
+    }
+    return QRectF(QPointF(m_boxStartWorld.x(), m_boxStartWorld.y()),
+                  QPointF(m_boxCurrentWorld.x(), m_boxCurrentWorld.y())).normalized();
+}
+
+void GameWorldView::publishSelectionAnchor(SelectionMode mode,
+                                           const std::vector<BuildingId>& buildings,
+                                           const std::vector<entt::entity>& actors,
+                                           const std::vector<entt::entity>& debris)
+{
+    // An additive gesture onto something already selected is growing that selection, not
+    // starting one, and the panel stays where it was put (REQ-UI-SELECTION-PANEL).
+    const bool startsSelection =
+        (mode == SelectionMode::Replace) || (m_selection.getSelectedBuildings().empty()
+                                             && m_selection.getSelectedActors().empty()
+                                             && m_selection.getSelectedDebris().empty());
+    if (!startsSelection)
+    {
+        return;
+    }
+
+    // Screen space, frozen here: the panel is placed against where the selection is at
+    // this moment and stays there, however far the view scrolls or the objects move
+    // afterwards.
+    const QRect anchorRect = getSelectionWidgetRect(*m_sim, getCoordinates(),
+                                                    buildings, actors, debris);
+    if (anchorRect.isNull())
+    {
+        return;
+    }
+    // The gap the panel keeps from that rectangle is half a tile (REQ-UI-SELECTION-PANEL),
+    // and this is where the tile size is known. It is sampled in the same moment as the
+    // rectangle and travels with it, so both describe the view as it stood when the
+    // selection started.
+    const int selectionGapPx = qRound(getCoordinates().getTilePx() / 2.0f);
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<SelectionAnchorChangedEvent>(anchorRect, selectionGapPx));
+}
+
+void GameWorldView::mouseMoveEvent(QMouseEvent* event)
+{
+    updateHoverAt(event->pos());
+}
+
 void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
 {
     if (event->button() != Qt::LeftButton) { return; }
@@ -1292,9 +1504,13 @@ void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
         m_boxSelecting = false;
 
         const std::vector<BuildingId> boxIds =
-            buildingsInBox(m_sim->getFactoryState(), m_boxStartTile, m_boxCurrentTile);
+            buildingsInBox(m_sim->getFactoryState(), getBoxWorldRect());
 
-        if (m_buildMode.isDeconstructMode())
+        const bool controlHeld = (event->modifiers() & Qt::ControlModifier) != 0;
+        const ControlAction dragAction =
+            resolveLeftGesture(controlHeld, /*isDrag*/ true, getControlContext());
+
+        if (dragAction == ControlAction::DeconstructArea)
         {
             const FactoryState& factory = m_sim->getFactoryState();
 
@@ -1356,7 +1572,9 @@ void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
             return;
         }
 
-        selectInBox((event->modifiers() & Qt::ControlModifier) != 0);
+        // A Ctrl box adds and never deselects, where a plain one replaces
+        // (REQ-UI-MULTI-SELECT).
+        selectInBox(dragAction == ControlAction::AddAreaToSelection);
     }
 }
 
@@ -1369,8 +1587,14 @@ void GameWorldView::rotateGhost(bool clockwise)
     if (m_buildMode.isBuilderMode())
     {
         m_buildMode.rotateGhost(clockwise);
+
+        // The new facing is kept whatever the cursor is over; what it means for the
+        // world is only re-resolved while the cursor points at a tile (REQ-BLD-GHOST).
+        const std::optional<QPoint>& ghostTile = m_buildMode.getGhostTile();
+        if (!ghostTile.has_value()) { return; }
+
         m_buildMode.setGhostValidity(
-            canPlaceBuildingHere(m_buildMode.getBuilderType(), m_buildMode.getGhostTile(),
+            canPlaceBuildingHere(m_buildMode.getBuilderType(), *ghostTile,
                              m_buildMode.getGhostRotation()));
         // A new facing changes which tunnels the ghost could complete (REQ-BLD-TUNNEL-MODE).
         if (m_buildMode.isTunnelMode()) { updateTunnelGhost(); }
@@ -1378,7 +1602,7 @@ void GameWorldView::rotateGhost(bool clockwise)
         // without waiting for the next mouse move (REQ-BLD-BELT-DRAG).
         if (m_buildMode.isDraggingBelt())
         {
-            recomputeBeltDragPath(m_buildMode.getGhostTile());
+            recomputeBeltDragPath(*ghostTile);
         }
     }
     else if (m_buildMode.isBlueprintMode())
@@ -1507,7 +1731,12 @@ void GameWorldView::handleEvent(std::shared_ptr<const BeamFiredEvent> event)
 
 void GameWorldView::handleEvent(std::shared_ptr<const BuildingTypeSelectedEvent> event)
 {
+    clearSelectionForBuildMode();
     m_buildMode.enterBuilderMode(event->type);
+    // A mode entered by hotkey usually leaves the cursor exactly where it was, and no
+    // mouse move follows to place the ghost; entered from a build button it leaves the
+    // cursor on the bar, where there is nothing to hover (REQ-BLD-GHOST).
+    refreshHover();
 }
 
 void GameWorldView::handleEvent(std::shared_ptr<const ExitBuilderModeRequestedEvent> /*event*/)
@@ -1517,12 +1746,18 @@ void GameWorldView::handleEvent(std::shared_ptr<const ExitBuilderModeRequestedEv
 
 void GameWorldView::handleEvent(std::shared_ptr<const DeconstructModeToggleRequestedEvent> /*event*/)
 {
+    clearSelectionForBuildMode();
     m_buildMode.toggleDeconstructMode();
+    refreshHover();
 }
 
 void GameWorldView::handleEvent(std::shared_ptr<const BlueprintPlacementRequestedEvent> event)
 {
+    // The blueprint arrives already built from the selection this drops
+    // (REQ-UI-BLUEPRINT-TEMP, REQ-UI-SELECTION-EXCLUSIVE).
+    clearSelectionForBuildMode();
     m_buildMode.enterBlueprintMode(event->blueprint);
+    refreshHover();
 }
 
 void GameWorldView::handleEvent(std::shared_ptr<const ExitBlueprintModeRequestedEvent> /*event*/)
@@ -1565,14 +1800,19 @@ void GameWorldView::handleEvent(std::shared_ptr<const GhostRotationRequestedEven
 
 void GameWorldView::handleEvent(std::shared_ptr<const ModeCancelRequestedEvent> /*event*/)
 {
-    // One key backs out of whichever mode is active, and enters deconstruct mode
-    // when none is (REQ-UI-HOTKEYS).
-    // One key backs out of whichever mode is active, and enters deconstruct mode
-    // when none is (REQ-UI-HOTKEYS).
+    // One key backs out of whichever mode is active, and enters deconstruct mode when
+    // none is (REQ-UI-HOTKEYS). The selection case of that key never reaches here: it
+    // resolves to its own event, so there is nothing left to clear by the time the
+    // fallthrough enters deconstruct mode (REQ-UI-SELECTION-EXCLUSIVE).
     if (m_buildMode.getMode() == BuildMode::None) { m_buildMode.toggleDeconstructMode(); }
     else                                          { m_buildMode.exitCurrentMode(); }
 }
 
+void GameWorldView::handleEvent(std::shared_ptr<const SelectionClearRequestedEvent> /*event*/)
+{
+    m_selection.clearAll();
+}
+
 void GameWorldView::handleEvent(std::shared_ptr<const DebugDrawToggleRequestedEvent> /*event*/)
 {
     m_debugDraw = !m_debugDraw;
@@ -1582,7 +1822,7 @@ void GameWorldView::handleEvent(std::shared_ptr<const DebugDrawToggleRequestedEv
 
 void GameWorldView::handleEvent(std::shared_ptr<const CommandRequestedEvent> event)
 {
-    // Other widgets (MainWindow, SelectedBuildingPanel) request commands via this
+    // Other widgets (MainWindow, SelectionPanel) request commands via this
     // event; GameWorldView owns the CommandManager and enqueues them.
     if (event->command && event->command->kind == CommandKind::Reset)
     {

src/ui/GameWorldView.h

@@ -37,6 +37,7 @@
 #include "ModeCancelRequestedEvent.h"
 #include "PanDirectionChangedEvent.h"
 #include "PauseToggleRequestedEvent.h"
+#include "SelectionClearRequestedEvent.h"
 #include "SpeedStepRequestedEvent.h"
 #include "DebugDrawToggledEvent.h"
 #include "ArtifactCountChangedEvent.h"
@@ -64,6 +65,7 @@
 
 struct Command;
 struct ParsedReplay;
+class BlueprintLibrary;
 class ItemIconCache;
 class ReplayPlayer;
 class Simulation;
@@ -82,6 +84,7 @@ class GameWorldView : public QOpenGLWidget,
                                                   SpeedStepRequestedEvent,
                                                   GhostRotationRequestedEvent,
                                                   ModeCancelRequestedEvent,
+                                                  SelectionClearRequestedEvent,
                                                   DebugDrawToggleRequestedEvent,
                                                   CommandRequestedEvent>
 {
@@ -102,6 +105,21 @@ public:
     void setGameSpeed(double multiplier);
     void resetForNewGame();
 
+    // The blueprint library is constructed after this widget, so it arrives by setter.
+    // Not owned; supplies the two facts about blueprints that the control context needs
+    // (REQ-UI-CONTROLS-CONTENT).
+    void setBlueprintLibrary(const BlueprintLibrary* library);
+
+    // The player's current situation, as the one snapshot every reader of the control
+    // table works from: this widget's own mouse dispatch, the input mapper, and the
+    // controls panel (REQ-UI-CONTROLS-CONTENT). Built here because this widget owns the
+    // build mode and the selection.
+    ControlContext getControlContext() const;
+
+    // Name of the blueprint being placed, for the controls panel's heading. Empty while
+    // no blueprint is active and for the unnamed temporary one (REQ-UI-BLUEPRINT-TEMP).
+    QString getActiveBlueprintName() const;
+
 protected:
     void initializeGL() override;
     void paintGL() override;
@@ -133,6 +151,7 @@ private:
     void handleEvent(std::shared_ptr<const SpeedStepRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const GhostRotationRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const ModeCancelRequestedEvent> event) override;
+    void handleEvent(std::shared_ptr<const SelectionClearRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const DebugDrawToggleRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const CommandRequestedEvent> event) override;
 
@@ -210,6 +229,47 @@ private:
     // which is the only case that goes on to start a box drag.
     bool                     selectAtPoint(QPoint tile, QVector2D worldPos, bool additive);
     void                     selectInBox(bool additive);
+    // A build mode and a selection are mutually exclusive, so entering any mode drops
+    // the selection (REQ-UI-SELECTION-EXCLUSIVE). Called from each of the three events
+    // that enter a mode -- the only ways in, whichever button or key the player used.
+    // Clearing an empty selection publishes nothing, so the exiting half of the
+    // deconstruct toggle costs nothing.
+    void                     clearSelectionForBuildMode();
+    // Whether the cursor points at the game world at all: it does while it is over
+    // this widget, and while a belt or box drag holds the button, which goes on
+    // following the cursor onto the floating panels and past the window edge.
+    bool                     isHoverLive() const;
+    // Re-derives the hover from wherever the cursor is now, or drops it when the
+    // cursor points at nothing (REQ-BLD-GHOST). The entry point for everything a
+    // mouse move does not cover: a scrolling view, a cursor crossing onto a panel or
+    // out of the window, and a mode just entered under a cursor that has not moved.
+    void                     refreshHover();
+    // Re-resolves everything that follows from where the cursor points into the world:
+    // the ghost tile and its validity, the tunnel ends, a running belt or box drag, the
+    // deconstruct hover. Called for every mouse move, and once per frame while the view
+    // scrolls under a cursor that has not moved, since that changes the world position
+    // the cursor points at just as moving the mouse does (REQ-BLD-GHOST).
+    void                     updateHoverAt(QPoint cursorWidgetPos);
+    // Moves the running box drag's far corner to the world position under
+    // `cursorWidgetPos` and, once the cursor sits far enough from where the anchor is
+    // drawn, promotes the gesture from a click to a drag. Every corner update goes
+    // through here, including the ones a scrolling view causes under a cursor that
+    // has not moved (REQ-UI-MULTI-SELECT).
+    void                     updateBoxDrag(QPoint cursorWidgetPos);
+    // The box the drag currently spans, in world coordinates and normalized: the
+    // rectangle between its two corners once it reads as a drag, and the whole tile
+    // the button went down on before that (REQ-UI-MULTI-SELECT). Both what is drawn
+    // and what is selected come from here, so they can never disagree.
+    QRectF                   getBoxWorldRect() const;
+    // Publishes where on the screen the selection about to be made sits, so the
+    // selection panel can be placed beside it (REQ-UI-SELECTION-PANEL). Called with
+    // what is about to be selected, immediately before selecting it, and publishes
+    // nothing unless that selection is starting rather than growing.
+    void                     publishSelectionAnchor(
+                                 SelectionMode mode,
+                                 const std::vector<BuildingId>& buildings,
+                                 const std::vector<entt::entity>& actors,
+                                 const std::vector<entt::entity>& debris);
     void                     stepSpeed(int delta);
     void                     placeAtTile(QPoint tile);
 
@@ -235,6 +295,11 @@ private:
     // paused or slowed, instead of fading on wall-clock time (REQ-SHP-FIRING-BEAM).
     static constexpr Tick    kBeamLifetimeTicks      = secondsToTicks(0.3);
 
+    // How far the cursor must travel from the press position, in widget pixels
+    // (Manhattan distance), before a box drag shows its rectangle
+    // (REQ-UI-MULTI-SELECT).
+    static constexpr int     kBoxDragThresholdPixels = 2;
+
     Simulation*          m_sim;
     const GameConfig*    m_config;
     const VisualsConfig* m_visuals;
@@ -273,6 +338,11 @@ private:
     // end tile closest to the cursor when snapping to a building (REQ-BLD-BELT-DRAG)
     // and to resolve the tunnel ghost sub-tile (REQ-BLD-TUNNEL-MODE).
     QVector2D                            m_cursorWorldPos;
+    // Whether the hover state currently stands for a cursor pointing at the world,
+    // so that losing it is noticed once rather than every frame. Kept here rather
+    // than asked of Qt per reader: it has to agree with what was last written to the
+    // build mode controller, not with where the cursor happens to be mid-frame.
+    bool                                 m_hoverLive = false;
 
     bool     m_debugDraw;
 
@@ -280,9 +350,20 @@ private:
     // between them (REQ-UI-SELECTION-CATEGORIES), including publishing the change
     // events. This widget only resolves what was hit.
     SelectionController   m_selection;
+    // Not owned; set after construction, so null until MainWindow has built it.
+    const BlueprintLibrary* m_blueprintLibrary = nullptr;
     bool                  m_boxSelecting;
-    QPoint                m_boxStartTile;
-    QPoint                m_boxCurrentTile;
+    // The drag's two corners in world coordinates, unsnapped: where the button went
+    // down and where the cursor is now (REQ-UI-MULTI-SELECT). World rather than
+    // widget coordinates so the anchor keeps the spot in the world it was placed on
+    // when the view scrolls under a held button.
+    QVector2D             m_boxStartWorld;
+    QVector2D             m_boxCurrentWorld;
+    // Whether the cursor has moved far enough from the anchor for this to read as a
+    // drag. Until it has, the rectangle is not drawn and the box resolves as the
+    // whole anchor tile (REQ-UI-MULTI-SELECT). Sticky for the rest of the drag, so
+    // coming back to the press position does not hide the rectangle again.
+    bool                  m_boxDragMoved;
 
     // Interprets this widget's key events into semantic actions and publishes them
     // (REQ-UI-HOTKEYS). Owned here for now because this is the widget that holds

src/ui/HeaderBar.cpp

@@ -3,7 +3,6 @@
 #include <cmath>
 #include <string>
 
-#include <QFontMetrics>
 #include <QHBoxLayout>
 #include <QIcon>
 #include <QLabel>
@@ -120,19 +119,11 @@ void HeaderBar::handleEvent(std::shared_ptr<const ExpansionCostChangedEvent> /*e
     updateExpandButton();
 }
 
-QPixmap HeaderBar::blockIcon() const
-{
-    if (!m_itemIcons->hasIcon(kBlockItemId)) { return QPixmap(); }
-    // Sized to the header text height so it sits inline with the caption.
-    const int sizePx = QFontMetrics(font()).height();
-    return m_itemIcons->getPixmap(kBlockItemId, sizePx);
-}
-
 void HeaderBar::updateBlocksLabel()
 {
     const int blocks = m_sim->getBuildingBlocksStock();
 
-    const QPixmap icon = blockIcon();
+    const QPixmap icon = m_itemIcons->getInlineIcon(kBlockItemId, font());
     if (icon.isNull())
     {
         // Fallback text form when no building_block icon exists (REQ-UI-BLOCKS-ICON).
@@ -151,7 +142,7 @@ void HeaderBar::updateExpandButton()
 
     m_expandButton->setEnabled(blocks >= expansionCost);
 
-    const QPixmap icon = blockIcon();
+    const QPixmap icon = m_itemIcons->getInlineIcon(kBlockItemId, font());
     if (icon.isNull())
     {
         // Fallback text form when no building_block icon exists (REQ-UI-EXPAND-BUTTON).

src/ui/HeaderBar.h

@@ -61,10 +61,6 @@ private:
     // (REQ-UI-BLOCKS-ICON).
     void updateBlocksLabel();
 
-    // The building_block icon at the header's text height, or a null pixmap when no
-    // icon file exists. Loaded once via m_itemIcons on first use.
-    QPixmap blockIcon() const;
-
     QLabel*                  m_timeLabel;
     QLabel*                  m_blocksLabel;
     QLabel*                  m_artifactsLabel;

src/ui/IconCaption.h

@@ -21,8 +21,11 @@ QPixmap renderCaptionWithIcon(const QString& text, const QPixmap& icon,
 // their raw size is not the size to lay them out at.
 QSize getLogicalSize(const QPixmap& pixmap);
 
-// Item id of the building blocks resource, whose icon stands in for the "Blocks"
-// word wherever a cost or stock is captioned (REQ-UI-BLOCKS-ICON, REQ-UI-BUILD-COST,
-// REQ-UI-EXPAND-BUTTON). It lives next to the caption helper because every caller of
-// one is a caller of the other.
+// The items whose icons stand in for their names beside a number, drawn bare and without
+// their colored square (REQ-UI-ITEM-ICON): building blocks beside a cost or a stock
+// (REQ-UI-BLOCKS-ICON, REQ-UI-BUILD-COST, REQ-UI-EXPAND-BUTTON), and scrap beside the
+// amount left in debris (REQ-UI-DEBRIS-PANEL, REQ-UI-FIELD-MULTI-SELECTION). They live
+// next to the caption helper because every caller of one is a caller of the other;
+// ItemIconCache::getInlineIcon() is what turns an id here into that icon.
 const char* const kBlockItemId = "building_block";
+const char* const kScrapItemId = "scrap";

src/ui/InputMapper.cpp

@@ -9,6 +9,7 @@
 #include "BlueprintSelectionRequestedEvent.h"
 #include "BuildHotkeyPressedEvent.h"
 #include "BuildingType.h"
+#include "ControlAction.h"
 #include "DebugDrawToggleRequestedEvent.h"
 #include "EscapeMenuRequestedEvent.h"
 #include "EventManager.h"
@@ -16,6 +17,7 @@
 #include "ModeCancelRequestedEvent.h"
 #include "PanDirectionChangedEvent.h"
 #include "PauseToggleRequestedEvent.h"
+#include "SelectionClearRequestedEvent.h"
 #include "SpeedStepRequestedEvent.h"
 #include "TemporaryBlueprintCaptureRequestedEvent.h"
 #include "TemporaryBlueprintPlaceRequestedEvent.h"
@@ -77,7 +79,7 @@ QString InputMapper::getBuildHotkeyLabel(BuildingType type)
     return QString();
 }
 
-bool InputMapper::handleKeyPress(QKeyEvent* event)
+bool InputMapper::handleKeyPress(QKeyEvent* event, const ControlContext& context)
 {
     // Auto-repeat says nothing new about which keys are down, and a held action is
     // already held.
@@ -86,6 +88,9 @@ bool InputMapper::handleKeyPress(QKeyEvent* event)
     // Number-key build-mode hotkeys (REQ-UI-HOTKEYS). nativeVirtualKey gives the
     // physical digit independent of keyboard layout and Shift (with Shift held, key()
     // for the number row can arrive as Key_Exclam etc.). VK_1..VK_9 = 0x31..0x39.
+    // Not part of the ControlAction table: these are advertised on the build buttons
+    // rather than in the controls panel, and getBuildHotkeyLabel already reads the
+    // same binding table this does (REQ-UI-CONTROLS-ACCURACY).
     const quint32 virtualKey = event->nativeVirtualKey();
     if (virtualKey >= 0x31 && virtualKey <= 0x39)
     {
@@ -100,107 +105,106 @@ bool InputMapper::handleKeyPress(QKeyEvent* event)
         }
     }
 
-    // Blueprint chords (REQ-UI-HOTKEYS). Checked ahead of the plain-key switch below,
-    // which binds bare A/D/W/S/R/Q/C/V and must not fire on a Ctrl chord -- bare C and V
-    // are the temporary-blueprint counterparts of these two (REQ-UI-BLUEPRINT-TEMP). Both
-    // requests are decided by MainWindow, the only widget that can pause the game and dim
-    // the window for a modal.
-    if ((event->modifiers() & Qt::ControlModifier) != 0)
-    {
-        switch (event->key())
-        {
-        case Qt::Key_C:
-            EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<BlueprintSaveRequestedEvent>());
-            return true;
-        case Qt::Key_V:
-            EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<BlueprintSelectionRequestedEvent>());
-            return true;
-        default:
-            break;
-        }
-    }
-
+    // Development controls, deliberately outside the table so they are never offered
+    // to the player (REQ-UI-CONTROLS-ACCURACY).
     switch (event->key())
     {
-    case Qt::Key_A:
-        m_panLeftHeld = true;
-        updatePanDirection();
-        return true;
-    case Qt::Key_D:
-        m_panRightHeld = true;
-        updatePanDirection();
-        return true;
-    case Qt::Key_Space:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<PauseToggleRequestedEvent>());
-        return true;
-    case Qt::Key_W:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<SpeedStepRequestedEvent>(+1));
-        return true;
-    case Qt::Key_S:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<SpeedStepRequestedEvent>(-1));
-        return true;
-    case Qt::Key_R:
-        // Shift reverses the rotation direction (REQ-BLD-ROTATE).
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<GhostRotationRequestedEvent>(
-                (event->modifiers() & Qt::ShiftModifier) != 0));
-        return true;
-    case Qt::Key_Q:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<ModeCancelRequestedEvent>());
-        return true;
-    case Qt::Key_C:
-        // Capture a temporary blueprint from the current selection (REQ-UI-BLUEPRINT-TEMP).
-        // The BlueprintLibrary owns the selection and blueprint-capture logic; it decides
-        // whether anything placeable is selected and drives placement mode from there.
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<TemporaryBlueprintCaptureRequestedEvent>());
-        return true;
-    case Qt::Key_V:
-        // Re-enter placement mode for the temporary blueprint captured with C, if there is
-        // one (REQ-UI-BLUEPRINT-TEMP). The library holds it; nothing is captured here.
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<TemporaryBlueprintPlaceRequestedEvent>());
-        return true;
     case Qt::Key_F3:
         EventManager::getInstance()->sendEventImmediately(
             std::make_shared<DebugDrawToggleRequestedEvent>());
         return true;
-    case Qt::Key_Escape:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<EscapeMenuRequestedEvent>());
-        return true;
     case Qt::Key_F4:
         EventManager::getInstance()->addEvent(
             std::make_shared<TracePrintRequestedEvent>());
         return true;
     default:
+        break;
+    }
+
+    // Everything else: the key names an action, the action names an event. Which key
+    // is bound to what, and whether it does anything in this situation, are both the
+    // table's business -- this switch only knows what each action means
+    // (REQ-UI-HOTKEYS, REQ-UI-CONTROLS-ACCURACY).
+    switch (resolveKeyAction(event->key(), event->modifiers(), context))
+    {
+    case ControlAction::Move:
+        // A parameter of the action rather than an action of its own: the table binds
+        // both keys to Move and the direction is read off the key here, as the rotation
+        // direction and the build hotkey's digit are.
+        if (event->key() == Qt::Key_A) { m_panLeftHeld = true; }
+        else                           { m_panRightHeld = true; }
+        updatePanDirection();
+        return true;
+    case ControlAction::GameSpeed:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<SpeedStepRequestedEvent>(event->key() == Qt::Key_W ? +1 : -1));
+        return true;
+    case ControlAction::TogglePause:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<PauseToggleRequestedEvent>());
+        return true;
+    case ControlAction::Rotate:
+        // Shift reverses the rotation direction (REQ-BLD-ROTATE).
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<GhostRotationRequestedEvent>(
+                (event->modifiers() & Qt::ShiftModifier) != 0));
+        return true;
+    case ControlAction::EnterDeconstruct:
+    case ControlAction::ExitMode:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<ModeCancelRequestedEvent>());
+        return true;
+    case ControlAction::ClearSelection:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<SelectionClearRequestedEvent>());
+        return true;
+    case ControlAction::CopyTemporary:
+        // The BlueprintLibrary owns the selection and blueprint-capture logic; it drives
+        // placement mode from there (REQ-UI-BLUEPRINT-TEMP).
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<TemporaryBlueprintCaptureRequestedEvent>());
+        return true;
+    case ControlAction::PasteTemporary:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<TemporaryBlueprintPlaceRequestedEvent>());
+        return true;
+    case ControlAction::CreateBlueprint:
+        // Decided by MainWindow, the only widget that can pause the game and dim the
+        // window for a modal.
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<BlueprintSaveRequestedEvent>());
+        return true;
+    case ControlAction::OpenBlueprints:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<BlueprintSelectionRequestedEvent>());
+        return true;
+    case ControlAction::OpenMenu:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<EscapeMenuRequestedEvent>());
+        return true;
+    default:
+        // Either nothing is bound to the key here, or what is bound is a mouse gesture
+        // the view handles. Unconsumed, so ordinary Qt shortcuts keep working.
         return false;
     }
 }
 
-bool InputMapper::handleKeyRelease(QKeyEvent* event)
+bool InputMapper::handleKeyRelease(QKeyEvent* event, const ControlContext& context)
 {
     if (event->isAutoRepeat()) { return false; }
 
-    switch (event->key())
+    // Only held actions have a release worth acting on. Resolved through the table
+    // rather than matched against A and D directly, so the keys stay rebindable in one
+    // place rather than two.
+    if (resolveKeyAction(event->key(), event->modifiers(), context) != ControlAction::Move)
     {
-    case Qt::Key_A:
-        m_panLeftHeld = false;
-        updatePanDirection();
-        return true;
-    case Qt::Key_D:
-        m_panRightHeld = false;
-        updatePanDirection();
-        return true;
-    default:
         return false;
     }
+
+    if (event->key() == Qt::Key_A) { m_panLeftHeld = false; }
+    else                           { m_panRightHeld = false; }
+    updatePanDirection();
+    return true;
 }
 
 void InputMapper::releaseAll()

src/ui/InputMapper.h

@@ -3,14 +3,19 @@
 #include <QString>
 
 #include "BuildingType.h"
+#include "ControlAction.h"
 #include "WorldCamera.h"
 
 class QKeyEvent;
 
 // Turns raw key events into the game's semantic actions and publishes them
 // (REQ-UI-HOTKEYS). Widgets react to the action, never to the key, so the two can
-// be rebound independently later; the bindings themselves are still hard-coded
-// here for now.
+// be rebound independently later.
+//
+// Which key means what is not decided here: the caller hands in a ControlContext and
+// ControlAction.h resolves the press against it, so this file only knows what each
+// action means once resolved. That is what keeps the controls panel and the key
+// handling from drifting apart -- both read the one table (REQ-UI-CONTROLS-ACCURACY).
 //
 // Two output shapes, chosen by the nature of the action rather than by taste:
 //
@@ -34,9 +39,10 @@ public:
     static QString getBuildHotkeyLabel(BuildingType type);
 
     // Both return true when the key was consumed; the caller passes anything else
-    // on to its base class so unrelated shortcuts keep working.
-    bool handleKeyPress(QKeyEvent* event);
-    bool handleKeyRelease(QKeyEvent* event);
+    // on to its base class so unrelated shortcuts keep working. `context` is the
+    // player's current situation, which decides what a key does (REQ-UI-CONTROLS-CONTENT).
+    bool handleKeyPress(QKeyEvent* event, const ControlContext& context);
+    bool handleKeyRelease(QKeyEvent* event, const ControlContext& context);
 
     // Drops all held-key state, publishing the resulting change. Call when the
     // receiving widget can no longer expect key-up events.

src/ui/ItemIconCache.cpp

@@ -1,11 +1,28 @@
 #include "ItemIconCache.h"
 
 #include <QFile>
+#include <QFontMetrics>
 #include <QPainter>
+#include <QRectF>
 #include <QSvgRenderer>
 
-ItemIconCache::ItemIconCache(const QString& iconDir)
+#include "VisualsConfig.h"
+
+namespace
+{
+
+// How far the icon is inset within the item's colored square, as a fraction of the
+// square's size on each side (REQ-UI-ITEM-ICON). The inset is what keeps a frame of the
+// square's color visible all around the icon: each icon's viewBox is cropped tight to
+// its artwork, so an icon drawn at the full rect would cover the square entirely.
+const double kIconInsetFraction = 0.15;
+
+}  // namespace
+
+
+ItemIconCache::ItemIconCache(const QString& iconDir, const VisualsConfig* visuals)
     : m_iconDir(iconDir)
+    , m_visuals(visuals)
 {
 }
 
@@ -34,14 +51,65 @@ bool ItemIconCache::hasIcon(const std::string& itemId)
     return !getSvg(itemId).isEmpty();
 }
 
+void ItemIconCache::paintItem(QPainter& painter, const QRectF& rect,
+                              const std::string& itemId)
+{
+    // The colored square from visuals.toml backs every item, icon or not: it is what
+    // gives the item contrast against the tile beneath it in the world, and its outline
+    // is what separates neighbouring items where they overlap on a belt (REQ-GW-TILE-SIZE,
+    // REQ-UI-ITEM-ICON).
+    if (m_visuals != nullptr)
+    {
+        const std::map<std::string, ItemVisuals>::const_iterator it =
+            m_visuals->items.find(itemId);
+        if (it != m_visuals->items.end())
+        {
+            painter.fillRect(rect, it->second.fill);
+            painter.setPen(QPen(it->second.outline, 1));
+            painter.setBrush(Qt::NoBrush);
+            painter.drawRect(rect);
+        }
+    }
+
+    if (!hasIcon(itemId)) { return; }
+
+    // The icon goes on top, inset so a frame of the square's color stays visible all
+    // around it. It is rasterized once at the inset pixel size and cached, so this is a
+    // plain pixmap blit per frame.
+    const double inset = kIconInsetFraction * rect.width();
+    const QRectF iconRect = rect.adjusted(inset, inset, -inset, -inset);
+
+    int sizePx = qRound(iconRect.width());
+    if (sizePx < 1) { sizePx = 1; }
+    painter.drawPixmap(iconRect, getPixmap(itemId, sizePx),
+                       QRectF(0, 0, sizePx, sizePx));
+}
+
+QPixmap ItemIconCache::getSquarePixmap(const std::string& itemId, int sizePx)
+{
+    return getPixmap("square:" + itemId, itemId, sizePx, true);
+}
+
 QPixmap ItemIconCache::getPixmap(const std::string& itemId, int sizePx)
+{
+    return getPixmap(itemId, itemId, sizePx, false);
+}
+
+QPixmap ItemIconCache::getInlineIcon(const std::string& itemId, const QFont& font)
+{
+    if (!hasIcon(itemId)) { return QPixmap(); }
+    return getPixmap(itemId, QFontMetrics(font).height());
+}
+
+QPixmap ItemIconCache::getPixmap(const std::string& cacheKey, const std::string& itemId,
+                                 int sizePx, bool withSquare)
 {
     if (sizePx <= 0)
     {
         return QPixmap();
     }
 
-    const std::pair<std::string, int> key(itemId, sizePx);
+    const std::pair<std::string, int> key(cacheKey, sizePx);
     const std::map<std::pair<std::string, int>, QPixmap>::const_iterator cached =
         m_pixmapCache.find(key);
     if (cached != m_pixmapCache.end())
@@ -49,16 +117,45 @@ QPixmap ItemIconCache::getPixmap(const std::string& itemId, int sizePx)
         return cached->second;
     }
 
-    const QByteArray& svg = getSvg(itemId);
     QPixmap pixmap;
-    if (!svg.isEmpty())
+    if (withSquare)
     {
-        QSvgRenderer renderer(svg);
-        pixmap = QPixmap(sizePx, sizePx);
-        pixmap.fill(Qt::transparent);
-        QPainter painter(&pixmap);
-        painter.setRenderHint(QPainter::Antialiasing, true);
-        renderer.render(&painter);
+        // Null unless the item has something to draw -- a square, an icon, or both --
+        // so a caller with nothing to show can fall back to text (REQ-UI-ITEM-ICON).
+        const bool hasSquare = m_visuals != nullptr
+            && m_visuals->items.find(itemId) != m_visuals->items.end();
+        if (hasSquare || hasIcon(itemId))
+        {
+            pixmap = QPixmap(sizePx, sizePx);
+            pixmap.fill(Qt::transparent);
+            QPainter painter(&pixmap);
+            // No antialiasing: the square's edges are axis-aligned and land on pixel
+            // boundaries, and smoothing a 1-pixel outline only blurs it. The icon is
+            // blitted into a slightly smaller rect than it was rasterized at, which is
+            // what the smooth transform is for.
+            painter.setRenderHint(QPainter::SmoothPixmapTransform, true);
+            // One pixel short of the pixmap so the square's right and bottom edges land
+            // inside it rather than on its border.
+            paintItem(painter, QRectF(0, 0, sizePx - 1, sizePx - 1), itemId);
+        }
+    }
+    else
+    {
+        const QByteArray& svg = getSvg(itemId);
+        if (!svg.isEmpty())
+        {
+            QSvgRenderer renderer(svg);
+            pixmap = QPixmap(sizePx, sizePx);
+            pixmap.fill(Qt::transparent);
+            QPainter painter(&pixmap);
+            painter.setRenderHint(QPainter::Antialiasing, true);
+            renderer.render(&painter);
+        }
     }
     return m_pixmapCache.emplace(key, std::move(pixmap)).first->second;
 }
+
+void ItemIconCache::clearPixmapCache()
+{
+    m_pixmapCache.clear();
+}

src/ui/ItemIconCache.h

@@ -5,41 +5,89 @@
 #include <utility>
 
 #include <QByteArray>
+#include <QFont>
 #include <QPixmap>
 #include <QString>
 
-// Rasterizes and caches per-item icon SVGs (REQ-UI-ITEM-ICON). Item icons are
-// self-contained, full-color SVGs loaded from a directory, one file per item type
-// named after the item's id (e.g. "iron_ore.svg"). Shared by the recipe-selection
-// dialog (REQ-UI-RECIPE-ICON) and the game world's belt/port item rendering so the
-// rasterization is not duplicated.
+class QPainter;
+class QRectF;
+struct VisualsConfig;
+
+// Rasterizes and caches per-item icon SVGs, and composes them onto the item's colored
+// square (REQ-UI-ITEM-ICON). Item icons are self-contained, full-color SVGs loaded from
+// a directory, one file per item type named after the item's id (e.g. "iron_ore.svg").
 //
-// A missing icon file is not an error: hasIcon() returns false for it and the caller
-// falls back (a colored square in the world, a name caption in the dialog).
+// The square is the item's `fill` and `outline` from visuals.toml with the icon inset
+// within it, and it backs the icon both in the game world and wherever the UI displays
+// an item as an item: the selection panel's item chips (REQ-UI-SINGLE-SELECTION,
+// REQ-UI-HQ-PANEL), and every recipe drawn as a line -- the recipe summary, the
+// selection dialog's option buttons, the item production tooltip
+// (REQ-UI-RECIPE-SUMMARY, REQ-UI-SELECT-OPTIONS, REQ-UI-ITEM-TOOLTIP). Defined here
+// once rather than per widget, in
+// two forms: paintItem() for the world's fractional geometry, getSquarePixmap() for
+// widgets that want a ready-made pixmap.
+//
+// The bare icon of getPixmap() has one remaining use: an inline icon standing in for the
+// item's name beside a number -- building blocks beside a cost or a stock
+// (REQ-UI-BLOCKS-ICON), scrap beside the amount left in debris (REQ-UI-DEBRIS-PANEL) --
+// which is a decoration on a line of text rather than an item display and takes no
+// square. getInlineItemIcon() in IconCaption.h is how callers ask for that form.
+//
+// A missing icon file is not an error: hasIcon() returns false for it and the item shows
+// its colored square alone.
 class ItemIconCache
 {
 public:
-    // iconDir is the directory holding the "<item_id>.svg" icon files
-    // (typically "<configDir>/../icons/items").
-    explicit ItemIconCache(const QString& iconDir);
+    // iconDir is the directory holding the "<item_id>.svg" icon files (typically
+    // "<configDir>/../icons/items"). visuals supplies the per-item square colors and
+    // must outlive the cache; its contents may be replaced on a restart (REQ-CFG-RELOAD),
+    // which is what clearPixmapCache() is for.
+    ItemIconCache(const QString& iconDir, const VisualsConfig* visuals);
 
     // True if an icon SVG file exists for the given item id. Loads the file's bytes
     // on first query and remembers the result (including absence) so repeated calls
     // are cheap.
     bool hasIcon(const std::string& itemId);
 
-    // Returns the item's icon rasterized to a transparent sizePx*sizePx pixmap,
-    // cached per (item id, size) so it is rendered once and reused across frames and
-    // only re-rasterized when the target size changes (REQ-UI-ITEM-ICON). Returns a
-    // null pixmap if the item has no icon file (callers should gate on hasIcon()).
+    // Paints the item's colored square into rect and its icon inset within it
+    // (REQ-UI-ITEM-ICON). Takes the rect as a QRectF so the world can keep painting at
+    // sub-pixel geometry. An item with no visuals entry gets no square, one with no icon
+    // file no icon; with neither, this paints nothing.
+    void paintItem(QPainter& painter, const QRectF& rect, const std::string& itemId);
+
+    // The same composition rasterized to a sizePx*sizePx pixmap for widget use, cached
+    // per (item id, size) so it is rendered once and reused. Returns a null pixmap only
+    // when the item has neither a visuals entry nor an icon file, which is the one case
+    // in which a caller has nothing to show and falls back to text.
+    QPixmap getSquarePixmap(const std::string& itemId, int sizePx);
+
+    // Returns the item's icon alone, without its square, rasterized to a transparent
+    // sizePx*sizePx pixmap and cached per (item id, size) so it is rendered once and
+    // reused across frames (REQ-UI-ITEM-ICON). Returns a null pixmap if the item has no
+    // icon file (callers should gate on hasIcon()).
     QPixmap getPixmap(const std::string& itemId, int sizePx);
 
+    // The same bare icon sized to the height of `font`'s text, for the inline form above:
+    // an icon standing in for the item's name on a line of text. Null when the item has
+    // no icon file, which is not an error -- the caller names the item in words instead.
+    QPixmap getInlineIcon(const std::string& itemId, const QFont& font);
+
+    // Drops every rasterized pixmap. Called when the visuals are reloaded on a restart
+    // (REQ-CFG-RELOAD), because the composed squares carry the colors they were painted
+    // with; they are re-rasterized on next use.
+    void clearPixmapCache();
+
 private:
     // Returns the raw SVG bytes for an item id, loading and caching them on first
     // access. An absent file caches an empty QByteArray so it is not retried.
     const QByteArray& getSvg(const std::string& itemId);
+    // Shared rasterize-and-cache step. cacheKey distinguishes the bare and squared
+    // variants of one item within the single pixmap cache.
+    QPixmap getPixmap(const std::string& cacheKey, const std::string& itemId,
+                      int sizePx, bool withSquare);
 
     QString                            m_iconDir;
+    const VisualsConfig*               m_visuals;  // Not owned; lives in MainWindow.
     std::map<std::string, QByteArray>  m_svgById;
     std::map<std::pair<std::string, int>, QPixmap> m_pixmapCache;
 };

src/ui/ItemProducers.cpp

@@ -0,0 +1,48 @@
+#include "ItemProducers.h"
+
+#include "GameConfig.h"
+#include "RecipesConfig.h"
+#include "Simulation.h"
+
+namespace
+{
+
+bool isAvailable(const RecipeDef& recipe, const Simulation& sim)
+{
+    if (recipe.building == BuildingType::Miner
+        || recipe.building == BuildingType::Assembler)
+    {
+        return sim.isRecipeUnlocked(recipe.id);
+    }
+    return sim.isBuildingUnlocked(recipe.building);
+}
+
+}  // namespace
+
+ItemProduction findItemProduction(const std::string& itemId, const Simulation& sim,
+                                  const GameConfig& config)
+{
+    ItemProduction result;
+
+    bool anyProducer = false;
+    for (const RecipeDef& recipe : config.recipes.recipes)
+    {
+        if (!producesItem(recipe, itemId)) { continue; }
+
+        anyProducer = true;
+        if (isAvailable(recipe, sim))
+        {
+            result.recipes.push_back(&recipe);
+        }
+    }
+
+    if (!result.recipes.empty())
+    {
+        result.origin = ItemOrigin::Produced;
+    }
+    else
+    {
+        result.origin = anyProducer ? ItemOrigin::Undiscovered : ItemOrigin::Salvaged;
+    }
+    return result;
+}

src/ui/ItemProducers.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+struct GameConfig;
+struct RecipeDef;
+class Simulation;
+
+// Where an item comes from, as far as the player has discovered (REQ-UI-ITEM-TOOLTIP).
+enum class ItemOrigin
+{
+    Produced,      // at least one recipe the player can run makes it
+    Undiscovered,  // recipes make it, but none of them is available yet
+    Salvaged,      // no recipe makes it at all -- scrap, which comes from debris
+};
+
+struct ItemProduction
+{
+    ItemOrigin                    origin = ItemOrigin::Salvaged;
+    // The available producers, in config order. Empty unless origin is Produced.
+    std::vector<const RecipeDef*> recipes;
+};
+
+// Every way the player can currently produce the given item, for the tooltip that
+// explains an item chip (REQ-UI-ITEM-TOOLTIP).
+//
+// What counts as available differs by building type, because only Miner and Assembler
+// recipes are individually unlocked (REQ-LOCK-UI-RECIPE): those are filtered by the
+// unlock state, while a Smelter's or Reprocessing Plant's recipes
+// (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING) are filtered by whether their building is
+// unlocked yet (REQ-LOCK-BUILDING) -- there is no sense in naming a path through a
+// plant the player cannot place.
+ItemProduction findItemProduction(const std::string& itemId, const Simulation& sim,
+                                  const GameConfig& config);

src/ui/MainWindow.cpp

@@ -7,6 +7,7 @@
 
 #include <QApplication>
 #include <QCloseEvent>
+#include <QDialog>
 #include <QDir>
 #include <QFile>
 #include <QInputDialog>
@@ -28,9 +29,11 @@
 #include "RecipeSelectionDialog.h"
 #include "SchematicChoiceDialog.h"
 #include "HeaderBar.h"
-#include "SelectedBuildingPanel.h"
+#include "SelectionPanel.h"
+#include "ControlsPanel.h"
 #include "ShipLayoutBlueprintSerializer.h"
 #include "ShipLayoutDialog.h"
+#include "BuildingIconCache.h"
 #include "ItemIconCache.h"
 #include "ModalPauseScope.h"
 #include "Simulation.h"
@@ -48,55 +51,52 @@ MainWindow::MainWindow(Simulation* sim, const std::string& configDir,
     setWindowTitle(tr("Dota Factory"));
     resize(1280, 768);
 
-    // Item icons live alongside the config (a sibling of the config dir), read from
-    // disk at runtime like the building icons and visuals.toml (REQ-UI-ITEM-ICON).
-    const std::string itemsIconDir = QDir::cleanPath(
-        QString::fromStdString(m_configDir) + "/../icons/items").toStdString();
-
+    // Item and building icons live alongside the config (siblings of the config dir),
+    // read from disk at runtime the same way visuals.toml is (REQ-UI-ITEM-ICON,
+    // REQ-UI-BUILD-ICON).
+    const QString configDirPath = QString::fromStdString(m_configDir);
     m_itemIcons = std::make_unique<ItemIconCache>(
-        QString::fromStdString(itemsIconDir));
+        QDir::cleanPath(configDirPath + "/../icons/items"), &m_visuals);
+    m_buildingIcons = std::make_unique<BuildingIconCache>(
+        QDir::cleanPath(configDirPath + "/../icons/buildings"));
 
     m_headerBar = new HeaderBar(sim, &sim->getConfig(), m_itemIcons.get(), this);
 
     m_gameWorldView = new GameWorldView(sim, &sim->getConfig(), &m_visuals, m_configDir,
                                         m_itemIcons.get(), m_replay.get(), this);
 
-    // Building icons live alongside the config (a sibling of the config dir), read
-    // from disk at runtime the same way visuals.toml is.
-    const std::string iconDir = QDir::cleanPath(
-        QString::fromStdString(m_configDir) + "/../icons/buildings").toStdString();
-
-    // Floats over the game world rather than living in the side panel column
+    // Floats over the game world at its bottom center, sized to its buttons
     // (REQ-UI-BUILD-BAR). Creation order is the stacking order for siblings, so
     // building it after the world view puts it above the world and its vignettes,
     // and before the dim overlay keeps modals dimming it too (REQ-UI-MODAL-DIM).
     // Its geometry comes from layoutPanels().
-    m_buildButtonBar = new BuildButtonBar(sim, &sim->getConfig(), iconDir,
-                                          m_itemIcons.get(), this);
+    m_buildButtonBar = new BuildButtonBar(sim, &sim->getConfig(),
+                                          m_buildingIcons.get(), m_itemIcons.get(),
+                                          this);
 
     // The blueprints have no widget of their own: they are saved with Ctrl+C and picked
     // from a modal dialog (REQ-UI-BLUEPRINT-DIALOG), both driven from this window
     // because only it can pause the game and raise the dim overlay. Built after the
     // world view because loading blueprints.toml may put a message box on screen.
     m_blueprintLibrary = std::make_unique<BlueprintLibrary>(sim, &sim->getConfig(), this);
+    // Two facts about blueprints decide what the world view offers the player
+    // (REQ-UI-CONTROLS-CONTENT); the library is built after the view, so it is handed
+    // over here rather than passed to the constructor.
+    m_gameWorldView->setBlueprintLibrary(m_blueprintLibrary.get());
 
-    m_sidePanel = new QWidget(this);
-    QVBoxLayout* sideLayout = new QVBoxLayout(m_sidePanel);
-    sideLayout->setContentsMargins(1, 1, 1, 1);
-    sideLayout->setSpacing(1);
+    // Floats over the game world at its right edge rather than occupying a column of
+    // its own, and hides itself while nothing is selected (REQ-UI-SELECTION-PANEL). Like
+    // the build button bar it is a sibling of the world view built after it, which is
+    // what puts it above the world and its vignettes and below the dim overlay. It
+    // brings its own chrome; its geometry comes from layoutPanels().
+    m_selectionPanel = new SelectionPanel(sim, &sim->getConfig(), &m_visuals,
+                                          m_itemIcons.get(), m_buildingIcons.get(),
+                                          this);
 
-    // The selected building panel is the column's only panel and fills its height
-    // (REQ-UI-PANEL-COLUMN).
-    m_selectedBuildingPanel = new SelectedBuildingPanel(sim, &sim->getConfig(), m_sidePanel);
-    sideLayout->addWidget(m_selectedBuildingPanel, 1);
-
-    // Draw a thin border around the side panel section. The class scoped selector keeps
-    // the border on the panel itself rather than cascading onto its child widgets;
-    // WA_StyledBackground lets the plain QWidget subclass honor the stylesheet box
-    // (border/background).
-    m_selectedBuildingPanel->setAttribute(Qt::WA_StyledBackground, true);
-    m_sidePanel->setStyleSheet(QStringLiteral(
-        "SelectedBuildingPanel { border: 1px solid palette(mid); }"));
+    // Floats at the world view's opposite edge from the selection panel and reads the
+    // world view for the player's current situation (REQ-UI-CONTROLS-PANEL). Built
+    // after the view for the same stacking reason as the panels above it.
+    m_controlsPanel = new ControlsPanel(m_gameWorldView, this);
 
     // Created last so it stacks above the other children; covers the whole window and
     // dims the game behind modal dialogs/menus (REQ-UI-MODAL-DIM).
@@ -166,16 +166,57 @@ void MainWindow::layoutPanels()
     const int totalH  = height();
     const int headerH = m_headerBar->sizeHint().height();
     if (headerH <= 0) { return; }
-    const int mainW = totalW * 75 / 100;
-    const int sideW = totalW - mainW;
 
-    m_headerBar->setGeometry(0, 0, mainW, headerH);
-    m_gameWorldView->setGeometry(0, headerH, mainW, totalH - headerH);
-    m_sidePanel->setGeometry(mainW, 0, sideW, totalH);
-    // Sizes itself to its buttons and centers along the bottom of the world view
-    // (REQ-UI-BUILD-BAR).
-    m_buildButtonBar->anchorTo(QRect(0, headerH, mainW, totalH - headerH));
+    // Header bar and game world view span the full window width; the two floating
+    // widgets below are the only things over the world (REQ-UI-HEADER,
+    // REQ-UI-WORLD-SIZE).
+    const QRect worldRect(0, headerH, totalW, totalH - headerH);
+    m_headerBar->setGeometry(0, 0, totalW, headerH);
+    m_gameWorldView->setGeometry(worldRect);
     m_dimOverlay->setGeometry(0, 0, totalW, totalH);
+
+    // The floating widgets are placed in one ordered pass, each into the space the
+    // earlier ones have not taken (FloatingPanel.h). The order is the priority the
+    // requirements state: the build button bar takes what it wants and never moves for
+    // anyone (REQ-UI-BUILD-BAR), the controls panel steps around the bar
+    // (REQ-UI-CONTROLS-PANEL), and the selection panel keeps clear of both
+    // (REQ-UI-SELECTION-PANEL). A widget with nothing to show hides itself in placeIn()
+    // and takes no space.
+    //
+    // Re-entry is refused rather than queued: setGeometry() on a widget in the pass can
+    // reach code that asks for another pass, and the one already running is about to
+    // produce the same answer.
+    if (m_layingOut)
+    {
+        return;
+    }
+    m_layingOut = true;
+
+    const std::vector<QWidget*> floatingWidgets = {
+        m_buildButtonBar, m_controlsPanel, m_selectionPanel };
+    const std::vector<FloatingPanel*> floatingPanels = {
+        m_buildButtonBar, m_controlsPanel, m_selectionPanel };
+
+    std::vector<QRect> occupiedRects;
+    for (std::size_t i = 0; i < floatingPanels.size(); ++i)
+    {
+        floatingPanels[i]->placeIn(worldRect, occupiedRects);
+        if (floatingWidgets[i]->isVisible())
+        {
+            occupiedRects.push_back(floatingWidgets[i]->geometry());
+        }
+    }
+
+    m_layingOut = false;
+}
+
+void MainWindow::handleEvent(
+    std::shared_ptr<const FloatingLayoutInvalidatedEvent> /*event*/)
+{
+    // One of the floating widgets changed size or visibility. What each of them may take
+    // depends on the ones placed before it, so the answer is the whole pass rather than
+    // that one widget re-placing itself.
+    layoutPanels();
 }
 
 void MainWindow::handleEvent(std::shared_ptr<const SchematicChoicesAvailableEvent> event)
@@ -183,9 +224,15 @@ void MainWindow::handleEvent(std::shared_ptr<const SchematicChoicesAvailableEven
     ModalPauseScope pause(*m_gameWorldView);
 
     ModalDimScope dim(*m_dimOverlay);
-    SchematicChoiceDialog dialog(event->choices, m_sim->getConfig().recipes, this);
+    SchematicChoiceDialog dialog(event->choices, m_sim->getConfig().recipes,
+                                 m_itemIcons.get(), m_buildingIcons.get(), this);
     dialog.exec();
 
+    // The command goes out unconditionally because the dialog cannot be dismissed: it
+    // returns only once an option was clicked, so the index always names that option
+    // (REQ-DEF-SCHEMATIC-DROP). It is also the only thing that resolves the drop -- the
+    // poll that opened this dialog will not open it again while the choices stay pending
+    // (GameWorldView::onFrame) -- so a path that skipped the command would strand it.
     std::shared_ptr<ApplySchematicChoiceCommand> command =
         std::make_shared<ApplySchematicChoiceCommand>();
     command->choiceIndex = dialog.getChosenIndex();
@@ -243,6 +290,9 @@ std::optional<GameConfig> MainWindow::reloadConfig()
         VisualsConfig newVisuals = VisualsLoader::load(m_configDir + "/visuals.toml");
         m_visuals = std::move(newVisuals);
         m_dimOverlay->setDimColor(m_visuals.overlays.modalDim);
+        // The composed item squares carry the colors they were painted with, so they
+        // are dropped for the new ones to take effect (REQ-UI-ITEM-ICON).
+        m_itemIcons->clearPixmapCache();
         return newConfig;
     }
     catch (const std::exception& e)
@@ -273,7 +323,10 @@ void MainWindow::openShipLayoutDialog(BuildingId shipyardId,
                             m_layoutBlueprints,
                             std::move(unlockedModuleIds),
                             m_gameWorldView->isDebugDrawEnabled(),
-                            this);
+                            m_itemIcons.get(), this);
+    // Opened from the panel's "Configure" button (REQ-MOD-UI-PREVIEW) or straight after
+    // a schematic change (REQ-MOD-UI-AUTO-DIALOG), so it opens on the panel either way.
+    placeOnSelectionPanel(dialog);
     if (dialog.exec() == QDialog::Accepted && dialog.getResult().has_value())
     {
         std::shared_ptr<SetShipLayoutCommand> command =
@@ -285,6 +338,45 @@ void MainWindow::openShipLayoutDialog(BuildingId shipyardId,
     }
 }
 
+void MainWindow::placeOnSelectionPanel(QDialog& dialog) const
+{
+    // The panel is up whenever one of these modals opens -- they are opened from its own
+    // controls, and it is shown whenever anything is selected (REQ-UI-EMPTY-SELECTION).
+    // Were it not, there would be no rectangle to center on and Qt's own centering on
+    // this window stands.
+    if (!m_selectionPanel->isVisible()) { return; }
+
+    // The dialog has never been shown, so it is still at its default size until its
+    // layout has run; centering it before that would use the wrong extent.
+    dialog.adjustSize();
+    const QSize dialogSize = dialog.size();
+
+    // The panel's live geometry, so a panel the player has dragged
+    // (REQ-UI-SELECTION-PANEL-DRAG) carries the modal with it.
+    const QRect panelRect(m_selectionPanel->mapToGlobal(QPoint(0, 0)),
+                          m_selectionPanel->size());
+    const QRect windowRect(mapToGlobal(QPoint(0, 0)), size());
+
+    QPoint topLeft(panelRect.center().x() - dialogSize.width() / 2,
+                   panelRect.center().y() - dialogSize.height() / 2);
+
+    // Pushed back inside the window, never resized to fit (REQ-UI-PANEL-MODAL). The far
+    // edge is clamped first and the near edge second, which is what aligns a dialog too
+    // large for the window with the window's top-left corner rather than pushing it off
+    // the opposite edge.
+    topLeft.setX(qMax(windowRect.left(),
+                      qMin(topLeft.x(), windowRect.right() - dialogSize.width() + 1)));
+    topLeft.setY(qMax(windowRect.top(),
+                      qMin(topLeft.y(), windowRect.bottom() - dialogSize.height() + 1)));
+
+    // Positions the dialog's frame, whose size is not known until it is first shown, so
+    // the result sits low by the title bar height against a true center -- measuring it
+    // would mean showing the dialog at the wrong place first. The move also marks the
+    // dialog as positioned, which is what stops QDialog from centering it on this window
+    // when it is shown.
+    dialog.move(topLeft);
+}
+
 void MainWindow::handleEvent(std::shared_ptr<const LayoutDialogRequestedEvent> event)
 {
     // A construction site has no Building yet; fall back to its site record so
@@ -298,6 +390,15 @@ void MainWindow::handleEvent(std::shared_ptr<const LayoutDialogRequestedEvent> e
     }
 
     const std::string& schematicId = b ? b->recipeId : s->recipeId;
+    // Nothing to configure without a schematic and a grid to place modules on. The
+    // Configure button that publishes this is already disabled then (REQ-MOD-UI-PREVIEW),
+    // so this guards the event rather than the button: the dialog would otherwise open
+    // over a grid of no cells.
+    if (!m_sim->getConfig().ships.findLayoutShipDef(schematicId))
+    {
+        return;
+    }
+
     const std::optional<ShipLayoutConfig>& layoutOpt =
         b ? b->shipLayout : s->shipLayout;
 
@@ -341,7 +442,9 @@ void MainWindow::handleEvent(std::shared_ptr<const RecipeSelectionRequestedEvent
 
     bool autoOpenLayout = false;
     std::string chosenSchematic;
-    RecipeSelectionDialog dialog(options, title, m_itemIcons.get(), this);
+    RecipeSelectionDialog dialog(options, title, m_itemIcons.get(),
+                                 m_buildingIcons.get(), this);
+    placeOnSelectionPanel(dialog);
     if (dialog.exec() == QDialog::Accepted && dialog.getChosenId().has_value())
     {
         std::shared_ptr<SetRecipeCommand> command = std::make_shared<SetRecipeCommand>();
@@ -351,8 +454,12 @@ void MainWindow::handleEvent(std::shared_ptr<const RecipeSelectionRequestedEvent
             std::make_shared<CommandRequestedEvent>(command));
 
         // REQ-MOD-UI-AUTO-DIALOG: picking a new schematic for a shipyard opens the
-        // layout configuration dialog immediately. Only on an actual change.
-        if (type == BuildingType::Shipyard && *dialog.getChosenId() != oldSchematic)
+        // layout configuration dialog immediately. Only on an actual change, and only
+        // for an actual schematic: "(None)" clears the shipyard and carries the empty
+        // id (REQ-UI-SELECT-OPTIONS), which differs from whatever was set but is not a
+        // schematic to configure.
+        if (type == BuildingType::Shipyard && *dialog.getChosenId() != oldSchematic
+            && m_sim->getConfig().ships.findLayoutShipDef(*dialog.getChosenId()))
         {
             autoOpenLayout = true;
             chosenSchematic = *dialog.getChosenId();

src/ui/MainWindow.h

@@ -12,6 +12,7 @@
 #include "BuildingId.h"
 #include "EscapeMenuRequestedEvent.h"
 #include "EventHandler.h"
+#include "FloatingLayoutInvalidatedEvent.h"
 #include "GameConfig.h"
 #include "GameOverEvent.h"
 #include "LayoutDialogRequestedEvent.h"
@@ -28,11 +29,14 @@ struct ParsedReplay;
 class Simulation;
 class GameWorldView;
 class HeaderBar;
-class SelectedBuildingPanel;
+class SelectionPanel;
+class ControlsPanel;
 class BuildButtonBar;
 class BlueprintLibrary;
+class BuildingIconCache;
 class ItemIconCache;
 class QCloseEvent;
+class QDialog;
 class QResizeEvent;
 
 class MainWindow : public QWidget,
@@ -43,7 +47,8 @@ class MainWindow : public QWidget,
                                                LayoutDialogRequestedEvent,
                                                RecipeSelectionRequestedEvent,
                                                BlueprintSaveRequestedEvent,
-                                               BlueprintSelectionRequestedEvent>
+                                               BlueprintSelectionRequestedEvent,
+                                               FloatingLayoutInvalidatedEvent>
 {
     Q_OBJECT
 
@@ -65,6 +70,7 @@ private:
     void handleEvent(std::shared_ptr<const RecipeSelectionRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const BlueprintSaveRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const BlueprintSelectionRequestedEvent> event) override;
+    void handleEvent(std::shared_ptr<const FloatingLayoutInvalidatedEvent> event) override;
 
     // Reloads the game config and visuals.toml from disk (REQ-CFG-RELOAD), shared
     // by every restart path. On success the reloaded visuals are applied to this
@@ -78,11 +84,18 @@ private:
                               const std::string& schematicId,
                               const ShipLayoutConfig& currentLayout);
 
+    // Centers a modal opened from the selection panel on that panel, kept inside this
+    // window (REQ-UI-PANEL-MODAL). Called on the constructed dialog before exec(), and
+    // only for the two modals the panel opens.
+    void placeOnSelectionPanel(QDialog& dialog) const;
+
     // Runs the blueprint selection dialog and enters placement mode for whatever the
     // player picked (REQ-UI-BLUEPRINT-DIALOG). Holds no pause or dim scope of its own:
     // both callers already hold theirs, which is what keeps the dim continuous when a
     // confirmed save hands straight over to this dialog (REQ-UI-MODAL-DIM).
     void showBlueprintSelectionDialog();
+    // Places the widgets floating over the game world view, in one ordered pass
+    // (FloatingPanel.h). Runs on a resize and on every FloatingLayoutInvalidatedEvent.
     void layoutPanels();
 
 private:
@@ -92,16 +105,23 @@ private:
     // One per-item icon cache for the whole window (REQ-UI-ITEM-ICON): the header,
     // build bar, world view, and recipe dialog all rasterize the same SVGs.
     std::unique_ptr<ItemIconCache> m_itemIcons;
+    // Likewise one per-building chip cache (REQ-UI-BUILD-ICON), shared by the build bar
+    // and the selection panel's card headers (REQ-UI-SELECTION-CARD).
+    std::unique_ptr<BuildingIconCache> m_buildingIcons;
     GameWorldView*         m_gameWorldView;
     HeaderBar*             m_headerBar;
-    SelectedBuildingPanel* m_selectedBuildingPanel;
+    SelectionPanel*        m_selectionPanel;
+    ControlsPanel*         m_controlsPanel;
     BuildButtonBar*        m_buildButtonBar;
     // The saved blueprints themselves; they have no widget of their own any more and
     // are reached through the two modal dialogs (REQ-UI-BLUEPRINT-DIALOG).
     std::unique_ptr<BlueprintLibrary> m_blueprintLibrary;
-    QWidget*               m_sidePanel;
     ModalDimOverlay*       m_dimOverlay = nullptr;
 
     std::vector<ShipLayoutBlueprint> m_layoutBlueprints;
     std::shared_ptr<ParsedReplay>    m_replay;  // non-null => view-only playback
+
+    // Set while the placement pass runs, so a widget placed in it cannot start a second
+    // pass from inside the first.
+    bool m_layingOut = false;
 };

src/ui/OptionButton.cpp

@@ -0,0 +1,35 @@
+#include "OptionButton.h"
+
+#include <QLayout>
+#include <QStyle>
+#include <QStyleOptionButton>
+
+OptionButton::OptionButton(QWidget* parent)
+    : QPushButton(parent)
+{
+}
+
+QSize OptionButton::sizeHint() const
+{
+    if (layout() == nullptr)
+    {
+        return QPushButton::sizeHint();
+    }
+    return sizeForFace(layout()->sizeHint());
+}
+
+QSize OptionButton::minimumSizeHint() const
+{
+    if (layout() == nullptr)
+    {
+        return QPushButton::minimumSizeHint();
+    }
+    return sizeForFace(layout()->minimumSize());
+}
+
+QSize OptionButton::sizeForFace(const QSize& faceSize) const
+{
+    QStyleOptionButton option;
+    initStyleOption(&option);
+    return style()->sizeFromContents(QStyle::CT_PushButton, &option, faceSize, this);
+}

src/ui/OptionButton.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <QPushButton>
+#include <QSize>
+
+// A push button whose face is built of widgets rather than of a caption: an option's
+// name over the recipe line stating what it makes (REQ-UI-SELECT-OPTIONS), or a module's
+// name over what it costs (REQ-MOD-UI-DIALOG).
+//
+// It exists only to be measured correctly. QPushButton computes its size hint from its
+// text and icon and ignores a layout set on it, so a button carrying a face of widgets
+// would be sized as if it were empty and clip everything in it. This asks the layout
+// instead, and then lets the style add what the button's own frame needs.
+class OptionButton : public QPushButton
+{
+    Q_OBJECT
+
+public:
+    explicit OptionButton(QWidget* parent = nullptr);
+
+    QSize sizeHint() const override;
+    QSize minimumSizeHint() const override;
+
+private:
+    // The style's button size for the given face size, or the plain QPushButton hint
+    // when there is no face to measure.
+    QSize sizeForFace(const QSize& faceSize) const;
+};

src/ui/RecipeLineRow.cpp

@@ -0,0 +1,223 @@
+#include "RecipeLineRow.h"
+
+#include <QFont>
+#include <QHBoxLayout>
+#include <QLabel>
+#include <QLayoutItem>
+#include <QMargins>
+#include <QPixmap>
+#include <QVBoxLayout>
+
+#include "BuildingIconCache.h"
+#include "ItemIconCache.h"
+
+namespace
+{
+
+// Size the items' colored squares and the building's chip are drawn at on a line, in
+// device-independent pixels. Larger than the artwork they carry, which the square
+// insets (REQ-UI-ITEM-ICON).
+const int kIconSizePx = 18;
+
+// Adds a freshly built label to the line and shows it.
+//
+// The show is what makes it count: a widget created under an already-visible parent
+// starts hidden, and a layout treats a hidden item as empty, so an unshown label would
+// add nothing to the size hint the surrounding widget measures itself against as soon
+// as this returns.
+void addAndShow(QHBoxLayout* layout, QLabel* label)
+{
+    layout->addWidget(label);
+    label->show();
+}
+
+// Empties one of the two rows, leaving the row widget and its layout in place.
+void clearRow(QHBoxLayout* layout)
+{
+    while (QLayoutItem* item = layout->takeAt(0))
+    {
+        if (item->widget())
+        {
+            item->widget()->deleteLater();
+        }
+        delete item;
+    }
+}
+
+}  // namespace
+
+
+std::vector<std::vector<RecipeLineRow::Amount>> RecipeLineRow::toOutputGroups(
+    const RecipeDef& recipe)
+{
+    std::vector<std::vector<Amount>> groups;
+    groups.reserve(recipe.outputGroups.size());
+    for (const RecipeOutputGroup& group : recipe.outputGroups)
+    {
+        std::vector<Amount> amounts;
+        amounts.reserve(group.items.size());
+        for (const RecipeOutput& out : group.items)
+        {
+            amounts.push_back(Amount{ out.item, out.amount });
+        }
+        groups.push_back(std::move(amounts));
+    }
+    return groups;
+}
+
+RecipeLineRow::RecipeLineRow(ItemIconCache* itemIcons, BuildingIconCache* buildingIcons,
+                             QWidget* parent)
+    : QWidget(parent)
+    , m_itemIcons(itemIcons)
+    , m_buildingIcons(buildingIcons)
+{
+    m_outerLayout = new QVBoxLayout(this);
+    m_outerLayout->setContentsMargins(0, 0, 0, 0);
+    m_outerLayout->setSpacing(1);
+
+    m_headerRow    = new QWidget(this);
+    m_headerLayout = new QHBoxLayout(m_headerRow);
+    m_headerLayout->setContentsMargins(0, 0, 0, 0);
+    m_headerLayout->setSpacing(4);
+    m_headerRow->hide();
+    m_outerLayout->addWidget(m_headerRow);
+
+    m_amountsRow    = new QWidget(this);
+    m_amountsLayout = new QHBoxLayout(m_amountsRow);
+    m_amountsLayout->setContentsMargins(0, 0, 0, 0);
+    m_amountsLayout->setSpacing(4);
+    m_outerLayout->addWidget(m_amountsRow);
+
+    hide();
+}
+
+void RecipeLineRow::setCardChrome(bool enabled)
+{
+    // Palette colors like the item chip's chrome (REQ-UI-SELECTION-CARD), not
+    // visuals.toml, which is for world rendering. The selector names this class alone, so
+    // nothing inside the card inherits the border.
+    setAttribute(Qt::WA_StyledBackground, enabled);
+    setStyleSheet(enabled
+        ? QStringLiteral("RecipeLineRow { border: 1px solid palette(mid); "
+                         "border-radius: 4px; }")
+        : QString());
+    m_outerLayout->setContentsMargins(enabled ? QMargins(6, 4, 6, 4)
+                                              : QMargins(0, 0, 0, 0));
+}
+
+void RecipeLineRow::setLine(const Spec& spec)
+{
+    if (spec.isEmpty())
+    {
+        // Forgotten as well as hidden, so re-selecting the same recipe later is seen as
+        // a change and shows the row again.
+        m_spec = Spec();
+        hide();
+        return;
+    }
+    if (spec == m_spec)
+    {
+        return;
+    }
+
+    m_spec = spec;
+    rebuild(spec);
+    show();
+}
+
+void RecipeLineRow::rebuild(const Spec& spec)
+{
+    clearRow(m_headerLayout);
+    clearRow(m_amountsLayout);
+
+    // First line: which building runs the recipe and which recipe it is, where the line
+    // has to distinguish one producer from another (REQ-UI-ITEM-TOOLTIP). A building with
+    // no chip file leaves the icon off, as everywhere else (REQ-UI-BUILD-ICON).
+    if (spec.building.has_value() && m_buildingIcons != nullptr)
+    {
+        const QPixmap chip =
+            m_buildingIcons->getChip(buildingTypeId(*spec.building), kIconSizePx);
+        if (!chip.isNull())
+        {
+            QLabel* chipLabel = new QLabel(m_headerRow);
+            chipLabel->setPixmap(chip);
+            addAndShow(m_headerLayout, chipLabel);
+        }
+    }
+    if (!spec.name.isEmpty())
+    {
+        QLabel* nameLabel = new QLabel(spec.name, m_headerRow);
+        QFont nameFont = nameLabel->font();
+        nameFont.setBold(true);
+        nameLabel->setFont(nameFont);
+        addAndShow(m_headerLayout, nameLabel);
+    }
+    const bool hasHeader = m_headerLayout->count() > 0;
+    if (hasHeader)
+    {
+        m_headerLayout->addStretch(1);
+    }
+    m_headerRow->setVisible(hasHeader);
+
+    // Second line: what the cycle costs, makes and takes.
+    addAmounts(spec.inputs);
+    if (!spec.inputs.empty() && !spec.outputGroups.empty())
+    {
+        const QChar rightArrow(0x2192);  // U+2192 RIGHTWARDS ARROW
+        addAndShow(m_amountsLayout, new QLabel(QString(rightArrow), m_amountsRow));
+    }
+    for (std::size_t i = 0; i < spec.outputGroups.size(); ++i)
+    {
+        // Between one group and the next, so alternatives read as a choice rather than as
+        // one combined yield -- which is what a run of `+` would say (REQ-UI-RECIPE-SUMMARY).
+        if (i > 0)
+        {
+            addAndShow(m_amountsLayout, new QLabel(QStringLiteral("/"), m_amountsRow));
+        }
+        addAmounts(spec.outputGroups[i]);
+    }
+
+    if (spec.durationSeconds.has_value() && *spec.durationSeconds > 0.0)
+    {
+        const QChar middleDot(0x00B7);  // U+00B7 MIDDLE DOT
+        const QString time = spec.durationIsAddition
+            ? tr("+%1 s").arg(*spec.durationSeconds, 0, 'f', 1)
+            : tr("%1 s").arg(*spec.durationSeconds, 0, 'f', 1);
+        addAndShow(m_amountsLayout, new QLabel(
+            QStringLiteral("%1 %2").arg(middleDot).arg(time), m_amountsRow));
+    }
+    m_amountsLayout->addStretch(1);
+}
+
+void RecipeLineRow::addAmounts(const std::vector<Amount>& amounts)
+{
+    for (const Amount& entry : amounts)
+    {
+        // Between one item and the next, so a run of icons and numbers reads as a sum
+        // rather than as a list.
+        if (&entry != &amounts.front())
+        {
+            addAndShow(m_amountsLayout, new QLabel(QStringLiteral("+"), m_amountsRow));
+        }
+
+        // The item's icon on its colored square (REQ-UI-ITEM-ICON). A missing icon file
+        // is not an error: the square stands alone then, and only an item with no square
+        // either falls back to its id in text.
+        const QPixmap icon = (m_itemIcons != nullptr)
+            ? m_itemIcons->getSquarePixmap(entry.itemId, kIconSizePx)
+            : QPixmap();
+        if (!icon.isNull())
+        {
+            QLabel* iconLabel = new QLabel(m_amountsRow);
+            iconLabel->setPixmap(icon);
+            addAndShow(m_amountsLayout, iconLabel);
+        }
+        else
+        {
+            addAndShow(m_amountsLayout,
+                       new QLabel(QString::fromStdString(entry.itemId), m_amountsRow));
+        }
+        addAndShow(m_amountsLayout,
+                   new QLabel(QString::number(entry.amount), m_amountsRow));
+    }
+}

src/ui/RecipeLineRow.h

@@ -0,0 +1,124 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <vector>
+
+#include <QString>
+#include <QWidget>
+
+#include "BuildingType.h"
+#include "RecipesConfig.h"
+
+class BuildingIconCache;
+class ItemIconCache;
+class QHBoxLayout;
+class QVBoxLayout;
+
+// One recipe drawn: what it consumes, an arrow, what it produces, and how long a cycle
+// takes (REQ-UI-RECIPE-SUMMARY), under a header naming the building that runs it and the
+// recipe itself where the recipe has to identify itself. Every place the UI states what
+// something makes draws this same line, so a recipe reads alike wherever it is shown:
+//
+//  * beneath the selection button, for the recipe a building is running
+//    (REQ-UI-RECIPE-SUMMARY);
+//  * on a selection dialog's option buttons, under the option's name
+//    (REQ-UI-SELECT-OPTIONS);
+//  * in an item's production tooltip and in the unlock-choice dialog, there led by the
+//    icon of the building that runs the recipe and its name
+//    (REQ-UI-ITEM-TOOLTIP, REQ-DEF-SCHEMATIC-DROP);
+//  * on a module button and in the layout dialog's build cost, where there is a price
+//    and a time but nothing produced (REQ-MOD-UI-DIALOG, REQ-MOD-UI-STATS-PANEL).
+class RecipeLineRow : public QWidget
+{
+    Q_OBJECT
+
+public:
+    // One item and how many of it the line states.
+    struct Amount
+    {
+        std::string itemId;
+        int         amount = 0;
+
+        bool operator==(const Amount& other) const
+        {
+            return itemId == other.itemId && amount == other.amount;
+        }
+    };
+
+    // What the line says. Everything but the inputs is optional, which is what lets the
+    // one widget serve the summary, the option buttons, the tooltip lines and the cost
+    // lines.
+    struct Spec
+    {
+        // The chip of the building running the recipe, on the header line, where the
+        // recipe has to say which building that is -- an item may have several producers
+        // (REQ-UI-ITEM-TOOLTIP). Unset wherever the surrounding widget already
+        // establishes the building, and the header line is then left out entirely.
+        std::optional<BuildingType> building;
+        // The recipe's name, beside the building chip on the header line. Empty where the
+        // name is the caption of the widget around this one instead.
+        QString                     name;
+        std::vector<Amount>         inputs;
+        // What the recipe produces, one entry per output group (REQ-MAT-OUTPUT-GROUP).
+        // The items of a group are drawn joined by `+` because they come together, and the
+        // groups joined by `/` because only one of them happens. Empty for a line that
+        // produces no item of its own: a ship schematic, or a module's price. No arrow is
+        // drawn then.
+        std::vector<std::vector<Amount>> outputGroups;
+        std::optional<double>       durationSeconds;
+        // True where the time is added to something else rather than being a cycle of
+        // its own, and so reads "+3.0 s" (REQ-MOD-UI-DIALOG).
+        bool                        durationIsAddition = false;
+
+        bool operator==(const Spec& other) const
+        {
+            return building == other.building && name == other.name
+                && inputs == other.inputs && outputGroups == other.outputGroups
+                && durationSeconds == other.durationSeconds
+                && durationIsAddition == other.durationIsAddition;
+        }
+
+        bool isEmpty() const { return inputs.empty() && outputGroups.empty(); }
+    };
+
+    // A recipe's output groups as this row states them (REQ-MAT-OUTPUT-GROUP). Shared, so
+    // that every place drawing a recipe -- the summary, the option buttons, the tooltip
+    // lines -- converts it the same way rather than each keeping its own copy.
+    static std::vector<std::vector<Amount>> toOutputGroups(const RecipeDef& recipe);
+
+    // Both caches may be null, which leaves the icons off: an item with no square and
+    // no icon falls back to its id, and a building with no chip to its name alone.
+    // Neither is owned.
+    RecipeLineRow(ItemIconCache* itemIcons, BuildingIconCache* buildingIcons,
+                  QWidget* parent = nullptr);
+
+    // Hides the row when the spec has nothing to state, which is how a building with no
+    // recipe shows no summary at all (REQ-UI-RECIPE-SUMMARY).
+    void setLine(const Spec& spec);
+
+    // Boxes the line in a card of its own, for the two places that stack several of them
+    // (REQ-UI-ITEM-TOOLTIP, REQ-DEF-SCHEMATIC-DROP): a run of bare lines reads as one
+    // field of icons and numbers, and the box is what separates one recipe from the next.
+    // Off by default -- a line drawn inside a button or a panel section is already framed
+    // by what holds it.
+    void setCardChrome(bool enabled);
+
+private:
+    void rebuild(const Spec& spec);
+    void addAmounts(const std::vector<Amount>& amounts);
+
+    ItemIconCache*     m_itemIcons;
+    BuildingIconCache* m_buildingIcons;
+    QVBoxLayout*       m_outerLayout;
+    // The two lines, each a row widget of its own so a rebuild only has to empty their
+    // layouts -- no nested layout to take apart. The header is hidden where the spec
+    // names neither a building nor a recipe.
+    QWidget*           m_headerRow;
+    QHBoxLayout*       m_headerLayout;
+    QWidget*           m_amountsRow;
+    QHBoxLayout*       m_amountsLayout;
+    // What the row currently shows, so a refresh at tick rate rebuilds it only when the
+    // recipe actually changed.
+    Spec               m_spec;
+};

src/ui/RecipeSelectionDialog.cpp

@@ -2,61 +2,38 @@
 
 #include <cstddef>
 
-#include <QGridLayout>
-#include <QIcon>
-#include <QPixmap>
+#include <QFont>
+#include <QFrame>
+#include <QLabel>
 #include <QPushButton>
-#include <QSize>
-#include <QStringList>
+#include <QScrollArea>
 #include <QVBoxLayout>
 
 #include "Building.h"
 #include "BuildingType.h"
+#include "DialogDismiss.h"
 #include "DisplayName.h"
 #include "GameConfig.h"
-#include "ItemIconCache.h"
+#include "OptionButton.h"
 #include "RecipesConfig.h"
-#include "RecipeTooltip.h"
 #include "ShipsConfig.h"
 #include "Simulation.h"
 
 namespace
 {
 
-QString itemLine(const std::string& itemId, int amount)
+std::vector<RecipeLineRow::Amount> toAmounts(
+    const std::vector<RecipeIngredient>& ingredients)
 {
-    return QStringLiteral("  ")
-        + QString::fromStdString(toDisplayName(itemId))
-        + QStringLiteral(" x ") + QString::number(amount);
+    std::vector<RecipeLineRow::Amount> amounts;
+    amounts.reserve(ingredients.size());
+    for (const RecipeIngredient& ingredient : ingredients)
+    {
+        amounts.push_back(RecipeLineRow::Amount{ ingredient.item, ingredient.amount });
+    }
+    return amounts;
 }
 
-QString shipTooltip(const ShipDef& def)
-{
-    const QString name = QString::fromStdString(toDisplayName(def.id));
-
-    QStringList lines;
-    lines << QObject::tr("Ship: %1").arg(name);
-
-    if (def.schematic.materials.empty())
-    {
-        lines << QObject::tr("Materials: none");
-    }
-    else
-    {
-        lines << QObject::tr("Materials:");
-        for (const RecipeIngredient& material : def.schematic.materials)
-        {
-            lines << itemLine(material.item, material.amount);
-        }
-        lines << QObject::tr("  + installed modules");
-    }
-
-    lines << QObject::tr("Completion time: %1 s")
-        .arg(def.schematic.productionTimeSeconds);
-    lines << QObject::tr("Produces: 1 %1").arg(name);
-
-    return lines.join('\n');
-}
 
 }  // namespace
 
@@ -64,16 +41,30 @@ std::vector<RecipeSelectionOption> buildRecipeSelectionOptions(
     BuildingType type, Simulation& sim, const GameConfig& config)
 {
     std::vector<RecipeSelectionOption> options;
-    options.push_back({std::string(), QObject::tr("(None)"), QString()});
+    // The clearing option. On a building that picks its own recipe it does not leave the
+    // building idle but hands it back to that selection, and says so
+    // (REQ-UI-SELECT-OPTIONS, REQ-BLD-AUTO-RECIPE).
+    options.push_back({std::string(),
+                       isAutoRecipeBuildingType(type) ? QObject::tr("(Auto)")
+                                                      : QObject::tr("(None)"),
+                       RecipeLineRow::Spec()});
 
     if (type == BuildingType::Shipyard)
     {
         for (const ShipDef& def : config.ships.ships)
         {
             if (!sim.isSchematicUnlocked(def.id)) { continue; }
+
+            // The base materials and base production time, excluding the modules the
+            // player has not placed yet (REQ-UI-SELECT-OPTIONS). No output item: a ship
+            // has no icon, so the caption is what the option produces.
+            RecipeLineRow::Spec line;
+            line.inputs          = toAmounts(def.schematic.materials);
+            line.durationSeconds = def.schematic.productionTimeSeconds;
+
             options.push_back({def.id,
                                QString::fromStdString(toDisplayName(def.id)),
-                               shipTooltip(def)});
+                               line});
         }
     }
     else
@@ -87,16 +78,15 @@ std::vector<RecipeSelectionOption> buildRecipeSelectionOptions(
             {
                 continue;
             }
-            // Icon shown on the option button (REQ-UI-RECIPE-ICON): the recipe's
-            // configured icon item, else its first output item.
-            const std::string iconItemId = recipe.icon
-                ? *recipe.icon
-                : (recipe.outputs.empty() ? std::string()
-                                          : recipe.outputs.front().item);
+
+            RecipeLineRow::Spec line;
+            line.inputs          = toAmounts(recipe.inputs);
+            line.outputGroups    = RecipeLineRow::toOutputGroups(recipe);
+            line.durationSeconds = recipe.durationSeconds;
+
             options.push_back({recipe.id,
                                QString::fromStdString(toDisplayName(recipe.id)),
-                               buildRecipeTooltip(recipe),
-                               iconItemId});
+                               line});
         }
     }
 
@@ -105,46 +95,77 @@ std::vector<RecipeSelectionOption> buildRecipeSelectionOptions(
 
 namespace
 {
-    // On-screen size of a recipe option button's item icon (REQ-UI-RECIPE-ICON).
-    const QSize kOptionIconSize(32, 32);
+    // Height the option list is allowed to take, as the dialog's parent window's height
+    // less what the window margins and the dialog's own frame need. Fully unlocked, an
+    // Assembler offers more options than any window can hold, and the modal is never
+    // resized to fit (REQ-UI-PANEL-MODAL) -- so the list scrolls instead.
+    const int kListHeightReservePx = 80;
+
+    // Fallback cap for a dialog built without a parent window to measure.
+    const int kFallbackListHeightPx = 600;
 }
 
 RecipeSelectionDialog::RecipeSelectionDialog(
     const std::vector<RecipeSelectionOption>& options,
-    const QString& title, ItemIconCache* itemIcons, QWidget* parent)
+    const QString& title, ItemIconCache* itemIcons, BuildingIconCache* buildingIcons,
+    QWidget* parent)
     : QDialog(parent)
 {
     setWindowTitle(title);
     setModal(true);
 
     QVBoxLayout* mainLayout = new QVBoxLayout(this);
-    QGridLayout* grid = new QGridLayout();
-    mainLayout->addLayout(grid);
 
-    const int columnCount = 2;
+    // One vertical column of buttons, each stating what it makes (REQ-UI-SELECT-OPTIONS).
+    QScrollArea* scrollArea = new QScrollArea(this);
+    scrollArea->setWidgetResizable(true);
+    scrollArea->setFrameShape(QFrame::NoFrame);
+    scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    scrollArea->setSizeAdjustPolicy(QAbstractScrollArea::AdjustToContents);
+    scrollArea->setMaximumHeight(parent != nullptr
+        ? qMax(kListHeightReservePx, parent->height() - kListHeightReservePx)
+        : kFallbackListHeightPx);
+    mainLayout->addWidget(scrollArea);
+
+    QWidget*     list       = new QWidget(scrollArea);
+    QVBoxLayout* listLayout = new QVBoxLayout(list);
+    listLayout->setContentsMargins(0, 0, 0, 0);
+    listLayout->setSpacing(4);
+
     for (int i = 0; i < static_cast<int>(options.size()); ++i)
     {
         const RecipeSelectionOption& option = options[static_cast<std::size_t>(i)];
 
-        QPushButton* button = new QPushButton(this);
-        // Icon-only when the produced item has an icon (REQ-UI-RECIPE-ICON); otherwise
-        // fall back to the caption. The name stays reachable via the tooltip.
-        if (!option.iconItemId.empty() && itemIcons->hasIcon(option.iconItemId))
+        // An OptionButton so the face of widgets below is what sizes the button
+        // (REQ-UI-SELECT-OPTIONS).
+        OptionButton* button = new OptionButton(list);
+        if (option.line.isEmpty())
         {
-            button->setIcon(QIcon(itemIcons->getPixmap(
-                option.iconItemId, kOptionIconSize.width())));
-            button->setIconSize(kOptionIconSize);
+            // The "(None)" option makes nothing and is a caption alone
+            // (REQ-UI-SELECT-OPTIONS).
+            button->setText(option.caption);
         }
         else
         {
-            button->setText(option.caption);
+            // The name over the recipe it stands for. Both are transparent to the mouse
+            // so a click anywhere on the face still reaches the button beneath them.
+            QVBoxLayout* face = new QVBoxLayout(button);
+            face->setContentsMargins(8, 6, 8, 6);
+            face->setSpacing(2);
+
+            QLabel* nameLabel = new QLabel(option.caption, button);
+            QFont nameFont = nameLabel->font();
+            nameFont.setBold(true);
+            nameLabel->setFont(nameFont);
+            nameLabel->setAttribute(Qt::WA_TransparentForMouseEvents, true);
+            face->addWidget(nameLabel);
+
+            RecipeLineRow* line = new RecipeLineRow(itemIcons, buildingIcons, button);
+            line->setAttribute(Qt::WA_TransparentForMouseEvents, true);
+            face->addWidget(line);
+            line->setLine(option.line);
         }
-        if (!option.tooltip.isEmpty())
-        {
-            button->setToolTip(option.tooltip);
-        }
-        button->setMinimumHeight(40);
-        grid->addWidget(button, i / columnCount, i % columnCount);
+        listLayout->addWidget(button);
 
         m_optionIds.push_back(option.id);
         const int index = i;
@@ -153,6 +174,9 @@ RecipeSelectionDialog::RecipeSelectionDialog(
             onOptionClicked(index);
         });
     }
+    listLayout->addStretch(1);
+
+    scrollArea->setWidget(list);
 }
 
 std::optional<std::string> RecipeSelectionDialog::getChosenId() const
@@ -160,6 +184,18 @@ std::optional<std::string> RecipeSelectionDialog::getChosenId() const
     return m_chosenId;
 }
 
+void RecipeSelectionDialog::keyPressEvent(QKeyEvent* event)
+{
+    // Q dismisses, leaving the recipe as it was -- the same nothing that Escape and the
+    // close button do, since no option was clicked (REQ-UI-DIALOG-DISMISS).
+    if (isDialogDismissKey(*event))
+    {
+        reject();
+        return;
+    }
+    QDialog::keyPressEvent(event);
+}
+
 void RecipeSelectionDialog::onOptionClicked(int index)
 {
     if (index >= 0 && index < static_cast<int>(m_optionIds.size()))

src/ui/RecipeSelectionDialog.h

@@ -8,11 +8,13 @@
 #include <QString>
 
 #include "BuildingType.h"
+#include "RecipeLineRow.h"
 
 struct GameConfig;
+class BuildingIconCache;
+class ItemIconCache;
 class Simulation;
 class QPushButton;
-class ItemIconCache;
 
 // One selectable entry in the recipe/schematic selection dialog
 // (REQ-UI-SELECT-BUTTON). The "(None)" entry uses an empty id.
@@ -20,39 +22,40 @@ struct RecipeSelectionOption
 {
     std::string id;
     QString     caption;
-    QString     tooltip;
-    // Id of the item whose icon is shown on the option button (REQ-UI-RECIPE-ICON);
-    // empty for the "(None)" option and for Shipyard schematics, which keep their
-    // caption. When set but no icon file exists, the button falls back to the caption.
-    std::string iconItemId;
+    // What the option makes, drawn beneath its caption on the button
+    // (REQ-UI-SELECT-OPTIONS). Empty for the "(None)" option, which is a caption alone.
+    // A ship schematic fills the inputs and the time and leaves the outputs empty: a
+    // ship is not an item and has no icon, so the caption is what it produces.
+    RecipeLineRow::Spec line;
 };
 
 // Builds the lock-aware list of selectable options for a production building
-// of the given type, with display captions and info tooltips
-// (REQ-UI-SELECT-BUTTON, REQ-UI-SELECT-TOOLTIP). The first entry is always a
+// of the given type, with display captions and recipe lines
+// (REQ-UI-SELECT-BUTTON, REQ-UI-SELECT-OPTIONS). The first entry is always a
 // "(None)" option with an empty id. Shared by the selection dialog and the
-// panel selection button so both render identical captions and tooltips, and
+// panel selection button so both render identical captions, and
 // usable for construction sites which have no Building yet (REQ-BLD-SITE-CONFIG).
 std::vector<RecipeSelectionOption> buildRecipeSelectionOptions(
     BuildingType type, Simulation& sim, const GameConfig& config);
 
-// Modal dialog showing a grid of option buttons (REQ-UI-SELECT-BUTTON). The
+// Modal dialog listing the options in one vertical column (REQ-UI-SELECT-OPTIONS). The
 // game is paused by the caller while it is open. Clicking an option selects it
-// and closes the dialog; dismissing it (close/Esc) leaves no choice.
+// and closes the dialog; dismissing it (close/Esc/Q) leaves no choice.
 class RecipeSelectionDialog : public QDialog
 {
     Q_OBJECT
 
 public:
-    // itemIcons is the window-wide per-item icon cache (REQ-UI-ITEM-ICON); used to
-    // render recipe options icon-only (REQ-UI-RECIPE-ICON). Options whose item has
-    // no icon file fall back to their caption text. Not owned.
+    // The icon caches draw each option's recipe line (REQ-UI-ITEM-ICON). Not owned.
     RecipeSelectionDialog(const std::vector<RecipeSelectionOption>& options,
                           const QString& title, ItemIconCache* itemIcons,
-                          QWidget* parent = nullptr);
+                          BuildingIconCache* buildingIcons, QWidget* parent = nullptr);
 
     std::optional<std::string> getChosenId() const;
 
+protected:
+    void keyPressEvent(QKeyEvent* event) override;
+
 private:
     void onOptionClicked(int index);
 

src/ui/RecipeTooltip.cpp

@@ -1,52 +0,0 @@
-#include "RecipeTooltip.h"
-
-#include <QObject>
-#include <QStringList>
-
-#include "DisplayName.h"
-#include "RecipesConfig.h"
-
-namespace
-{
-
-QString itemLine(const std::string& itemId, int amount)
-{
-    return QStringLiteral("  ")
-        + QString::fromStdString(toDisplayName(itemId))
-        + QStringLiteral(" x ") + QString::number(amount);
-}
-
-}  // namespace
-
-QString buildRecipeTooltip(const RecipeDef& recipe)
-{
-    QStringList lines;
-    lines << QObject::tr("Recipe: %1")
-        .arg(QString::fromStdString(toDisplayName(recipe.id)));
-
-    if (recipe.inputs.empty())
-    {
-        lines << QObject::tr("Inputs: none");
-    }
-    else
-    {
-        lines << QObject::tr("Inputs:");
-        for (const RecipeIngredient& ingredient : recipe.inputs)
-        {
-            lines << itemLine(ingredient.item, ingredient.amount);
-        }
-    }
-
-    lines << QObject::tr("Completion time: %1 s").arg(recipe.durationSeconds);
-
-    if (!recipe.outputs.empty())
-    {
-        lines << QObject::tr("Produces:");
-        for (const RecipeOutput& output : recipe.outputs)
-        {
-            lines << itemLine(output.item, output.amount);
-        }
-    }
-
-    return lines.join('\n');
-}

src/ui/RecipeTooltip.h

@@ -1,11 +0,0 @@
-#pragma once
-
-#include <QString>
-
-struct RecipeDef;
-
-// Builds the recipe info tooltip text (REQ-UI-SELECT-TOOLTIP): the recipe name,
-// each input item name and quantity, the completion time, and the produced
-// output item name and quantity. Shared by the recipe-selection dialog and the
-// schematic choice dialog's "Unlocks recipes:" list so both render identically.
-QString buildRecipeTooltip(const RecipeDef& recipe);

src/ui/SchematicChoiceDialog.cpp

@@ -6,12 +6,25 @@
 #include <QVBoxLayout>
 
 #include "DisplayName.h"
-#include "RecipeTooltip.h"
+#include "RecipeLineRow.h"
 #include "RecipesConfig.h"
 
 namespace
 {
 
+std::vector<RecipeLineRow::Amount> toAmounts(
+    const std::vector<RecipeIngredient>& ingredients)
+{
+    std::vector<RecipeLineRow::Amount> amounts;
+    amounts.reserve(ingredients.size());
+    for (const RecipeIngredient& ingredient : ingredients)
+    {
+        amounts.push_back(RecipeLineRow::Amount{ ingredient.item, ingredient.amount });
+    }
+    return amounts;
+}
+
+
 QString grantKindLabel(SchematicType type)
 {
     switch (type)
@@ -28,7 +41,8 @@ QString grantKindLabel(SchematicType type)
 
 SchematicChoiceDialog::SchematicChoiceDialog(
     const std::vector<SchematicChoiceOption>& options,
-    const RecipesConfig& recipes,
+    const RecipesConfig& recipes, ItemIconCache* itemIcons,
+    BuildingIconCache* buildingIcons,
     QWidget* parent)
     : QDialog(parent)
     , m_chosenIndex(0)
@@ -56,7 +70,12 @@ SchematicChoiceDialog::SchematicChoiceDialog(
 
         QWidget* card = new QWidget(this);
         QVBoxLayout* cardLayout = new QVBoxLayout(card);
-        card->setStyleSheet("QWidget { border: 1px solid gray; padding: 8px; }");
+        // Scoped to the card by object name. An unscoped "QWidget" selector cascades to
+        // every descendant, which boxed each label and each icon of the recipe lines
+        // inside it as well.
+        card->setObjectName(QStringLiteral("schematicChoiceCard"));
+        card->setStyleSheet(QStringLiteral(
+            "QWidget#schematicChoiceCard { border: 1px solid gray; padding: 8px; }"));
 
         QLabel* nameLabel = new QLabel(QString::fromStdString(option.displayName), card);
         QFont nameFont = nameLabel->font();
@@ -108,14 +127,24 @@ SchematicChoiceDialog::SchematicChoiceDialog(
             {
                 for (const std::string& recipeId : option.newlyUnlockedRecipeIds)
                 {
-                    QLabel* recipeLabel = new QLabel(
-                        QString::fromStdString(toDisplayName(recipeId)), card);
-                    recipeLabel->setAlignment(Qt::AlignCenter);
-                    if (const RecipeDef* def = recipes.findRecipeDef(recipeId))
-                    {
-                        recipeLabel->setToolTip(buildRecipeTooltip(*def));
-                    }
-                    cardLayout->addWidget(recipeLabel);
+                    const RecipeDef* def = recipes.findRecipeDef(recipeId);
+                    if (def == nullptr) { continue; }
+
+                    // The recipe drawn as it is everywhere else, led by the building
+                    // that runs it and its name, so the line says everything there is
+                    // to say about it and carries no tooltip (REQ-DEF-SCHEMATIC-DROP).
+                    RecipeLineRow::Spec spec;
+                    spec.building        = def->building;
+                    spec.name            = QString::fromStdString(toDisplayName(def->id));
+                    spec.inputs          = toAmounts(def->inputs);
+                    spec.outputGroups    = RecipeLineRow::toOutputGroups(*def);
+                    spec.durationSeconds = def->durationSeconds;
+
+                    RecipeLineRow* line =
+                        new RecipeLineRow(itemIcons, buildingIcons, card);
+                    line->setCardChrome(true);
+                    cardLayout->addWidget(line);
+                    line->setLine(spec);
                 }
             }
         }
@@ -138,6 +167,12 @@ int SchematicChoiceDialog::getChosenIndex() const
     return m_chosenIndex;
 }
 
+void SchematicChoiceDialog::reject()
+{
+    // Deliberately empty: the dialog stays open until an option is clicked
+    // (REQ-DEF-SCHEMATIC-DROP). The game is paused meanwhile, so nothing waits on it.
+}
+
 void SchematicChoiceDialog::onOptionClicked(int index)
 {
     m_chosenIndex = index;

src/ui/SchematicChoiceDialog.h

@@ -7,18 +7,34 @@
 #include "SchematicChoiceOption.h"
 
 struct RecipesConfig;
+class BuildingIconCache;
+class ItemIconCache;
 
+// The drop's choice dialog (REQ-DEF-SCHEMATIC-DROP). Unlike every other dialog it
+// cannot be dismissed: clicking an option is the only way out, so getChosenIndex()
+// always names an option the player picked, and exec() only ever returns Accepted.
 class SchematicChoiceDialog : public QDialog
 {
     Q_OBJECT
 
 public:
+    // The icon caches draw the recipe lines of the "Unlocks recipes" list
+    // (REQ-DEF-SCHEMATIC-DROP, REQ-UI-ITEM-ICON, REQ-UI-BUILD-ICON). Not owned.
     SchematicChoiceDialog(const std::vector<SchematicChoiceOption>& options,
-                          const RecipesConfig& recipes,
+                          const RecipesConfig& recipes, ItemIconCache* itemIcons,
+                          BuildingIconCache* buildingIcons,
                           QWidget* parent = nullptr);
 
     int getChosenIndex() const;
 
+public slots:
+    // Refuses the dismissal (REQ-DEF-SCHEMATIC-DROP): the drop is a reward the player
+    // has earned, and leaving without choosing would either forfeit it or award the
+    // option that happens to be first. Escape, Alt+F4, and the window manager's close
+    // all funnel through QDialog::reject(), so declining it here turns away every one of
+    // them at once rather than swallowing keys one at a time.
+    void reject() override;
+
 private:
     void onOptionClicked(int index);
 

src/ui/SelectedBuildingPanel.cpp

@@ -1,858 +0,0 @@
-#include "SelectedBuildingPanel.h"
-#include "FactoryQueries.h"
-
-#include <algorithm>
-#include <cctype>
-#include <map>
-#include <set>
-#include <string>
-
-#include <QLabel>
-#include <QListWidget>
-#include <QPushButton>
-#include <QVBoxLayout>
-
-#include "BeltSystem.h"
-#include "Command.h"
-#include "CommandRequestedEvent.h"
-#include "EntitySelectionChangedEvent.h"
-#include "EventManager.h"
-#include "FieldSelectionPanel.h"
-#include "TickAdvancedEvent.h"
-#include "Building.h"
-#include "BuildingSystem.h"
-#include "BuildingType.h"
-#include "ItemType.h"
-#include "LayoutDialogRequestedEvent.h"
-#include "ModulesConfig.h"
-#include "PlayerCommandsAppliedEvent.h"
-#include "RecipeSelectionDialog.h"
-#include "RecipeSelectionRequestedEvent.h"
-#include "Rotation.h"
-#include "ShipLayoutPreview.h"
-#include "Simulation.h"
-
-namespace
-{
-
-QString buildingTypeName(BuildingType type)
-{
-    if (type == BuildingType::Hq)
-    {
-        return QObject::tr("Player HQ");
-    }
-
-    const std::string id = buildingTypeId(type);
-    QString result;
-    bool nextUpper = true;
-    for (char c : id)
-    {
-        if (c == '_')
-        {
-            result += ' ';
-            nextUpper = true;
-        }
-        else if (nextUpper)
-        {
-            result += static_cast<char>(std::toupper(static_cast<unsigned char>(c)));
-            nextUpper = false;
-        }
-        else
-        {
-            result += c;
-        }
-    }
-    return result;
-}
-
-bool isProductionBuilding(BuildingType type)
-{
-    return type == BuildingType::Miner
-        || type == BuildingType::Smelter
-        || type == BuildingType::Assembler
-        || type == BuildingType::ReprocessingPlant
-        || type == BuildingType::Shipyard;
-}
-
-// Buildings that expose a player recipe/schematic selection control
-// (REQ-UI-SELECT-BUTTON): Miner ore type, Assembler recipe, Shipyard schematic.
-// The Smelter and Reprocessing Plant auto-process and offer no selection
-// (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
-bool hasRecipeSelection(BuildingType type)
-{
-    return type == BuildingType::Miner
-        || type == BuildingType::Assembler
-        || type == BuildingType::Shipyard;
-}
-
-QString rotationLabel(Rotation r)
-{
-    switch (r)
-    {
-        case Rotation::North: return QObject::tr("North (↑)");
-        case Rotation::East:  return QObject::tr("East (→)");
-        case Rotation::South: return QObject::tr("South (↓)");
-        case Rotation::West:  return QObject::tr("West (←)");
-    }
-    return "";
-}
-
-}  // namespace
-
-
-SelectedBuildingPanel::SelectedBuildingPanel(Simulation* sim,
-                                             const GameConfig* config,
-                                             QWidget* parent)
-    : QWidget(parent)
-    , m_sim(sim)
-    , m_config(config)
-    , m_splitterTile(0, 0)
-{
-    m_layout = new QVBoxLayout(this);
-    m_layout->setContentsMargins(8, 8, 8, 8);
-    m_layout->setSpacing(4);
-    m_layout->setAlignment(Qt::AlignTop);
-
-    m_titleLabel   = new QLabel(this);
-    m_recipeSelectButton = new QPushButton(this);
-    m_clearBeltBtn = new QPushButton(tr("Clear Items"), this);
-    m_filterALabel = new QLabel(this);
-    m_filterAList  = new QListWidget(this);
-    m_filterBLabel = new QLabel(this);
-    m_filterBList  = new QListWidget(this);
-    m_layoutPreview      = new ShipLayoutPreview(this);
-    m_configureLayoutBtn = new QPushButton(tr("Configure Layout"), this);
-    m_buffersLabel = new QLabel(this);
-    m_buffersLabel->setWordWrap(true);
-
-    m_filterAList->setMaximumHeight(100);
-    m_filterBList->setMaximumHeight(100);
-
-    m_layout->addWidget(m_titleLabel);
-    m_layout->addWidget(m_recipeSelectButton);
-    m_layout->addWidget(m_layoutPreview);
-    m_layout->addWidget(m_configureLayoutBtn);
-    m_layout->addWidget(m_clearBeltBtn);
-    m_layout->addWidget(m_filterALabel);
-    m_layout->addWidget(m_filterAList);
-    m_layout->addWidget(m_filterBLabel);
-    m_layout->addWidget(m_filterBList);
-    m_layout->addWidget(m_buffersLabel);
-
-    connect(m_recipeSelectButton, &QPushButton::clicked,
-            this, &SelectedBuildingPanel::onSelectRecipeClicked);
-    connect(m_clearBeltBtn, &QPushButton::clicked,
-            this, &SelectedBuildingPanel::onClearBelt);
-    connect(m_configureLayoutBtn, &QPushButton::clicked, this, [this]() {
-        if (m_singleBuildingId.has_value())
-        {
-            EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<LayoutDialogRequestedEvent>(*m_singleBuildingId));
-        }
-    });
-    connect(m_filterAList, &QListWidget::itemChanged,
-            this, &SelectedBuildingPanel::onSplitterFilterChanged);
-    connect(m_filterBList, &QListWidget::itemChanged,
-            this, &SelectedBuildingPanel::onSplitterFilterChanged);
-
-    // The field selection renders below the building content and hides itself while
-    // nothing field-side is selected, so it costs no space then.
-    m_fieldSelectionPanel = new FieldSelectionPanel(sim, config, this);
-    m_layout->addWidget(m_fieldSelectionPanel);
-
-    buildEmpty();
-
-    registerForEvents();
-}
-
-SelectedBuildingPanel::~SelectedBuildingPanel()
-{
-    unregisterForEvents();
-}
-
-void SelectedBuildingPanel::onSelectionChanged(const std::vector<BuildingId>& ids)
-{
-    m_selectedBuildingIds = ids;
-    if (!ids.empty())
-    {
-        // A building selection is exclusive: it supersedes any field selection —
-        // actors and scrap (REQ-UI-SELECTION-CATEGORIES).
-        m_fieldSelectionPanel->clearSelection();
-    }
-    rebuild();
-}
-
-void SelectedBuildingPanel::yieldToFieldSelection()
-{
-    // The mirror image of onSelectionChanged(): a field selection — actors, debris, or
-    // both — supersedes any building selection (REQ-UI-SELECTION-CATEGORIES). An empty
-    // field selection changes nothing here: the building content, if any, keeps the panel.
-    if (!m_fieldSelectionPanel->hasSelection()) { return; }
-    m_selectedBuildingIds.clear();
-    buildEmpty();
-}
-
-void SelectedBuildingPanel::rebuild()
-{
-    if (m_selectedBuildingIds.empty())
-    {
-        buildEmpty();
-    }
-    else if (m_selectedBuildingIds.size() == 1)
-    {
-        buildSingle(m_selectedBuildingIds[0]);
-    }
-    else
-    {
-        buildMulti(m_selectedBuildingIds);
-    }
-}
-
-void SelectedBuildingPanel::hideAllWidgets()
-{
-    m_titleLabel->hide();
-    m_recipeSelectButton->hide();
-    m_layoutPreview->hide();
-    m_configureLayoutBtn->hide();
-    m_clearBeltBtn->hide();
-    m_filterALabel->hide();
-    m_filterAList->hide();
-    m_filterBLabel->hide();
-    m_filterBList->hide();
-    m_buffersLabel->hide();
-}
-
-void SelectedBuildingPanel::buildEmpty()
-{
-    // Shows nothing for the building category — either because nothing is selected or
-    // because the field category has taken the panel over.
-    m_singleBuildingId = std::nullopt;
-    hideAllWidgets();
-}
-
-void SelectedBuildingPanel::buildSingle(BuildingId id)
-{
-    m_singleBuildingId = id;
-    hideAllWidgets();
-
-    const Building*         b = findBuilding(m_sim->getFactoryState(), id);
-    const ConstructionSite* s = b ? nullptr : findSite(m_sim->getFactoryState(), id);
-    if (!b && !s)
-    {
-        buildEmpty();
-        return;
-    }
-    m_singleIsSite = (s != nullptr);
-
-    // A construction site exposes the same configuration as the operational
-    // building it will become (REQ-BLD-SITE-CONFIG). The only difference is
-    // that its buffer/production rows are replaced by a construction-progress
-    // line, since a site has no buffers and runs no production cycle.
-    const BuildingType type     = b ? b->type     : s->type;
-    const std::string& recipeId = b ? b->recipeId : s->recipeId;
-    const std::optional<ShipLayoutConfig>& shipLayout =
-        b ? b->shipLayout : s->shipLayout;
-    const QPoint anchor = b ? b->anchor : s->anchor;
-
-    m_titleLabel->setText(m_singleIsSite
-        ? tr("(Building) %1").arg(buildingTypeName(type))
-        : buildingTypeName(type));
-    m_titleLabel->show();
-    m_buffersLabel->show();
-
-    if (hasRecipeSelection(type))
-    {
-        const std::vector<RecipeSelectionOption> options =
-            buildRecipeSelectionOptions(type, *m_sim, *m_config);
-
-        const RecipeSelectionOption* current = nullptr;
-        for (const RecipeSelectionOption& option : options)
-        {
-            if (option.id == recipeId)
-            {
-                current = &option;
-                break;
-            }
-        }
-
-        if (current && !current->id.empty())
-        {
-            m_recipeSelectButton->setText(current->caption);
-            m_recipeSelectButton->setToolTip(current->tooltip);
-        }
-        else
-        {
-            const QString placeholder = (type == BuildingType::Shipyard)
-                ? tr("Select schematic")
-                : tr("Select recipe");
-            m_recipeSelectButton->setText(placeholder);
-            m_recipeSelectButton->setToolTip(QString());
-        }
-        m_recipeSelectButton->show();
-
-        updateShipyardLayoutWidgets(type, recipeId, shipLayout);
-    }
-    else
-    {
-        m_recipeSelectButton->hide();
-        updateShipyardLayoutWidgets(type, recipeId, shipLayout);
-    }
-
-    // Belt "Clear" removes items from a live belt tile; a construction site has
-    // none and is not registered with BeltSystem yet, so hide it for sites.
-    if (isBeltSubsystemType(type) && !m_singleIsSite)
-    {
-        m_clearBeltBtn->show();
-    }
-    else
-    {
-        m_clearBeltBtn->hide();
-    }
-
-    if (type == BuildingType::Splitter)
-    {
-        std::optional<BeltSystem::SplitterInfo> info;
-        if (m_singleIsSite)
-        {
-            info = getSiteSplitterInfo(m_sim->getFactoryState(), m_sim->getConfig(), id);
-        }
-        else
-        {
-            m_splitterTile = anchor;
-            info = m_sim->getBelts().getSplitterInfo(m_splitterTile);
-        }
-        buildSplitterFilters(info);
-    }
-    else
-    {
-        m_filterALabel->hide();
-        m_filterAList->hide();
-        m_filterBLabel->hide();
-        m_filterBList->hide();
-    }
-
-    if (m_singleIsSite)
-    {
-        refreshSiteProgress(s);
-    }
-    else
-    {
-        refreshBuffers(b);
-    }
-}
-
-void SelectedBuildingPanel::refreshSiteProgress(const ConstructionSite* s)
-{
-    QString progress;
-    if (s->completesAt == 0)
-    {
-        progress = tr("Queued");
-    }
-    else
-    {
-        const BuildingDef* def = nullptr;
-        for (const BuildingDef& d : m_config->buildings.buildings)
-        {
-            if (d.type == s->type) { def = &d; break; }
-        }
-        if (def && def->constructionTimeSeconds > 0)
-        {
-            const Tick duration = secondsToTicks(def->constructionTimeSeconds);
-            const Tick elapsed  = m_sim->getCurrentTick() - (s->completesAt - duration);
-            const int pct = static_cast<int>(
-                std::max(Tick(0), std::min(duration, elapsed)) * 100 / duration);
-            progress = tr("%1% complete").arg(pct);
-        }
-        else
-        {
-            progress = tr("Building...");
-        }
-    }
-    m_buffersLabel->setText(progress);
-}
-
-void SelectedBuildingPanel::refreshBuffers(const Building* b)
-{
-    const RecipeDef* recipe  = findRecipe(b);
-    const ShipDef*   shipDef = (b->type == BuildingType::Shipyard)
-                                ? findShipDef(b->recipeId)
-                                : nullptr;
-
-    // Auto-recipe buildings (Smelter, Reprocessing Plant) have no selected
-    // recipe; while a cycle runs, resolve the recipe actually in production so
-    // the cycle time and progress can be shown (REQ-UI-PRODUCTION-PROGRESS).
-    if (!recipe && isAutoRecipeBuildingType(b->type) && b->production.has_value())
-    {
-        recipe = m_config->recipes.findRecipeDef(b->production->recipeId, b->type);
-    }
-
-    QString bufText;
-
-    if (!b->inputBuffer.counts.empty())
-    {
-        bufText += tr("Input: ");
-        for (const std::pair<const ItemType, int>& entry : b->inputBuffer.counts)
-        {
-            int perCycle = 0;
-            if (recipe)
-            {
-                for (const RecipeIngredient& ing : recipe->inputs)
-                {
-                    if (ing.item == entry.first.id) { perCycle = ing.amount; break; }
-                }
-            }
-            else if (shipDef)
-            {
-                for (const RecipeIngredient& mat : shipDef->schematic.materials)
-                {
-                    if (mat.item == entry.first.id) { perCycle = mat.amount; break; }
-                }
-                if (b->shipLayout.has_value())
-                {
-                    for (const PlacedModule& pm : b->shipLayout->placedModules)
-                    {
-                        const ModuleDef* modDef =
-                            m_config->modules.findModuleDef(pm.moduleId);
-                        if (!modDef) { continue; }
-                        for (const RecipeIngredient& ing : modDef->materials)
-                        {
-                            if (ing.item == entry.first.id)
-                            {
-                                perCycle += ing.amount;
-                            }
-                        }
-                    }
-                }
-            }
-            bufText += QString::fromStdString(entry.first.id)
-                + ": " + QString::number(entry.second);
-            if (perCycle > 0)
-            {
-                bufText += "/" + QString::number(perCycle);
-            }
-            bufText += "  ";
-        }
-        bufText += "\n";
-    }
-
-    // Count output-side items: buffered plus still-emerging on the output belts.
-    // An emerging item still belongs to the output buffer (REQ-MAT-OUTPUT-EMERGE),
-    // so it must be included here or it would vanish from the panel while animating.
-    std::map<std::string, int> outCounts;
-    for (const Item& item : b->outputBuffer.items)
-    {
-        outCounts[item.type.id]++;
-    }
-    for (const std::vector<BeltItemSlot>& lane : b->emergingItems)
-    {
-        for (const BeltItemSlot& slot : lane)
-        {
-            outCounts[slot.item.type.id]++;
-        }
-    }
-
-    if (recipe && !recipe->outputs.empty())
-    {
-        bufText += tr("Output: ");
-        for (const RecipeOutput& out : recipe->outputs)
-        {
-            const std::map<std::string, int>::const_iterator it =
-                outCounts.find(out.item);
-            const int count = (it != outCounts.end()) ? it->second : 0;
-            bufText += QString::fromStdString(out.item)
-                + ": " + QString::number(count)
-                + "/" + QString::number(out.amount) + "  ";
-        }
-    }
-    else if (!outCounts.empty())
-    {
-        bufText += tr("Output: ");
-        for (const std::pair<const std::string, int>& entry : outCounts)
-        {
-            bufText += QString::fromStdString(entry.first)
-                + ": " + QString::number(entry.second) + "  ";
-        }
-    }
-
-    if (isProductionBuilding(b->type)
-        && (recipe || shipDef || isAutoRecipeBuildingType(b->type)))
-    {
-        if (recipe || shipDef)
-        {
-            double durationSeconds = recipe
-                ? recipe->durationSeconds
-                : shipDef->schematic.productionTimeSeconds;
-
-            if (shipDef && b->shipLayout.has_value())
-            {
-                for (const PlacedModule& pm : b->shipLayout->placedModules)
-                {
-                    const ModuleDef* modDef =
-                        m_config->modules.findModuleDef(pm.moduleId);
-                    if (modDef)
-                    {
-                        durationSeconds += modDef->productionTimeSeconds;
-                    }
-                }
-            }
-
-            bufText += tr("Cycle: %1 s\n").arg(durationSeconds, 0, 'f', 1);
-
-            if (b->production.has_value())
-            {
-                const Tick cycleTicks  = secondsToTicks(durationSeconds);
-                const Tick completesAt = b->production->completesAt;
-                const Tick currentTick = m_sim->getCurrentTick();
-                const Tick elapsed     = currentTick - (completesAt - cycleTicks);
-                const int  pct         = static_cast<int>(
-                    std::max(Tick(0), std::min(cycleTicks, elapsed)) * 100 / cycleTicks);
-                bufText += tr("Progress: %1%\n").arg(pct);
-            }
-            else
-            {
-                bufText += tr("Progress: idle\n");
-            }
-        }
-        else
-        {
-            // Auto-recipe building with no active cycle: no single recipe to
-            // show a cycle time for.
-            bufText += tr("Progress: idle\n");
-        }
-    }
-
-    m_buffersLabel->setText(bufText);
-
-    // The recipe/schematic is applied via a queued command that only drains on a
-    // later frame, so the per-tick refresh must own the shipyard preview and the
-    // Configure Layout button's visibility; otherwise they stay hidden until the
-    // building is re-selected (which re-runs buildSingle).
-    updateShipyardLayoutWidgets(b->type, b->recipeId, b->shipLayout);
-}
-
-void SelectedBuildingPanel::updateShipyardLayoutWidgets(
-    BuildingType type,
-    const std::string& recipeId,
-    const std::optional<ShipLayoutConfig>& shipLayout)
-{
-    // The preview and Configure button are shipyard-only controls; hide them
-    // entirely for other building types.
-    if (type != BuildingType::Shipyard)
-    {
-        m_layoutPreview->hide();
-        m_configureLayoutBtn->hide();
-        return;
-    }
-
-    const ShipDef* shipDef = findShipDef(recipeId);
-    const bool hasSchematic = shipDef && !shipDef->layout.empty();
-
-    // Always show the preview and Configure button for a shipyard; they are only
-    // enabled once a schematic is selected (REQ-MOD-UI-PREVIEW).
-    if (hasSchematic)
-    {
-        ShipLayoutConfig layout;
-        if (shipLayout.has_value())
-        {
-            layout = *shipLayout;
-        }
-        m_layoutPreview->setShipAndLayout(
-            shipDef->layout, layout, &m_config->modules);
-    }
-    else
-    {
-        m_layoutPreview->showPlaceholder();
-    }
-
-    m_layoutPreview->setEnabled(hasSchematic);
-    m_configureLayoutBtn->setEnabled(hasSchematic);
-    m_layoutPreview->show();
-    m_configureLayoutBtn->show();
-}
-
-const RecipeDef* SelectedBuildingPanel::findRecipe(const Building* b) const
-{
-    if (b->recipeId.empty()) { return nullptr; }
-    return m_config->recipes.findRecipeDef(b->recipeId, b->type);
-}
-
-const ShipDef* SelectedBuildingPanel::findShipDef(const std::string& id) const
-{
-    if (id.empty()) { return nullptr; }
-    return m_config->ships.findShipDef(id);
-}
-
-void SelectedBuildingPanel::handleEvent(std::shared_ptr<const TickAdvancedEvent> /*event*/)
-{
-    refreshSelectionDisplay(RefreshReason::PeriodicTick);
-}
-
-void SelectedBuildingPanel::handleEvent(
-    std::shared_ptr<const PlayerCommandsAppliedEvent> /*event*/)
-{
-    // Player commands (e.g. choosing a shipyard schematic) are applied by a
-    // queued drain, not synchronously. When the game is paused no tick advances,
-    // so TickAdvancedEvent never fires; refresh here too, otherwise the panel
-    // would not reflect the change until the next tick or a re-selection.
-    refreshSelectionDisplay(RefreshReason::CommandApplied);
-}
-
-void SelectedBuildingPanel::refreshSelectionDisplay(RefreshReason reason)
-{
-    // Only a single selected building has live content to refresh. While the field
-    // category owns the panel there is none: yieldToFieldSelection() has cleared it, so
-    // this returns immediately and the field panel refreshes itself off the same events.
-    if (!m_singleBuildingId.has_value()) { return; }
-    const Building* b = findBuilding(m_sim->getFactoryState(), *m_singleBuildingId);
-    if (b)
-    {
-        if (m_titleLabel->text().startsWith(tr("(Building) ")))
-        {
-            rebuild();
-        }
-        else
-        {
-            refreshBuffers(b);
-        }
-        return;
-    }
-    const ConstructionSite* s = findSite(m_sim->getFactoryState(), *m_singleBuildingId);
-    if (s)
-    {
-        // A periodic tick only advances construction progress, so update just the
-        // progress label. Rebuilding every tick would hide/re-show all widgets and
-        // cancel any in-progress click on the recipe button. An applied command
-        // may have changed the site's recipe/layout, so rebuild in that case.
-        if (reason == RefreshReason::CommandApplied)
-        {
-            rebuild();
-        }
-        else
-        {
-            refreshSiteProgress(s);
-        }
-        return;
-    }
-    buildEmpty();
-}
-
-void SelectedBuildingPanel::buildMulti(const std::vector<BuildingId>& ids)
-{
-    m_singleBuildingId = std::nullopt;
-    m_recipeSelectButton->hide();
-    m_clearBeltBtn->hide();
-    m_filterALabel->hide();
-    m_filterAList->hide();
-    m_filterBLabel->hide();
-    m_filterBList->hide();
-    m_buffersLabel->hide();
-
-    std::map<BuildingType, int> counts;
-    for (BuildingId id : ids)
-    {
-        const Building* b = findBuilding(m_sim->getFactoryState(), id);
-        if (b)
-        {
-            counts[b->type]++;
-            continue;
-        }
-        const ConstructionSite* s = findSite(m_sim->getFactoryState(), id);
-        if (s)
-        {
-            counts[s->type]++;
-        }
-    }
-
-    bool hasBelt = false;
-    int totalCost = 0;
-    QString text;
-    for (const std::pair<const BuildingType, int>& entry : counts)
-    {
-        text += buildingTypeName(entry.first) + " x "
-            + QString::number(entry.second) + "\n";
-        if (isBeltSubsystemType(entry.first))
-        {
-            hasBelt = true;
-        }
-        // Total placement cost counts only player-placeable buildings; the HQ
-        // and defence stations are excluded (REQ-UI-MULTI-SELECTION).
-        const BuildingDef* def = m_config->buildings.findBuildingDef(entry.first);
-        if (def && def->playerPlaceable)
-        {
-            totalCost += def->cost * entry.second;
-        }
-    }
-    text += tr("Total: %1 Building Blocks").arg(totalCost);
-    m_titleLabel->setText(text.trimmed());
-    m_titleLabel->show();
-
-    if (hasBelt)
-    {
-        m_clearBeltBtn->show();
-    }
-}
-
-void SelectedBuildingPanel::onSelectRecipeClicked()
-{
-    if (!m_singleBuildingId.has_value())
-    {
-        return;
-    }
-    // The emit is synchronous: MainWindow pauses the game, runs the modal
-    // selection dialog, and restores the speed before this returns. The chosen
-    // recipe/schematic is only *enqueued* as a command, though, and drains on a
-    // later frame -- so this rebuild() still sees the old recipe. The per-tick
-    // refreshBuffers() path picks up the new schematic (and shows the layout
-    // preview + Configure Layout button) once the command has been applied.
-    EventManager::getInstance()->sendEventImmediately(
-        std::make_shared<RecipeSelectionRequestedEvent>(*m_singleBuildingId));
-    rebuild();
-}
-
-void SelectedBuildingPanel::buildSplitterFilters(
-    const std::optional<BeltSystem::SplitterInfo>& info)
-{
-    if (!info.has_value())
-    {
-        m_filterALabel->hide();
-        m_filterAList->hide();
-        m_filterBLabel->hide();
-        m_filterBList->hide();
-        return;
-    }
-
-    const std::vector<std::string> items = getAllItemIds();
-
-    auto populateList = [&](QListWidget* list, QLabel* label,
-                            const QString& dirLabel,
-                            const std::vector<ItemType>& filter)
-    {
-        label->setText(tr("%1 filter (empty = all):").arg(dirLabel));
-        list->blockSignals(true);
-        list->clear();
-        for (const std::string& itemId : items)
-        {
-            if (!m_sim->isItemUnlocked(itemId)) { continue; }
-            QListWidgetItem* row = new QListWidgetItem(
-                QString::fromStdString(itemId), list);
-            const bool checked = filter.empty()
-                ? false
-                : std::find(filter.begin(), filter.end(),
-                            ItemType{itemId}) != filter.end();
-            row->setCheckState(checked ? Qt::Checked : Qt::Unchecked);
-            row->setFlags(row->flags() | Qt::ItemIsUserCheckable);
-        }
-        list->blockSignals(false);
-        label->show();
-        list->show();
-    };
-
-    populateList(m_filterAList, m_filterALabel,
-                 rotationLabel(info->outputA), info->filterA);
-    populateList(m_filterBList, m_filterBLabel,
-                 rotationLabel(info->outputB), info->filterB);
-}
-
-void SelectedBuildingPanel::onSplitterFilterChanged()
-{
-    if (!m_singleBuildingId.has_value())
-    {
-        return;
-    }
-
-    auto collectFilter = [](QListWidget* list) -> std::vector<ItemType>
-    {
-        std::vector<ItemType> filter;
-        for (int i = 0; i < list->count(); ++i)
-        {
-            const QListWidgetItem* row = list->item(i);
-            if (row->checkState() == Qt::Checked)
-            {
-                filter.push_back(ItemType{row->text().toStdString()});
-            }
-        }
-        return filter;
-    };
-
-    if (m_singleIsSite)
-    {
-        std::shared_ptr<SetSiteSplitterFiltersCommand> command =
-            std::make_shared<SetSiteSplitterFiltersCommand>();
-        command->id      = *m_singleBuildingId;
-        command->filterA = collectFilter(m_filterAList);
-        command->filterB = collectFilter(m_filterBList);
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<CommandRequestedEvent>(command));
-    }
-    else
-    {
-        std::shared_ptr<SetSplitterFiltersCommand> command =
-            std::make_shared<SetSplitterFiltersCommand>();
-        command->tile    = m_splitterTile;
-        command->filterA = collectFilter(m_filterAList);
-        command->filterB = collectFilter(m_filterBList);
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<CommandRequestedEvent>(command));
-    }
-}
-
-std::vector<std::string> SelectedBuildingPanel::getAllItemIds() const
-{
-    std::set<std::string> seen;
-    for (const RecipeDef& recipe : m_config->recipes.recipes)
-    {
-        for (const RecipeIngredient& ing : recipe.inputs)
-        {
-            seen.insert(ing.item);
-        }
-        for (const RecipeOutput& out : recipe.outputs)
-        {
-            seen.insert(out.item);
-        }
-    }
-    return std::vector<std::string>(seen.begin(), seen.end());
-}
-
-void SelectedBuildingPanel::onClearBelt()
-{
-    std::vector<QPoint> tiles;
-    for (BuildingId id : m_selectedBuildingIds)
-    {
-        const Building* b = findBuilding(m_sim->getFactoryState(), id);
-        if (b && isBeltSubsystemType(b->type))
-        {
-            for (const QPoint& cell : b->bodyCells)
-            {
-                tiles.push_back(cell);
-            }
-        }
-    }
-    if (!tiles.empty())
-    {
-        std::shared_ptr<ClearBeltTilesCommand> command =
-            std::make_shared<ClearBeltTilesCommand>();
-        command->tiles = std::move(tiles);
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<CommandRequestedEvent>(command));
-    }
-}
-
-void SelectedBuildingPanel::handleEvent(std::shared_ptr<const EntitySelectionChangedEvent> event)
-{
-    m_fieldSelectionPanel->setSelectedEntities(event->entities);
-    yieldToFieldSelection();
-}
-
-void SelectedBuildingPanel::handleEvent(std::shared_ptr<const SelectionChangedEvent> event)
-{
-    onSelectionChanged(event->ids);
-}
-
-void SelectedBuildingPanel::handleEvent(
-    std::shared_ptr<const DebrisSelectionChangedEvent> event)
-{
-    // Debris is a field object: it supersedes any building selection but coexists
-    // with actors (REQ-UI-SELECTION-CATEGORIES).
-    m_fieldSelectionPanel->setSelectedDebris(event->debris);
-    yieldToFieldSelection();
-}

src/ui/SelectedBuildingPanel.h

@@ -1,122 +0,0 @@
-#pragma once
-
-#include <optional>
-#include <string>
-#include <vector>
-
-#include <QPoint>
-#include <QWidget>
-
-#include "BeltSystem.h"
-#include "Building.h"
-#include "BuildingId.h"
-#include "EntitySelectionChangedEvent.h"
-#include "EventHandler.h"
-#include "GameConfig.h"
-#include "PlayerCommandsAppliedEvent.h"
-#include "RecipesConfig.h"
-#include "DebrisSelectionChangedEvent.h"
-#include "SelectionChangedEvent.h"
-#include "ShipLayout.h"
-#include "ShipsConfig.h"
-#include "Tick.h"
-#include "TickAdvancedEvent.h"
-
-class Simulation;
-class FieldSelectionPanel;
-class ShipLayoutPreview;
-class QLabel;
-class QListWidget;
-class QPushButton;
-class QVBoxLayout;
-
-// Shows the current selection. The building category (buildings and construction sites)
-// is rendered by this panel itself; the field category (ships, defence stations, debris)
-// is rendered by the embedded FieldSelectionPanel.
-//
-// The two categories are mutually exclusive (REQ-UI-SELECTION-CATEGORIES) and this panel
-// is the sole arbiter of which one owns the content: it listens to all three selection
-// events, forwards the field ones to the child panel, and drops the losing category's
-// content. Neither panel touches the other's widgets.
-class SelectedBuildingPanel : public QWidget,
-                               public CombinedEventHandler<TickAdvancedEvent,
-                                                           PlayerCommandsAppliedEvent,
-                                                           EntitySelectionChangedEvent,
-                                                           SelectionChangedEvent,
-                                                           DebrisSelectionChangedEvent>
-{
-    Q_OBJECT
-
-public:
-    SelectedBuildingPanel(Simulation* sim, const GameConfig* config,
-                          QWidget* parent = nullptr);
-    ~SelectedBuildingPanel() override;
-
-private:
-    void handleEvent(std::shared_ptr<const TickAdvancedEvent> event) override;
-    void handleEvent(std::shared_ptr<const PlayerCommandsAppliedEvent> event) override;
-    void handleEvent(std::shared_ptr<const EntitySelectionChangedEvent> event) override;
-    void handleEvent(std::shared_ptr<const SelectionChangedEvent> event) override;
-    void handleEvent(std::shared_ptr<const DebrisSelectionChangedEvent> event) override;
-
-private slots:
-    void onSelectRecipeClicked();
-    void onClearBelt();
-    void onSplitterFilterChanged();
-
-private:
-    // Why the selection display is being refreshed. A periodic tick only needs a
-    // lightweight content update (e.g. a construction site's progress label),
-    // whereas an applied player command may have changed the configuration and
-    // needs a full structural rebuild.
-    enum class RefreshReason
-    {
-        PeriodicTick,
-        CommandApplied
-    };
-
-    void onSelectionChanged(const std::vector<BuildingId>& ids);
-    // Gives the panel to the field category once it has anything selected.
-    void yieldToFieldSelection();
-    void refreshSelectionDisplay(RefreshReason reason);
-    void rebuild();
-    void hideAllWidgets();
-    void buildEmpty();
-    void buildSingle(BuildingId id);
-    void buildMulti(const std::vector<BuildingId>& ids);
-    void refreshBuffers(const Building* b);
-    void refreshSiteProgress(const ConstructionSite* s);
-    void updateShipyardLayoutWidgets(BuildingType type,
-                                     const std::string& recipeId,
-                                     const std::optional<ShipLayoutConfig>& shipLayout);
-    void buildSplitterFilters(const std::optional<BeltSystem::SplitterInfo>& info);
-    const RecipeDef* findRecipe(const Building* b) const;
-    const ShipDef*   findShipDef(const std::string& id) const;
-    std::vector<std::string> getAllItemIds() const;
-
-    Simulation*        m_sim;
-    const GameConfig*  m_config;
-    std::vector<BuildingId> m_selectedBuildingIds;
-
-    QVBoxLayout* m_layout;
-    QLabel*      m_titleLabel;
-    QPushButton* m_recipeSelectButton;
-    QPushButton* m_clearBeltBtn;
-    QLabel*      m_filterALabel;
-    QListWidget* m_filterAList;
-    QLabel*      m_filterBLabel;
-    QListWidget* m_filterBList;
-    QLabel*      m_buffersLabel;
-
-    ShipLayoutPreview* m_layoutPreview;
-    QPushButton*       m_configureLayoutBtn;
-
-    std::optional<BuildingId> m_singleBuildingId;
-    bool         m_singleIsSite = false;  // selected single entity is a construction site
-    QPoint       m_splitterTile;
-    std::string  m_currentRecipeId;
-
-    // Renders the field selection (actors + debris) below the building content
-    // (REQ-UI-FIELD-MULTI-SELECTION). Hides itself while nothing field-side is selected.
-    FieldSelectionPanel* m_fieldSelectionPanel;
-};

src/ui/SelectionBounds.cpp

@@ -0,0 +1,115 @@
+#include "SelectionBounds.h"
+
+#include "Building.h"
+#include "DebrisComponent.h"
+#include "EntityAdmin.h"
+#include "FactoryQueries.h"
+#include "PositionComponent.h"
+#include "Simulation.h"
+#include "StationBodyComponent.h"
+#include "WorldCoordinates.h"
+#include "WorldPrimitives.h"
+
+namespace
+{
+
+// The widget rectangle of a footprint anchored at a tile, both kinds of body being
+// described the same way.
+QRectF getFootprintWidgetRect(const WorldCoordinates& coordinates, QPoint anchor,
+                              QSize footprint)
+{
+    const QPointF topLeft = coordinates.tileToWidget(anchor);
+    return QRectF(topLeft.x(), topLeft.y(),
+                  footprint.width()  * static_cast<qreal>(coordinates.getTilePx()),
+                  footprint.height() * static_cast<qreal>(coordinates.getTilePx()));
+}
+
+}  // namespace
+
+
+std::optional<QRectF> getBuildingWidgetRect(const FactoryState& state,
+                                            const WorldCoordinates& coordinates,
+                                            BuildingId id)
+{
+    if (const Building* building = findBuilding(state, id))
+    {
+        return getFootprintWidgetRect(coordinates, building->anchor, building->footprint);
+    }
+    if (const ConstructionSite* site = findSite(state, id))
+    {
+        return getFootprintWidgetRect(coordinates, site->anchor, site->footprint);
+    }
+    return std::nullopt;
+}
+
+std::optional<QRectF> getActorWidgetRect(const EntityAdmin& admin,
+                                         const WorldCoordinates& coordinates,
+                                         entt::entity actor)
+{
+    if (!admin.isValid(actor))
+    {
+        return std::nullopt;
+    }
+    if (admin.hasAll<StationBodyComponent>(actor))
+    {
+        const StationBodyComponent& body = admin.get<StationBodyComponent>(actor);
+        return getFootprintWidgetRect(coordinates, body.anchor, body.footprint);
+    }
+    if (admin.hasAll<PositionComponent>(actor))
+    {
+        // A ship is a triangle about its center; the square its longest extent fits in
+        // is what the panel is placed beside.
+        const QPointF center =
+            coordinates.worldToWidget(admin.get<PositionComponent>(actor).value);
+        const qreal extent = static_cast<qreal>(getShipForwardExtentPx(coordinates));
+        return QRectF(center.x() - extent, center.y() - extent,
+                      2.0 * extent, 2.0 * extent);
+    }
+    return std::nullopt;
+}
+
+std::optional<QRectF> getDebrisWidgetRect(const EntityAdmin& admin,
+                                          const WorldCoordinates& coordinates,
+                                          entt::entity debris)
+{
+    if (!admin.isValid(debris) || !admin.hasAll<PositionComponent, DebrisComponent>(debris))
+    {
+        return std::nullopt;
+    }
+    const QPointF center =
+        coordinates.worldToWidget(admin.get<PositionComponent>(debris).value);
+    const qreal radius = static_cast<qreal>(getDebrisRadiusPx(coordinates));
+    return QRectF(center.x() - radius, center.y() - radius, 2.0 * radius, 2.0 * radius);
+}
+
+QRect getSelectionWidgetRect(const Simulation& sim, const WorldCoordinates& coordinates,
+                             const std::vector<BuildingId>& buildings,
+                             const std::vector<entt::entity>& actors,
+                             const std::vector<entt::entity>& debris)
+{
+    QRectF bounds;
+    // A null rect unites to nothing of its own, so the first object found sets the box
+    // and every later one grows it.
+    auto add = [&bounds](const std::optional<QRectF>& rect)
+    {
+        if (rect.has_value())
+        {
+            bounds = bounds.isNull() ? *rect : bounds.united(*rect);
+        }
+    };
+
+    for (BuildingId id : buildings)
+    {
+        add(getBuildingWidgetRect(sim.getFactoryState(), coordinates, id));
+    }
+    for (entt::entity actor : actors)
+    {
+        add(getActorWidgetRect(sim.getAdmin(), coordinates, actor));
+    }
+    for (entt::entity piece : debris)
+    {
+        add(getDebrisWidgetRect(sim.getAdmin(), coordinates, piece));
+    }
+
+    return bounds.isNull() ? QRect() : bounds.toAlignedRect();
+}

src/ui/SelectionBounds.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include <optional>
+#include <vector>
+
+#include <QRect>
+
+#include "entt/entity/entity.hpp"
+
+#include "BuildingId.h"
+
+class EntityAdmin;
+class Simulation;
+class WorldCoordinates;
+struct FactoryState;
+
+// Where selectable objects are on the screen. The world renderer draws every selection
+// outline from these rectangles, and the selection panel is placed beside the one that
+// covers the whole selection (REQ-UI-SELECTION-PANEL).
+//
+// All of them are in the game world view's own widget coordinates, and all of them are
+// only true for the WorldCoordinates they were asked for: the transform is a value built
+// per frame or per event, so a rectangle does not survive a scroll or a resize.
+
+// The footprint of a building or of a construction site (REQ-UI-SELECTION-CARD). Null
+// when the id names neither, which is what a deconstruction under the caller looks like.
+std::optional<QRectF> getBuildingWidgetRect(const FactoryState& state,
+                                            const WorldCoordinates& coordinates,
+                                            BuildingId id);
+
+// The body of a ship or of a defence station (REQ-UI-ENTITY-CLICK-SELECT): a station's
+// footprint, or the square the ship's triangle is drawn in.
+std::optional<QRectF> getActorWidgetRect(const EntityAdmin& admin,
+                                         const WorldCoordinates& coordinates,
+                                         entt::entity actor);
+
+// The circle a piece of debris is drawn as (REQ-UI-DEBRIS-CLICK-SELECT).
+std::optional<QRectF> getDebrisWidgetRect(const EntityAdmin& admin,
+                                          const WorldCoordinates& coordinates,
+                                          entt::entity debris);
+
+// The rectangle covering a whole selection -- one object, or the bounding box of all of
+// them (REQ-UI-SELECTION-PANEL). Objects that no longer resolve are skipped; the result
+// is null when none of them does.
+QRect getSelectionWidgetRect(const Simulation& sim, const WorldCoordinates& coordinates,
+                             const std::vector<BuildingId>& buildings,
+                             const std::vector<entt::entity>& actors,
+                             const std::vector<entt::entity>& debris);

src/ui/SelectionPanel.cpp

@@ -0,0 +1,431 @@
+#include "SelectionPanel.h"
+
+#include <QMouseEvent>
+#include <QScrollArea>
+#include <QScrollBar>
+#include <QVBoxLayout>
+
+#include "BuildingIconCache.h"
+#include "EventManager.h"
+#include "FloatingLayoutInvalidatedEvent.h"
+#include "FloatingPanelPlacement.h"
+#include "ItemIconCache.h"
+#include "Simulation.h"
+#include "VisualsConfig.h"
+#include "selection/SelectionContent.h"
+
+namespace
+{
+
+// The edge margin: the distance kept between the panel and the edges of the game world
+// view, and between it and the widgets it steps around (REQ-UI-SELECTION-PANEL). The gap
+// the panel keeps from the selection itself is the wider of the two and is not this: being
+// half a tile, it is measured where the tile size is known and arrives with the anchor
+// rectangle (SelectionAnchorChangedEvent).
+const int kMarginPx = 8;
+
+// Upper bound on the card width. The panel is content-sized, but several of the cards'
+// widgets have no natural width of their own -- the word-wrapped summary labels grow
+// without limit, and a QListWidget asks for 256 px whatever it holds -- so the width is
+// capped and the labels wrap at the cap. 320 px is the width the former side panel
+// column had at the default window size.
+const int kMaxContentWidthPx = 320;
+
+// Padding between the panel's border and the card inside it.
+const int kCardMarginPx = 8;
+
+}  // namespace
+
+
+SelectionPanel::SelectionPanel(Simulation* sim, const GameConfig* config,
+                               const VisualsConfig* visuals, ItemIconCache* itemIcons,
+                               BuildingIconCache* buildingIcons, QWidget* parent)
+    : QWidget(parent)
+{
+    m_context.sim              = sim;
+    m_context.config           = config;
+    m_context.visuals          = visuals;
+    m_context.itemIcons        = itemIcons;
+    m_context.buildingIcons    = buildingIcons;
+    m_context.debugDrawEnabled = &m_debugDrawEnabled;
+
+    // The panel floats over the rendered world rather than sitting in a column, so it
+    // brings its own opaque background to stay legible over any world content
+    // (REQ-UI-SELECTION-PANEL). Palette colors match the build button bar's chrome; like
+    // it, this is widget chrome rather than world rendering, so it is deliberately not a
+    // visuals.toml color. The class scoped selector keeps the border on the panel itself
+    // rather than cascading onto its child widgets.
+    setAttribute(Qt::WA_StyledBackground, true);
+    setStyleSheet(QStringLiteral(
+        "SelectionPanel { background-color: palette(window);"
+        " border: 1px solid palette(mid); border-radius: 4px; }"));
+
+    // A card taller than the band scrolls rather than overrunning it
+    // (REQ-UI-SELECTION-PANEL). The viewport is transparent so the panel's own rounded
+    // chrome shows through, and horizontal scrolling is off because the width always
+    // follows the content.
+    m_body = new QWidget(this);
+    m_scrollArea = new QScrollArea(this);
+    m_scrollArea->setFrameShape(QFrame::NoFrame);
+    m_scrollArea->setWidgetResizable(true);
+    m_scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    // The panel works out for itself whether the card fits the band, and sizes itself to
+    // leave room for the bar when it does not (REQ-UI-SELECTION-PANEL), so refit() sets
+    // this policy rather than leaving the scroll area to decide. Asked to decide, it
+    // shows a bar the moment the card is momentarily larger than the viewport -- which
+    // happens while the card is being measured -- and does not take it back when the
+    // range turns out to be empty.
+    m_scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    m_scrollArea->viewport()->setAutoFillBackground(false);
+    m_body->setAutoFillBackground(false);
+    m_scrollArea->setWidget(m_body);
+
+    QVBoxLayout* outerLayout = new QVBoxLayout(this);
+    outerLayout->setContentsMargins(0, 0, 0, 0);
+    outerLayout->setSpacing(0);
+    outerLayout->addWidget(m_scrollArea);
+
+    m_bodyLayout = new QVBoxLayout(m_body);
+    m_bodyLayout->setContentsMargins(kCardMarginPx, kCardMarginPx,
+                                     kCardMarginPx, kCardMarginPx);
+    m_bodyLayout->setSpacing(0);
+    m_bodyLayout->setAlignment(Qt::AlignTop);
+
+    hide();
+
+    registerForEvents();
+}
+
+SelectionPanel::~SelectionPanel()
+{
+    unregisterForEvents();
+}
+
+void SelectionPanel::invalidateLayout()
+{
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<FloatingLayoutInvalidatedEvent>());
+}
+
+void SelectionPanel::mousePressEvent(QMouseEvent* event)
+{
+    // Only the card's header moves the panel (REQ-UI-SELECTION-PANEL-DRAG). Presses on
+    // the header's labels arrive here by ordinary propagation, none of them being a
+    // widget that accepts mouse events, and carry a position in this panel's coordinates.
+    if (event->button() == Qt::LeftButton && m_content != nullptr)
+    {
+        QWidget* header = m_content->getHeaderWidget();
+        QRect headerRect(header->mapTo(this, QPoint(0, 0)), header->size());
+        // A card long enough to scroll can have its header scrolled out of sight; what is
+        // hidden is not a handle, and the pixels it would claim show other parts of the
+        // card.
+        QWidget* viewport = m_scrollArea->viewport();
+        headerRect &= QRect(viewport->mapTo(this, QPoint(0, 0)), viewport->size());
+        if (headerRect.contains(event->pos()))
+        {
+            m_dragGrabOffsetPx = event->pos();
+        }
+    }
+
+    // Accepted whether or not it started a drag: no mouse event over the panel reaches
+    // the game world (REQ-UI-SELECTION-PANEL).
+    event->accept();
+}
+
+void SelectionPanel::mouseMoveEvent(QMouseEvent* event)
+{
+    if (m_dragGrabOffsetPx.has_value() && parentWidget() != nullptr)
+    {
+        // Read from the cursor's position on the screen rather than from the panel's own
+        // coordinates, which move under the cursor as the drag places the panel again.
+        const QPoint topLeftPx =
+            parentWidget()->mapFromGlobal(event->globalPos()) - *m_dragGrabOffsetPx;
+        m_desiredTopLeftPx = topLeftPx - m_viewOriginPx;
+        // Where the panel actually lands follows from the desired position by the
+        // ordinary rules, the widgets it steps around included (REQ-UI-SELECTION-PANEL-DRAG).
+        invalidateLayout();
+    }
+    event->accept();
+}
+
+void SelectionPanel::mouseReleaseEvent(QMouseEvent* event)
+{
+    // Qt's implicit grab has kept the drag alive while the cursor was outside the panel
+    // or outside the view; it ends here, wherever the button was let go
+    // (REQ-UI-SELECTION-PANEL-DRAG). The desired position stays as dropped.
+    m_dragGrabOffsetPx.reset();
+    event->accept();
+}
+
+void SelectionPanel::handleEvent(std::shared_ptr<const SelectionChangedEvent> event)
+{
+    m_request.buildings = event->ids;
+    if (!m_request.buildings.empty())
+    {
+        // A building selection is exclusive: it supersedes any field selection -- actors
+        // and scrap alike (REQ-UI-SELECTION-CATEGORIES).
+        m_request.actors.clear();
+        m_request.debris.clear();
+    }
+    rebuildContent();
+}
+
+void SelectionPanel::handleEvent(
+    std::shared_ptr<const SelectionAnchorChangedEvent> event)
+{
+    // A new selection is starting. The anchor, the gap kept from it, and the side are all
+    // settled against it and then left alone for as long as it lasts
+    // (REQ-UI-SELECTION-PANEL); the side is only reset here, being resolved on the next
+    // placement once the card's width is known. The rect arrives in the world view's
+    // coordinates and is translated when the panel is placed, the two widgets being
+    // siblings in the same parent.
+    m_anchorRect      = event->rectPx;
+    m_selectionGapPx  = event->selectionGapPx;
+    m_side.reset();
+    // A position the player dragged the panel to belongs to the selection it was set in.
+    // A new selection places the panel anew against its own anchor
+    // (REQ-UI-SELECTION-PANEL-DRAG); this event is published only when one starts, and
+    // not when an existing selection is added to or reduced, which is exactly the scope
+    // the dragged position keeps.
+    m_desiredTopLeftPx.reset();
+    m_dragGrabOffsetPx.reset();
+}
+
+void SelectionPanel::handleEvent(
+    std::shared_ptr<const EntitySelectionChangedEvent> event)
+{
+    m_request.actors = event->entities;
+    if (!m_request.actors.empty() || !m_request.debris.empty())
+    {
+        m_request.buildings.clear();
+    }
+    rebuildContent();
+}
+
+void SelectionPanel::handleEvent(
+    std::shared_ptr<const DebrisSelectionChangedEvent> event)
+{
+    // Debris is a field object: it supersedes any building selection but coexists with
+    // actors (REQ-UI-SELECTION-CATEGORIES).
+    m_request.debris = event->debris;
+    if (!m_request.actors.empty() || !m_request.debris.empty())
+    {
+        m_request.buildings.clear();
+    }
+    rebuildContent();
+}
+
+void SelectionPanel::handleEvent(std::shared_ptr<const TickAdvancedEvent> /*event*/)
+{
+    refreshContent();
+}
+
+void SelectionPanel::handleEvent(
+    std::shared_ptr<const PlayerCommandsAppliedEvent> /*event*/)
+{
+    // Player commands (choosing a shipyard schematic, say) are applied by a queued
+    // drain, not synchronously. When the game is paused no tick advances, so
+    // TickAdvancedEvent never fires; refreshing here too is what makes the change show
+    // up without waiting for a tick or a re-selection.
+    refreshContent();
+}
+
+void SelectionPanel::handleEvent(std::shared_ptr<const DebugDrawToggledEvent> event)
+{
+    m_debugDrawEnabled = event->active;
+}
+
+void SelectionPanel::refreshContent()
+{
+    if (!m_content)
+    {
+        return;
+    }
+
+    // A card never changes its own shape, so when the selection now calls for a
+    // different one it is replaced rather than refreshed. Only a single selected
+    // building can reach that state without the selection itself changing -- its
+    // construction site finishes, or it is deconstructed under the panel. Everything
+    // else is re-published as a selection change, so re-deriving the key here would walk
+    // a large multi-selection every tick to learn nothing.
+    if (m_request.buildings.size() == 1
+        && chooseContent(m_request, *m_context.sim) != m_contentKey)
+    {
+        rebuildContent();
+        return;
+    }
+
+    m_content->refresh();
+    invalidateLayout();
+}
+
+void SelectionPanel::rebuildContent()
+{
+    if (m_content)
+    {
+        // Retired rather than deleted: a rebuild can be reached from inside one of the
+        // card's own click handlers -- the recipe control opens a modal dialog and the
+        // choice comes back as a command -- and control has to be able to return into
+        // the widget that is going away.
+        m_content->hide();
+        m_content->deleteLater();
+        m_content = nullptr;
+    }
+
+    m_contentKey = chooseContent(m_request, *m_context.sim);
+    m_content = createContent(m_contentKey, m_request, m_context, m_body);
+    if (m_content)
+    {
+        m_bodyLayout->addWidget(m_content);
+        // The show is what makes the card count. A widget created under an
+        // already-visible parent starts hidden, and a layout treats a hidden item as
+        // empty -- it adds nothing to the size hint until something shows it, which
+        // otherwise does not happen until the event loop next runs, long after refit()
+        // has measured the panel. The panel then fits itself to an empty body and
+        // collapses to its scroll bar.
+        m_content->show();
+        m_content->refresh();
+    }
+    invalidateLayout();
+}
+
+void SelectionPanel::placeIn(const QRect& viewRect, const std::vector<QRect>& occupiedRects)
+{
+    // Nothing selected in either category means no panel at all rather than an empty one
+    // (REQ-UI-EMPTY-SELECTION), leaving the whole game world view visible.
+    setVisible(m_content != nullptr);
+    if (m_content == nullptr || viewRect.isNull())
+    {
+        return;
+    }
+
+    const QRect band = viewRect.adjusted(kMarginPx, kMarginPx, -kMarginPx, -kMarginPx);
+
+    // What the view's coordinates and this panel's differ by, kept for the drag gesture,
+    // which learns of the cursor in the latter and stores its result in the former
+    // (REQ-UI-SELECTION-PANEL-DRAG).
+    m_viewOriginPx = viewRect.topLeft();
+
+    // The anchor is published in the world view's coordinates and this panel is placed in
+    // its parent's; the two widgets are siblings, so the view's own origin is the whole
+    // difference. Without an anchor the panel falls back to the top-right corner, by
+    // standing beside a point just outside that corner -- in practice unreachable, every
+    // non-empty selection following a click or a drag that publishes one.
+    const QRect anchorRect =
+        m_anchorRect.isNull() ? QRect(band.right() + kMarginPx + 1, band.top(), 1, 1)
+                              : m_anchorRect.translated(viewRect.topLeft());
+
+    // The panel's border is drawn around the scroll area rather than around the card, so
+    // it is added to whatever the card asks for. Spelled out here instead of read back
+    // from contentsMargins() because the stylesheet box is what sets it, and asking the
+    // style for it before the first show is unreliable.
+    const int borderPx   = 1;
+    const int maxWidthPx = qMin(kMaxContentWidthPx, band.width() - 2 * borderPx);
+    if (maxWidthPx <= 0 || band.height() <= 2 * borderPx)
+    {
+        return;
+    }
+
+    // What the card asks for at a given width. The width has to be applied before
+    // asking, because a card's height depends on the room it is given -- and so, once
+    // laid out, does the width it reports. Measuring at whatever width the panel
+    // happens to have carries the previous card's shape into this one.
+    //
+    // Each measurement re-runs the body layout. Cards are built and discarded whole, so
+    // its cached hint describes the card before this one until it is invalidated, and
+    // re-running it is also what accounts for the parts a card hides and shows as it
+    // refreshes. The polish belongs to the same step: a freshly created chip reports an
+    // unstyled hint until the stylesheet has reached it, and the chips carry border and
+    // padding that change their size.
+    auto measureAt = [this](int widthPx) -> QSize
+    {
+        m_body->resize(widthPx, m_body->height());
+        m_body->ensurePolished();
+        m_body->layout()->invalidate();
+        m_body->layout()->activate();
+        return m_body->sizeHint();
+    };
+
+    // Where a panel of that size stands: beside the selection, or at the position the
+    // player dragged the panel to, which replaces both the anchor and the side for the
+    // rest of the selection (REQ-UI-SELECTION-PANEL-DRAG). Either way the result is
+    // resolved against the view's edges and the widgets placed before this one, so a
+    // dragged panel steps around them exactly as an anchored one does.
+    auto solve = [&](QSize wantedSize) -> QRect
+    {
+        if (m_desiredTopLeftPx.has_value())
+        {
+            return placeAtDesiredTopLeft(band, *m_desiredTopLeftPx + viewRect.topLeft(),
+                                         wantedSize, occupiedRects, kMarginPx);
+        }
+        return placeBesideAnchor(band, anchorRect, *m_side, wantedSize, occupiedRects,
+                                 m_selectionGapPx, kMarginPx);
+    };
+
+    // Run twice. Parts of a card report an unstyled size until the style has actually
+    // reached them, which for a freshly built card happens during the first round of
+    // measuring; the second round then measures a card that is fully laid out and
+    // settles on the answer. Without it a card can end up a few pixels short of what it
+    // turns out to need, and the difference shows as a scroll bar over a card that
+    // looks like it fits.
+    for (int pass = 0; pass < 2; ++pass)
+    {
+        // First at the cap, the most room the card can ever get, to learn how wide it
+        // wants to be; then at that width for the height that follows from it.
+        int contentWidthPx  = qMin(measureAt(maxWidthPx).width(), maxWidthPx);
+
+        // Which side of the selection the panel takes is settled on the first placement
+        // after a new anchor and kept for as long as that selection lasts, so a card that
+        // grows or shrinks never flips the panel across the object it describes
+        // (REQ-UI-SELECTION-PANEL). This is the first point at which its width is known.
+        if (!m_side.has_value())
+        {
+            m_side = chooseSide(band, anchorRect, contentWidthPx + 2 * borderPx,
+                                m_selectionGapPx);
+        }
+
+        // How much height there is depends on where the panel ends up standing: of the
+        // widgets placed before it, only those whose rectangles meet its own column are
+        // in its way. That column follows from the width just measured, so this cannot be
+        // settled before it -- and where the scroll bar below widens the panel, the second
+        // pass settles it again against the wider column. Asking for the whole band's
+        // height is what makes the answer the most the panel could have there.
+        const int maxHeightPx =
+            solve(QSize(contentWidthPx + 2 * borderPx, band.height())).height()
+            - 2 * borderPx;
+        if (maxHeightPx <= 0)
+        {
+            return;
+        }
+
+        int contentHeightPx = measureAt(contentWidthPx).height();
+
+        // A card taller than the space left is capped there and scrolls
+        // (REQ-UI-SELECTION-PANEL). The bar is laid out beside the card, so the panel
+        // widens by its width to leave the card the width its height was measured for --
+        // and where the cap does not allow that, the card is measured again at what is
+        // left over.
+        const bool scrolls = (contentHeightPx > maxHeightPx);
+        int viewportWidthPx = contentWidthPx;
+        if (scrolls)
+        {
+            const int scrollBarWidthPx =
+                m_scrollArea->verticalScrollBar()->sizeHint().width();
+            contentWidthPx  = qMin(contentWidthPx + scrollBarWidthPx, maxWidthPx);
+            contentHeightPx = maxHeightPx;
+            viewportWidthPx = contentWidthPx - scrollBarWidthPx;
+            measureAt(viewportWidthPx);
+        }
+        m_scrollArea->setVerticalScrollBarPolicy(
+            scrolls ? Qt::ScrollBarAlwaysOn : Qt::ScrollBarAlwaysOff);
+
+        // Left at the size the scroll area is about to give it, so the card is not
+        // briefly wider than its viewport.
+        m_body->resize(viewportWidthPx, m_body->sizeHint().height());
+
+        const int panelWidthPx  = contentWidthPx + 2 * borderPx;
+        const int panelHeightPx = contentHeightPx + 2 * borderPx;
+
+        setGeometry(solve(QSize(panelWidthPx, panelHeightPx)));
+    }
+}

src/ui/SelectionPanel.h

@@ -0,0 +1,135 @@
+#pragma once
+
+#include <QPoint>
+#include <QRect>
+#include <QWidget>
+
+#include <optional>
+#include <vector>
+
+#include "DebrisSelectionChangedEvent.h"
+#include "DebugDrawToggledEvent.h"
+#include "EntitySelectionChangedEvent.h"
+#include "EventHandler.h"
+#include "FloatingPanel.h"
+#include "FloatingPanelPlacement.h"
+#include "PlayerCommandsAppliedEvent.h"
+#include "SelectionAnchorChangedEvent.h"
+#include "SelectionChangedEvent.h"
+#include "TickAdvancedEvent.h"
+#include "selection/SelectionContentFactory.h"
+#include "selection/SelectionContext.h"
+
+struct GameConfig;
+struct VisualsConfig;
+class BuildingIconCache;
+class ItemIconCache;
+class SelectionContent;
+class Simulation;
+class QMouseEvent;
+class QScrollArea;
+class QVBoxLayout;
+
+// Shows the current selection. The panel itself renders nothing: it arbitrates between
+// the two selection categories (REQ-UI-SELECTION-CATEGORIES), picks the card that fits
+// what is selected (REQ-UI-SELECTION-CONTENT), and hosts exactly one of them at a time.
+// What each card looks like lives in src/ui/selection/.
+//
+// The panel floats over the game world view rather than occupying a column of its own
+// (REQ-UI-SELECTION-PANEL): it sizes itself to its card, places itself in what the build
+// button bar and the controls panel have left free, and hides itself entirely while
+// nothing is selected (REQ-UI-EMPTY-SELECTION).
+class SelectionPanel : public QWidget,
+                       public FloatingPanel,
+                       public CombinedEventHandler<TickAdvancedEvent,
+                                                   PlayerCommandsAppliedEvent,
+                                                   EntitySelectionChangedEvent,
+                                                   SelectionChangedEvent,
+                                                   SelectionAnchorChangedEvent,
+                                                   DebrisSelectionChangedEvent,
+                                                   DebugDrawToggledEvent>
+{
+    Q_OBJECT
+
+public:
+    // visuals, itemIcons and buildingIcons are window-wide rendering resources the cards
+    // draw from; none is owned and all must outlive this widget.
+    SelectionPanel(Simulation* sim, const GameConfig* config,
+                   const VisualsConfig* visuals, ItemIconCache* itemIcons,
+                   BuildingIconCache* buildingIcons, QWidget* parent = nullptr);
+    ~SelectionPanel() override;
+
+    // Sizes the panel to its card and places it beside the selection it describes, in
+    // what the widgets placed before it have left free. Keeping clear of them is entirely
+    // this panel's job; neither of them ever moves for it (REQ-UI-SELECTION-PANEL,
+    // REQ-UI-BUILD-BAR, REQ-UI-CONTROLS-PANEL).
+    void placeIn(const QRect& viewRect,
+                 const std::vector<QRect>& occupiedRects) override;
+
+protected:
+    // The panel is moved by dragging its card header (REQ-UI-SELECTION-PANEL-DRAG). Every
+    // other mouse event over the panel is swallowed here so that none of them reaches the
+    // game world beneath (REQ-UI-SELECTION-PANEL).
+    void mousePressEvent(QMouseEvent* event) override;
+    void mouseMoveEvent(QMouseEvent* event) override;
+    void mouseReleaseEvent(QMouseEvent* event) override;
+
+private:
+    void handleEvent(std::shared_ptr<const SelectionChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const SelectionAnchorChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const EntitySelectionChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const DebrisSelectionChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const TickAdvancedEvent> event) override;
+    void handleEvent(std::shared_ptr<const PlayerCommandsAppliedEvent> event) override;
+    void handleEvent(std::shared_ptr<const DebugDrawToggledEvent> event) override;
+
+    // Re-reads the live values of the card on screen. When the selection now calls for a
+    // different card -- a construction site finishing is the case that matters -- it
+    // rebuilds instead, because a card never changes its own shape.
+    void refreshContent();
+    // Replaces the card with the one the current selection calls for.
+    void rebuildContent();
+    // Asks for the placement pass to be re-run, the card having changed size or the
+    // panel having gained or lost its reason to be shown at all.
+    void invalidateLayout();
+
+    SelectionContext m_context;
+    // Read through m_context by the cards that need it, so a toggle reaches the card on
+    // screen without it having to subscribe to the event itself.
+    bool m_debugDrawEnabled = false;
+
+    SelectionRequest  m_request;
+    ContentKey        m_contentKey;
+    SelectionContent* m_content = nullptr;
+
+    // Where the current selection was on the screen when it started, in the game world
+    // view's coordinates, the gap the panel keeps from it, and which side of it the panel
+    // took. All three are frozen for as long as the selection lasts: the anchor because
+    // the panel does not chase a scrolling view or a moving ship, the gap because it is
+    // measured against that frozen rectangle, the side because a card that grows must not
+    // flip the panel across the object (REQ-UI-SELECTION-PANEL). The side is resolved on
+    // the first placement after a new anchor, being the first point at which the panel's
+    // width is known. Dragging the panel supersedes all three for the rest of the
+    // selection (REQ-UI-SELECTION-PANEL-DRAG).
+    QRect                    m_anchorRect;
+    int                      m_selectionGapPx = 0;
+    std::optional<PanelSide> m_side;
+
+    // Where the player dragged the panel, in the game world view's coordinates, and the
+    // cursor's offset within the panel while a drag is running
+    // (REQ-UI-SELECTION-PANEL-DRAG). The desired position is kept exactly as dropped:
+    // resolving it against the view's edges and the widgets the panel steps around never
+    // writes back to it, so the panel returns to it once the room is there again. It
+    // lasts as long as the selection it was set in.
+    std::optional<QPoint> m_desiredTopLeftPx;
+    std::optional<QPoint> m_dragGrabOffsetPx;
+    // Origin of the view the panel was last placed in, which is what the two coordinate
+    // systems differ by -- the panel is a sibling of the view, not a child of it.
+    QPoint m_viewOriginPx;
+
+    // Scrolls the card once it outgrows the space the panel has (REQ-UI-SELECTION-PANEL).
+    // The card is a child of m_body, not of the panel itself.
+    QScrollArea* m_scrollArea;
+    QWidget*     m_body;
+    QVBoxLayout* m_bodyLayout;
+};

src/ui/ShipLayoutDialog.cpp

@@ -4,12 +4,18 @@
 #include <cmath>
 #include <functional>
 
+#include "DialogDismiss.h"
 #include "DisplayName.h"
+#include "OptionButton.h"
+#include "ProductionRules.h"
+#include "RecipeLineRow.h"
+#include "SectionBox.h"
 
 #include <QGridLayout>
 #include <QHBoxLayout>
 #include <QInputDialog>
 #include <QKeyEvent>
+#include <QLabel>
 #include <QMouseEvent>
 #include <QPainter>
 #include <QPushButton>
@@ -22,6 +28,18 @@
 namespace
 {
 
+std::vector<RecipeLineRow::Amount> toAmounts(
+    const std::vector<RecipeIngredient>& ingredients)
+{
+    std::vector<RecipeLineRow::Amount> amounts;
+    amounts.reserve(ingredients.size());
+    for (const RecipeIngredient& ingredient : ingredients)
+    {
+        amounts.push_back(RecipeLineRow::Amount{ ingredient.item, ingredient.amount });
+    }
+    return amounts;
+}
+
 const int kCellSize = 32;
 
 // Empty ship tiles pulse between this grey and white at 1 Hz while a module is
@@ -401,9 +419,11 @@ ShipLayoutDialog::ShipLayoutDialog(const GameConfig* config,
                                    std::vector<ShipLayoutBlueprint>& allBlueprints,
                                    std::set<std::string> unlockedModuleIds,
                                    bool debugDraw,
+                                   ItemIconCache* itemIcons,
                                    QWidget* parent)
     : QDialog(parent)
     , m_config(config)
+    , m_itemIcons(itemIcons)
     , m_shipId(shipId)
     , m_unlockedModuleIds(std::move(unlockedModuleIds))
     , m_rows(0)
@@ -463,10 +483,22 @@ ShipLayoutDialog::ShipLayoutDialog(const GameConfig* config,
     // Middle: three-column area (stats | module buttons | blueprints).
     QHBoxLayout* columnsLayout = new QHBoxLayout();
 
-    // Left column: ship stats panel.
+    // Left column: ship stats panel, and beneath it what the layout being configured
+    // would cost to build (REQ-MOD-UI-DIALOG). The cost sits outside the stats panel
+    // because that widget is shared with the live ship card and the balancing tool,
+    // neither of which costs anything -- and the balancing tool is deliberately built
+    // without the item icons this line draws with.
+    QVBoxLayout* leftLayout = new QVBoxLayout();
     m_statsPanel = new ShipStatsPanel(config, this);
     m_statsPanel->setDebugDrawEnabled(m_debugDraw);
-    columnsLayout->addWidget(m_statsPanel);
+    leftLayout->addWidget(m_statsPanel);
+
+    m_buildCostSection = new SectionBox(tr("Build cost"), this);
+    m_buildCostLine    = new RecipeLineRow(m_itemIcons, nullptr, m_buildCostSection);
+    m_buildCostSection->getContentLayout()->addWidget(m_buildCostLine);
+    leftLayout->addWidget(m_buildCostSection);
+    leftLayout->addStretch(1);
+    columnsLayout->addLayout(leftLayout);
 
     // Center column: module selection buttons.
     QVBoxLayout* centerLayout = new QVBoxLayout();
@@ -487,11 +519,34 @@ ShipLayoutDialog::ShipLayoutDialog(const GameConfig* config,
             m_moduleButtons.push_back(nullptr);
             continue;
         }
-        const QString label = QString::fromStdString(toDisplayName(def.id))
-            + "\n" + QString::fromStdString(def.glyph);
-        QPushButton* btn = new QPushButton(label, this);
+        // The module's name over what it costs -- its materials and the production time
+        // it adds (REQ-MOD-UI-DIALOG). The glyph is how a module is identified on the
+        // layout grid, not here. Both children are transparent to the mouse so a click
+        // anywhere on the face still reaches the button.
+        OptionButton* btn = new OptionButton(this);
         btn->setCheckable(true);
-        btn->setFixedHeight(48);
+
+        QVBoxLayout* face = new QVBoxLayout(btn);
+        face->setContentsMargins(8, 4, 8, 4);
+        face->setSpacing(1);
+
+        QLabel* nameLabel =
+            new QLabel(QString::fromStdString(toDisplayName(def.id)), btn);
+        nameLabel->setAttribute(Qt::WA_TransparentForMouseEvents, true);
+        face->addWidget(nameLabel);
+
+        RecipeLineRow::Spec cost;
+        cost.inputs             = toAmounts(def.materials);
+        cost.durationSeconds    = def.productionTimeSeconds;
+        cost.durationIsAddition = true;
+
+        RecipeLineRow* costLine = new RecipeLineRow(m_itemIcons, nullptr, btn);
+        costLine->setAttribute(Qt::WA_TransparentForMouseEvents, true);
+        face->addWidget(costLine);
+        costLine->setLine(cost);
+
+        // The config tooltip stays: it says what the module does, which the cost line
+        // does not (REQ-MOD-UI-MODULE-TOOLTIP).
         if (def.tooltip)
         {
             btn->setToolTip(QString::fromStdString(*def.tooltip));
@@ -521,24 +576,8 @@ ShipLayoutDialog::ShipLayoutDialog(const GameConfig* config,
         ++row;
     }
     buttonGrid->addWidget(m_removeButton, row, 0, 1, kCols);
-    connect(m_removeButton, &QPushButton::clicked, this, [this]() {
-        if (m_removeMode)
-        {
-            m_removeMode = false;
-            m_removeButton->setChecked(false);
-        }
-        else
-        {
-            for (QPushButton* btn : m_moduleButtons)
-            {
-                if (btn) { btn->setChecked(false); }
-            }
-            m_activeModuleIndex = std::nullopt;
-            m_removeMode = true;
-            m_removeButton->setChecked(true);
-        }
-        updateGridWidget();
-    });
+    connect(m_removeButton, &QPushButton::clicked,
+            this, &ShipLayoutDialog::onRemoveButtonClicked);
 
     centerLayout->addLayout(buttonGrid);
     centerLayout->addStretch();
@@ -643,6 +682,16 @@ void ShipLayoutDialog::keyPressEvent(QKeyEvent* event)
         }
         updateGridWidget();
     }
+    else if (isDialogDismissKey(*event))
+    {
+        // Q backs out one level per press, as it does in the game world: the module
+        // being placed, then remove mode, then the dialog itself, which discards the
+        // session (REQ-UI-DIALOG-DISMISS). Both mode exits go through the handler the
+        // button uses, so the key and the button can never leave different state behind.
+        if (m_activeModuleIndex.has_value()) { onModuleButtonClicked(*m_activeModuleIndex); }
+        else if (m_removeMode)               { onRemoveButtonClicked(); }
+        else                                 { onCancel(); }
+    }
     else
     {
         QDialog::keyPressEvent(event);
@@ -669,6 +718,26 @@ void ShipLayoutDialog::onModuleButtonClicked(int index)
     updateGridWidget();
 }
 
+void ShipLayoutDialog::onRemoveButtonClicked()
+{
+    if (m_removeMode)
+    {
+        m_removeMode = false;
+        m_removeButton->setChecked(false);
+    }
+    else
+    {
+        for (QPushButton* btn : m_moduleButtons)
+        {
+            if (btn) { btn->setChecked(false); }
+        }
+        m_activeModuleIndex = std::nullopt;
+        m_removeMode = true;
+        m_removeButton->setChecked(true);
+    }
+    updateGridWidget();
+}
+
 void ShipLayoutDialog::onConfirm()
 {
     ShipLayoutConfig layout;
@@ -731,6 +800,29 @@ void ShipLayoutDialog::updateGridWidget()
 void ShipLayoutDialog::updateStats()
 {
     m_statsPanel->refresh(m_shipId, m_placedModules);
+
+    // What the layout as it currently stands would cost to build, so the price follows
+    // every placement and removal (REQ-MOD-UI-DIALOG). The sums come from the
+    // simulation's own rules rather than being added up a second time here
+    // (REQ-MOD-MATERIALS, REQ-MOD-PRODUCTION-TIME).
+    ShipLayoutConfig layout;
+    layout.placedModules = m_placedModules;
+    const std::map<std::string, int> materials =
+        computeShipyardRequiredMaterials(*m_config, m_shipId, layout);
+
+    RecipeLineRow::Spec cost;
+    cost.inputs.reserve(materials.size());
+    for (const std::pair<const std::string, int>& entry : materials)
+    {
+        cost.inputs.push_back(RecipeLineRow::Amount{ entry.first, entry.second });
+    }
+    cost.durationSeconds =
+        computeShipyardProductionTimeSeconds(*m_config, m_shipId, layout);
+
+    m_buildCostLine->setLine(cost);
+    // A schematic costing no materials at all has no line to draw, and the section then
+    // stays out of the way.
+    m_buildCostSection->setVisible(!cost.inputs.empty());
 }
 
 bool ShipLayoutDialog::canPlaceModule(const ModuleDef& def, QPoint position,