make recipe selection and buffers of smelter and reprocessing plant behave like other buildings, except that a recipe may be chosen automatically

.claude/CLAUDE.md

@@ -60,6 +60,13 @@ keep the citation accurate.
 * don't use abbreviations, except very common ones ("s" for seconds, "min", "max", etc.)
 * if a variable holds a value that has a unit or if a function returns a value that has a unit, append that unit to the name (e.g. "m_shipVelocity_mps", "getAcceleration_mpss()")
 * always enclose scopes in braces
+* keep source files ASCII-only. A non-ASCII character needed at runtime (a glyph in a
+  UI string, a symbol drawn on a widget) is written as its code point with a comment
+  naming it (`const QChar shiftGlyph(0x21E7);  // U+21E7 UPWARDS WHITE ARROW`), never
+  as a literal character: MSVC 2017 does not read the sources as UTF-8 by default and
+  silently mangles them. Never round-trip a source file through
+  `Get-Content`/`Set-Content` either: Windows PowerShell reads it as ANSI and writes
+  it back double-encoded with a BOM. Use the Edit/Write tools.
 
 ## Build
 
@@ -96,6 +103,15 @@ output directories and copies the Qt DLLs.
 Run the app: `build/DotaFactory/Debug/app/DotaFactory.exe`, optionally
 `--replay <file>` for view-only playback of a recorded run.
 
+**Visual verification is the user's job.** Screen-capturing the app window does not
+work here: `CopyFromScreen` and `PrintWindow` both return a blank white client area
+even while the app is running and rendering normally, because the capture cannot read
+the composited surface of the `QOpenGLWidget`-backed window. A blank capture therefore
+says nothing about whether the UI works, so do not read one as a regression and do not
+try to work around it. To check a UI change: build, run the tests, launch the app, and
+ask the user to look at it. Redirecting the process's stdout/stderr to a file does
+work and is worth checking for Qt warnings.
+
 ## Tests
 
 Catch2, single executable, links `lib` only — no QApplication, no display.

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}]
@@ -90,7 +94,7 @@ duration_seconds = 1.0
 # -----------------------------------------------------------------------------
 
 [[recipe]]
-id = "reprocessing_cycle"
+id = "scrap_reprocessing"
 building = "reprocessing_plant"
 inputs = [{item = "scrap", amount = 4}]
 duration_seconds = 4.0
@@ -120,21 +124,21 @@ duration_seconds = 4.0
 # -----------------------------------------------------------------------------
 
 [[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 +149,7 @@ 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 +161,14 @@ 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 +177,21 @@ 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 +206,14 @@ 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 +227,26 @@ 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 +257,35 @@ 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 +296,7 @@ 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 +307,7 @@ 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 +318,7 @@ 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 +333,21 @@ 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 +355,56 @@ 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 +415,7 @@ 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 +426,7 @@ 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 +437,7 @@ 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
@@ -348,7 +348,7 @@ deconstruct_tint  = "#ff000033"   # deconstruct-mode hover tint
 selection_rect = "#00ff00"     # box-drag selection rectangle (REQ-UI-MULTI-SELECT)
 tile_highlight = "#ffffff22"   # tile under cursor
 selected_outline = "#ffff00"   # outline drawn around currently-selected building(s)
-copy_config    = "#33ccff66"   # copy-settings eligible-target tint + copy/paste flash (REQ-BLD-COPY-CONFIG-FEEDBACK)
+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)
 tunnel_preview = "#00ff0055"   # tunnel connection preview: matched end + tiles between (REQ-BLD-TUNNEL-MODE)

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

docs/architecture.md

@@ -95,7 +95,7 @@ Schematic drops: when an enemy station set is destroyed, the simulation generate
 
 All UI interactions — building selection, builder/blueprint mode transitions, speed changes, deconstruct mode, escape menu, layout dialog requests — are communicated via EventManager events rather than Qt signals/slots. Each event is a small struct inheriting `Event` (e.g., `SelectionChangedEvent`, `BuildingTypeSelectedEvent`, `SpeedChangeRequestedEvent`). Widgets register as `CombinedEventHandler` for the events they care about and emit events via `EventManager::sendEventImmediately()`.
 
-Bidirectional interactions use separate request/notification event types to avoid infinite recursion (e.g., `ExitBuilderModeRequestedEvent` from `BuildButtonGrid` → `GameWorldView`, vs. `BuilderModeExitedEvent` from `GameWorldView` → `BuildButtonGrid`).
+Bidirectional interactions use separate request/notification event types to avoid infinite recursion (e.g., `ExitBuilderModeRequestedEvent` from `BuildButtonBar` → `GameWorldView`, vs. `BuilderModeExitedEvent` from `GameWorldView` → `BuildButtonBar`).
 
 ### Reading Simulation State
 
@@ -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 grid. 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.
@@ -333,7 +352,7 @@ The game world is drawn into a single `GameWorldView` widget that inherits `QOpe
 
 The drawing itself lives in `WorldRenderer`, not in the widget. `paintGL` is a call sequence: build the frame's `WorldCoordinates`, hand the renderer a `WorldRenderFrame`, then draw the screen-anchored chrome. The split is the world-space / screen-space line, and it is exact: the renderer draws everything positioned in tiles, while everything positioned in pixels — the pause and deconstruct vignettes, the replay overlay, the debug stats panel — stays with the widget. A useful consequence is that the renderer draws no translatable text at all (its text is config-driven glyphs, ASCII port arrows, and numbers), so it needs no `tr()` and no tie to the meta-object system.
 
-`WorldRenderFrame` is what makes the renderer independent of the widget. The renderer reads the simulation directly, but everything else it draws is interaction state the widget owns — the selection, the active build mode, live beams, the copy-settings feedback, the box-select rectangle. Those are gathered into the frame each `paintGL` and passed by reference, so the renderer keeps no copy that a later click could invalidate. The renderer knows nothing about input: the widget resolves clicks and hit-tests, and the renderer only draws the result.
+`WorldRenderFrame` is what makes the renderer independent of the widget. The renderer reads the simulation directly, but everything else it draws is interaction state the widget owns — the selection, the active build mode, live beams, the box-select rectangle. Those are gathered into the frame each `paintGL` and passed by reference, so the renderer keeps no copy that a later click could invalidate. The renderer knows nothing about input: the widget resolves clicks and hit-tests, and the renderer only draws the result.
 
 ### Render Loop
 

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/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, 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).- **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`.
@@ -127,15 +126,15 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 - 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-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, 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.
-- REQ-BLD-ROTATE-IN-PLACE: If the ghost's footprint exactly coincides with the footprint of an existing placed building or construction site of the same building type, clicking places no new construction site and consumes no building blocks. Instead, the existing building or site is rotated to match the ghost's rotation. If the target is a construction site, its construction progress is preserved. **Exception:** Tunnel Entries and Tunnel Exits are never rotated in place — re-orienting a tunnel requires deconstructing and re-placing it (REQ-BLD-TUNNEL-MODE). A tunnel ghost whose footprint coincides with an existing tunnel is therefore treated as an ordinary occupied-tile placement (invalid in normal builder mode; skipped in blueprint placement mode). This applies in both normal builder mode and blueprint placement mode; in blueprint placement mode it is evaluated per building in the blueprint independently — buildings in the blueprint whose footprint coincides with an existing same-type building or site are rotated in place, while the remaining buildings in the blueprint are placed as normal construction sites (subject to the usual validity checks and total cost).
+- 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.
+- REQ-BLD-ROTATE-IN-PLACE: If the ghost's footprint exactly coincides with the footprint of an existing placed building or construction site of the same building type, clicking places no new construction site and consumes no building blocks. Instead, the existing building or site is rotated to match the ghost's rotation. If the target is a construction site, its construction progress is preserved. **Exception:** Tunnel Entries and Tunnel Exits are never rotated in place — re-orienting a tunnel requires deconstructing and re-placing it (REQ-BLD-TUNNEL-MODE). A tunnel ghost whose footprint coincides with an existing tunnel is therefore treated as an ordinary occupied-tile placement, which is invalid. This applies **only in normal builder mode**, including the belt drag of REQ-BLD-BELT-DRAG. Blueprint placement mode never rotates an existing building in place: there, a ghost whose footprint coincides with an existing same-type building or site is a configuration-transfer target (REQ-UI-BLUEPRINT-TRANSFER), or a compatible overlap that is left untouched (REQ-UI-BLUEPRINT-OVERLAP), or else an ordinary occupied-tile overlap, which is invalid.
 - REQ-BLD-BELT-DRAG: **Belt drag placement.** For belts, placement is a deferred drag gesture rather than immediate per-tile placement: construction sites are not placed while the cursor hovers new tiles, but only once the player releases the left mouse button. Pressing the left mouse button in the game world while in belt builder mode starts a drag anchored at the tile under the cursor. As the cursor moves, a **rectilinear (L-shaped) path** of belt tiles is computed from the anchor tile to the tile under the cursor: the path first runs along the axis **parallel to the belt's current orientation** (REQ-BLD-ROTATE) — stepping toward the cursor's coordinate on that axis to a corner tile — and then runs along the orthogonal axis to the cursor tile. When the cursor shares the anchor's row or column the path degenerates to a straight line, and when it is on the anchor tile the path is a single tile.
   - **Snapping to a building.** When the tile under the cursor is occupied by a non-belt building or construction site (the **target**), the path does not end on that occupied tile. Instead the end tile is the tile **closest to the cursor** (by distance from the cursor position to the tile) among the tiles orthogonally adjacent to the target across one of its **input-capable edges** — any footprint edge that is not one of the target's output ports, i.e. an edge on which the target can accept an incoming item (REQ-MAT-INPUT-PORTS for buildings, REQ-MAT-ACCEPT-DIR for splitters and tunnels). The geometrically closest such tile is **always** used, even if it turns out not to be a valid belt endpoint — in that case it is previewed and applied by the ordinary rules below (invalid color and skipped if occupied by a non-belt building or invalid terrain; re-oriented if it already holds a belt). The rest of the L-shaped path is computed from the anchor to this end tile exactly as above. The end tile's belt direction points **toward the target** (across the shared input edge), overriding the "final tile keeps its incoming step" rule; this applies whether the end tile is a newly placed belt or an existing belt re-oriented in place, and is reflected both in the ghost preview and in the placement on release.
   - **Rotating during the drag.** Rotating the belt with R / Shift+R (REQ-BLD-ROTATE) while a drag is in progress re-picks the path's primary axis immediately from the new orientation and re-derives the whole path from the anchor to the current cursor tile, without waiting for the next cursor movement.
   - **Ghosts.** While dragging, a belt ghost (REQ-BLD-GHOST) is rendered on every path tile that would be acted on, instead of a single ghost under the cursor. Each ghost is oriented to point toward the next tile along the path toward the cursor, so the path forms one connected belt run that turns at the corner (curved belts along the path auto-derive per REQ-BLD-BELT); the final tile keeps the direction of its incoming step (unless the end tile is snapped to a building, in which case it points into the target — see **Snapping to a building**), and a single-tile path keeps the belt's current orientation. A tile occupied by only an existing belt or belt construction site is a valid target — its belt is re-oriented to follow the path — and shows a normal belt ghost. A tile occupied by a non-belt building or construction site, or otherwise an invalid belt position (REQ-BLD-PLACE-VALID), is drawn in the distinct invalid color, overriding the belt coloring. A tile whose new belt is unaffordable — the cumulative cost of the belts newly placed up to and including it exceeds the global stock — shows **no ghost at all**.
   - **Placement on release.** No construction site is placed while dragging. On releasing the left mouse button, the path is applied in order (anchor to cursor): each cell occupied by only an existing belt or belt construction site has that belt re-oriented in place to its path direction, consuming no building blocks and preserving any construction progress (REQ-BLD-ROTATE-IN-PLACE); each empty, valid cell gets a new belt construction site, consuming building blocks from the global stock (REQ-BLD-COST). Cells occupied by a non-belt building or construction site, cells that are otherwise invalid (REQ-BLD-PLACE-VALID), and cells whose new belt can no longer be afforded once the running total has been spent are skipped. This supersedes the click-to-place of REQ-BLD-PLACE for belts, including both the single-tile case and multi-tile drags that pass over existing belts.
   - **Right-click cancels the drag.** Right-clicking while a belt drag is in progress cancels it: the path is discarded, no construction site is placed, and belt builder mode stays active (the exception to REQ-BLD-BUILDER-MODE). Right-clicking when no drag is in progress exits builder mode as usual (REQ-BLD-BUILDER-MODE).
-- REQ-BLD-TUNNEL-MODE: **Unified tunnel build mode.** The build button grid contains a single **Tunnel** button rather than separate Tunnel Entry and Tunnel Exit buttons (REQ-UI-BUILD-GRID), activated by that button or by hotkey 3 (REQ-UI-HOTKEYS). This one builder mode places either a Tunnel Entry or a Tunnel Exit construction site depending on the hovered position, so the player never manually chooses between the two ends. Both remain distinct building types (REQ-BLD-TUNNEL-ENTRY, REQ-BLD-TUNNEL-EXIT) with their own costs and construction; only their build-menu entry point is unified.
+- REQ-BLD-TUNNEL-MODE: **Unified tunnel build mode.** The build button bar contains a single **Tunnel** button rather than separate Tunnel Entry and Tunnel Exit buttons (REQ-UI-BUILD-BAR), activated by that button or by hotkey 3 (REQ-UI-HOTKEYS). This one builder mode places either a Tunnel Entry or a Tunnel Exit construction site depending on the hovered position, so the player never manually chooses between the two ends. Both remain distinct building types (REQ-BLD-TUNNEL-ENTRY, REQ-BLD-TUNNEL-EXIT) with their own costs and construction; only their build-menu entry point is unified.
   - **Default type.** The ghost (REQ-BLD-GHOST) is a **Tunnel Entry** by default; clicking places a Tunnel Entry construction site (REQ-BLD-PLACE). Rotation (REQ-BLD-ROTATE) sets the ghost's facing direction as for any building.
   - **Exit-completion match.** While the ghost is at a valid position, the game tests whether placing a **Tunnel Exit** at the hovered tile with the current ghost rotation would pair — per the pairing rules of REQ-BLD-TUNNEL-PAIR (same facing direction, within `tunnel_max_distance`, first same-direction building along the search, nearest-claim semantics) — with an existing Tunnel Entry. If so, that Entry is the **exit-completion match** and the ghost turns into a **Tunnel Exit**; clicking then places a Tunnel Exit construction site.
   - **Entry-completion match.** The game also tests whether placing a **Tunnel Entry** at the hovered tile with the current ghost rotation would pair — again per REQ-BLD-TUNNEL-PAIR — with an existing Tunnel Exit. If so, that Exit is the **entry-completion match** and the ghost stays a Tunnel Entry.
@@ -146,24 +145,22 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 - 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-COPY-CONFIG: **Copy building settings (hold Shift).** While the Shift key is held, the player can copy one building's settings onto other buildings of the same type, so several identical machines can be set up without opening each one's panel. This gesture is available only in the default selection mode; while a builder, blueprint placement, or deconstruct mode is active it is disabled, so it never clashes with placement or demolition clicks.
-  - **Shift + right-click** a building copies its current settings into a temporary cache, along with the building's type. The settings copied are whatever that building type supports: the selected recipe (Miner, Assembler), the selected schematic together with its module layout (Shipyard), or the two output filters (Splitter, REQ-BLD-SPLITTER). Copying succeeds only when there is something to copy — a Miner or Assembler with a recipe selected, a Shipyard with a schematic selected, or any Splitter (whose output filters, even when empty/accept-all, always constitute valid settings). Shift + right-clicking a configurable building with nothing yet selected, a building type that has no settings at all (Smelter, Reprocessing Plant, Salvage Bay, belt/tunnel tiles, the HQ), or empty world space, has no effect and leaves any existing cache unchanged.
-  - **Shift + left-click** a building of the **same type** as the cached one applies the cached settings to it, exactly as if the player had made that selection through the selected building panel — with the same effects as a normal selection change (buffer clearing per REQ-MAT-INPUT-BUFFER and REQ-MAT-OUTPUT-BUFFER, and, for a Shipyard, in-progress cycle cancellation per REQ-BLD-SHIPYARD). This can be repeated on any number of same-type buildings while Shift stays held. Shift + left-clicking a building of a different type than the cached one, any building while the cache is empty, or empty world space, has no effect.
-  - Both operational buildings and construction sites take part as source and target (REQ-BLD-SITE-CONFIG); settings applied to a construction site carry over unchanged when it finishes building.
-  - **Releasing Shift clears the temporary cache.** It is never persisted and does not survive Shift being released; the next copy starts fresh.
-  - Because the cached settings were already valid on a same-type source building, they remain valid and available on the target (a selected recipe/schematic stays unlocked per REQ-LOCK-UI-RECIPE and REQ-LOCK-UI-SCHEMATIC; splitter filter item types stay unlocked per REQ-LOCK-UI-SPLITTER).
+- 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-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 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-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.
-- 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-REPROCESSING: **Reprocessing Plant** (3×3): Consumes scrap per cycle and produces exactly one **kind** of higher-level intermediate product per cycle via weighted random pick, in that output's configured amount (which may be more than one item). 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). Its output side follows the general rules with no exception: one buffer per possible output item (REQ-MAT-OUTPUT-BUFFER), and a cycle starts only when every possible roll would fit (REQ-MAT-CYCLE) — which is also what denies the player a reroll by stalling the output belt. Like the Smelter it picks its recipe from the first material it is offered while none is set (REQ-BLD-AUTO-RECIPE).
+- 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 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.
@@ -194,8 +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.
@@ -204,9 +201,9 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
   - **Scope.** Direct coupling is the only case in which materials move between buildings without a belt, splitter, or tunnel (REQ-MAT-BELT-ONLY); it bridges only two buildings that are directly adjacent with meeting output/input ports. Transport tiles feeding a building (belt, splitter, or tunnel exit) continue to work through the normal pull, and a producer still hands off to a transport tile placed in the gap as before; a single such tile between two buildings is unaffected by this requirement.
 - 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.
-- 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).
-- 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.
+  - **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 **one output buffer per item its recipe can produce** — each output of a deterministic recipe, and every possible roll of a probabilistic one (REQ-BLD-REPROCESSING). Each per-material buffer holds up to twice that item's per-cycle amount, 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** output the cycle could produce must fit in that item's own output buffer (REQ-MAT-OUTPUT-BUFFER). For a deterministic recipe (b) is simply its own outputs. The Reprocessing Plant rolls its output at cycle start (weighted pick, REQ-BLD-REPROCESSING), so every possible roll must fit: the roll is committed the moment the cycle begins, and a cycle whose result could not be stored must not be started at all. Testing every possibility rather than the rolled one is what keeps a stalled output belt from biasing the distribution — with one item type's buffer full the plant stops entirely instead of going on producing only the others. On cycle start, inputs are consumed immediately and the production timer begins. On cycle completion, the (already-decided) output is deposited into its output buffer 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
@@ -311,19 +308,19 @@ 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. 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; schematic changes applied via the copy-settings gesture (REQ-BLD-COPY-CONFIG) or blueprint placement (REQ-UI-BLUEPRINT-PLACE) do **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. 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.
 
@@ -377,9 +374,9 @@ 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 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).
 
@@ -397,11 +394,11 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 
 - 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-UI-RECIPE: Locked miner ore-type recipes and assembler recipes are not shown in their respective recipe-selection dialogs (REQ-UI-SELECT-BUTTON).
+- 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).
 
-- REQ-LOCK-BUILDING: A building type granted by an unlock group (REQ-LOCK-EXPLICIT) is **locked** until that group is awarded. A locked building type has no button in the build button grid (REQ-UI-BUILD-GRID) and cannot be placed, selected as a build tool, or triggered by its build hotkey (REQ-UI-HOTKEYS); its button appears in the grid only once the building type is unlocked. Building types not granted by any unlock group are available from game start. Lock state resets on Restart (REQ-CFG-RELOAD).
+- REQ-LOCK-BUILDING: A building type granted by an unlock group (REQ-LOCK-EXPLICIT) is **locked** until that group is awarded. A locked building type has no button in the build button bar (REQ-UI-BUILD-BAR) and cannot be placed, selected as a build tool, or triggered by its build hotkey (REQ-UI-HOTKEYS); its button appears in the bar only once the building type is unlocked, at which point the bar re-centers. Building types not granted by any unlock group are available from game start. Lock state resets on Restart (REQ-CFG-RELOAD).
 
 - REQ-LOCK-UI-SPLITTER: Item types that are not implicitly unlocked are excluded from splitter filter dropdowns (REQ-BLD-SPLITTER).
 
@@ -433,26 +430,25 @@ 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) containing the three UI panels stacked vertically:
+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      |
-|                                      |  Grid        |
-|                                      +--------------+
-|                                      |  Blueprint   |
-|                                      |  Panel       |
-+--------------------------------------+--------------+
-           (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).
@@ -461,9 +457,30 @@ 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 is divided into three equal-height panels stacked top to bottom: selected building panel (top), build button grid (middle), and blueprint panel (bottom).
-- 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), and the schematic choice dialog (REQ-DEF-SCHEMATIC-DROP) — 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 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. It keeps the same small margin from the view's edges that it uses as its gap from the selection.
+  - **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 panel's margin, whenever it fits within the view there. Otherwise it goes to the **left** of the anchor rectangle by that same 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. Its bottom is limited by the lowest of: the view's bottom edge less the panel's margin; and the top edge, less that 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 view's top margin 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 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 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 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 margin from the view's edges; its bottom is limited by the top edge, less that 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 view's top margin 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. 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.
 
 ### Game World
 
@@ -475,17 +492,17 @@ 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.
@@ -497,12 +514,17 @@ The screen is divided into two columns: a main column (75% width) containing the
   - **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.)
   - **R / Shift+R** — in builder mode, rotate the ghost counter-clockwise / clockwise (REQ-BLD-ROTATE).
-  - **T** — create a temporary blueprint from the current selection and enter its placement mode (REQ-UI-BLUEPRINT-TEMP).
-  - **Escape** — opens the escape menu (REQ-UI-GAME-MENU).
+  - **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).
   - **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`.
@@ -522,24 +544,74 @@ 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-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 per possible roll.
+
+  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, each output item's icon on its colored square with its per-cycle amount, and the cycle time in seconds. 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 grid); non-player-placeable buildings (the HQ and defence stations) are excluded from the total, consistent with the blueprint total (REQ-UI-BLUEPRINT-BUTTON). 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.
+- 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 (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-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 (Miner, Assembler) 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, each output item's icon with its amount, 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, each output item's icon with its amount, 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).
@@ -547,38 +619,178 @@ 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 Grid
+### Build Button Bar
 
-- REQ-UI-BUILD-GRID: All placeable building types are shown as a flat grid of buttons with no grouping. Tunnel Entry and Tunnel Exit share a single **Tunnel** button (REQ-BLD-TUNNEL-MODE) rather than one button each.
-- REQ-UI-BUILD-COST: Each button caption shows the building name and its building block cost with the `building_block` item icon (REQ-UI-BLOCKS-ICON, REQ-UI-ITEM-ICON) in place of the trailing `Blocks` word, e.g. `Belt: 2` then a small block icon. When no icon file exists for `building_block`, the caption falls back to the text form, e.g. "Belt: 2 Blocks".
-- REQ-UI-BUILD-ICON: Each build button shows an icon alongside its caption. 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-GRID) 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 with its caption and no icon; it is not an error.
-- REQ-UI-BUILD-TOOLTIP: Each building-type button shows a hover tooltip with the descriptive text defined for that building type in `buildings.toml` (the optional per-building tooltip field). This tooltip is distinct from the recipe/schematic selection tooltip (REQ-UI-SELECT-TOOLTIP). If a building type defines no tooltip text, its button shows no 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-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 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 grid. 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, 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.
 
-### Blueprint Panel
+### Controls Panel
 
-- REQ-UI-BLUEPRINT-PANEL: The blueprint panel is shown to the right of the build button grid. It contains, from top to bottom: a "Create Blueprint" button, and a list of blueprint entries (one per saved blueprint, in creation order). The panel has no Save or Load buttons; blueprints are persisted automatically (REQ-UI-BLUEPRINT-SAVE) and restored at startup (REQ-UI-BLUEPRINT-LOAD).
+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-BLUEPRINT-CREATE: The "Create Blueprint" button is enabled only when at least one player-placeable building (i.e. a building with a button in the build button grid) is currently selected; non-player-placeable buildings (HQ, defence stations) in the selection do not count toward this condition. 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). When clicked, a modal dialog appears prompting the player to enter a name. The dialog has Confirm and Cancel buttons. Clicking Cancel closes the dialog with no effect. Clicking Confirm with a non-empty name creates a blueprint from the current selection, silently excluding any non-player-placeable buildings, and appends its button to the blueprint list.
+- 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 leaves the current mode is drawn with the destructive badge styling, distinguishing it from the rows that act within the mode. 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).
 
-- REQ-UI-BLUEPRINT-TEMP: Pressing the **T** 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 T with an empty selection, or a selection containing only non-player-placeable buildings (HQ, defence stations), does nothing. 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 panel (REQ-UI-BLUEPRINT-PANEL), 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, at which point the temporary blueprint is discarded.
+  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 building type's name |
+  | 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.
+
+  **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 |
+  | | `Q` | Deconstruct mode |
+  | | `C` | Copy to temporary blueprint |
+  | | `Ctrl` `C` | Create blueprint |
+  | 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.
+  - **`C` and `Ctrl` `C`** are omitted from the Build, Blueprint, and Deconstruct contexts even though a selection surviving into a build mode keeps them working. They belong to the Selection context, and repeating them in every mode would defeat the panel's purpose of showing what the player's current situation affords.
+  - **`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). 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.
+
+- REQ-UI-BLUEPRINT-DIALOG: The **blueprint selection dialog** is the only place saved blueprints are shown. It is opened by pressing **Ctrl+V** (REQ-UI-HOTKEYS) and by confirming a save (REQ-UI-BLUEPRINT-CREATE). It is modal, pauses the simulation, and dims the game window (REQ-UI-MODAL-DIM). The dialog has a fixed size and consists of:
+  - A **title bar** reading `Blueprints`, followed by a small dimmed **hotkey badge** reading `Ctrl+V` — the same "learn the shortcut from the widget" device as the build button badges (REQ-UI-BUILD-COST) — and, at the far right, a **close ("×") button**.
+  - 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).
+
+```
++------------------------------------------------------+
+| Blueprints  [Ctrl+V]                             [x]  |
++------------------------------------------------------+
+| +---------------------+  +---------------------+ |^| |
+| | Smelter array       |  | Gear cell           | | | |
+| | 4 Smelters, 1 Miner |  | 2 Assemblers, ...   | | | |
+| | 528 [blk]       (x) |  | 460 [blk]       (x) | | | |
+| +---------------------+  +---------------------+ | | |
+| +---------------------+                          | | |
+| | Defence line        |                          |_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. 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.
+
+  There is at most one temporary blueprint at a time; pressing C replaces the previous one. It is held only in memory for the current run: it is discarded when the application closes and when the simulation is restarted from the escape menu (REQ-UI-GAME-MENU), after which V does nothing until C captures a new one.
 
 - REQ-UI-BLUEPRINT-STORAGE: A blueprint stores its name and, for each building in the selection, the building type, its rotation, its tile offset (integer dx, dy) from the center of the bounding box of all selected buildings' footprints, and — where applicable — the selected recipe ID (miners and assemblers) or schematic ID (shipyards), and for splitters the two output filters (each a list of item types; an empty list means accept-all), at the time of capture. A source building may be either an operational building or a construction site (REQ-BLD-SITE-CONFIG); a construction site is captured identically, storing whatever configuration it currently holds and never any buffer or construction-progress state. If no recipe or schematic was selected at capture time, none is stored; for a splitter with no filters set, no filter lists are stored. This structure maps directly to a TOML representation (e.g. one `[[building]]` array entry per constituent building, with the splitter filters as `filter_a`/`filter_b` arrays of item-type ids).
 
-- REQ-UI-BLUEPRINT-BUTTON: Each blueprint entry consists of a blueprint button and a dedicated delete icon ("×") placed to the right of the button. The blueprint button displays the blueprint name and, below it, the total building block cost of the blueprint (sum of the individual costs of all constituent buildings). A blueprint button is disabled when the player cannot afford the total cost. Clicking an enabled blueprint button enters blueprint placement mode for that blueprint. The delete icon is always enabled regardless of whether the player can afford the blueprint.
+- REQ-UI-BLUEPRINT-CARD: Each blueprint in the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG) is shown as a **card**. All cards share a uniform size. A card contains, from top to bottom:
+  - The **blueprint name**.
+  - A **contents line** summarizing what the blueprint holds: one `<building name> x <count>` entry per building type it contains, comma-separated, in descending count order with ties broken by the order the types appear in the build button bar (REQ-UI-BUILD-BAR). This is the same `x`-count notation as the building multi-selection summary (REQ-UI-MULTI-SELECTION). If the entries do not fit on the line, the line is elided at its end rather than wrapped or shrunk, so every card keeps the same height.
+  - The **total building block cost** of the blueprint (sum of the individual costs of all constituent buildings), shown with the `building_block` item icon to the right of the number in place of a trailing `Blocks` word, exactly as elsewhere in the UI (REQ-UI-BLOCKS-ICON, REQ-UI-BUILD-COST). When no icon file exists for `building_block`, the cost is shown as the bare number.
+  - A **delete icon ("×")** in the card's bottom-right corner (REQ-UI-BLUEPRINT-DELETE).
 
-- REQ-UI-BLUEPRINT-MODE: In blueprint placement mode a ghost is rendered for every building in the blueprint (excluding any of a currently locked building type, REQ-LOCK-BUILDING, which is omitted entirely per REQ-LOCK-UI-BLUEPRINT) at the position determined by its stored tile offset from the bounding-box center, which is anchored to the tile under the cursor. Each ghost is rendered individually as valid or invalid, applying REQ-BLD-PLACE-VALID conditions (a) and (b) per building (the other ghosts in the same blueprint do not count as existing buildings for the overlap check). A valid ghost uses its building type's semi-transparent per-building coloring (REQ-BLD-GHOST); an invalid ghost uses the distinct "invalid" color, as in single-building builder mode. Pressing R / Shift+R rotates the entire constellation 90° counter-clockwise / clockwise: each building's tile offset is rotated around the bounding-box center and each building's own rotation is updated, consistent with REQ-BLD-ROTATE. Blueprint placement mode is exited by right-clicking in the game world. Clicking a different blueprint button exits the current mode and enters blueprint placement mode for the newly clicked blueprint.
+  A card shows no preview of the blueprint's layout.
 
-- REQ-UI-BLUEPRINT-PLACE: Buildings of a currently locked building type (REQ-LOCK-BUILDING) are first excluded from the blueprint for this placement, per REQ-LOCK-UI-BLUEPRINT — they are not ghosted, not validity-checked, not placed, and their cost is excluded from the total. Left-clicking in blueprint placement mode then places the (remaining) blueprint if (a) every building in the constellation satisfies REQ-BLD-PLACE-VALID conditions (a) and (b) at its resolved tile, and (b) the player has enough building blocks to afford the total cost. If both conditions are met, a construction site is added to the build queue for each building in the blueprint and the full total cost is deducted from the global building blocks stock in one transaction. If a recipe ID is stored for a building, it is applied to the construction site immediately. If a schematic ID is stored, it is applied only if that schematic is currently unlocked; if it is not unlocked, the shipyard's schematic is left unset. If splitter output filters are stored, they are applied to the construction site immediately and carry over when it finishes building (REQ-BLD-SITE-CONFIG). Locked recipe IDs and splitter filter entries for locked item types are handled on placement per REQ-LOCK-UI-BLUEPRINT. After a successful placement the game remains in blueprint placement mode, allowing the player to place the same blueprint again immediately.
+  Clicking anywhere on an enabled card other than its delete icon closes the dialog and enters blueprint placement mode for that blueprint (REQ-UI-BLUEPRINT-MODE). A card is disabled when the player cannot currently afford its total cost; a disabled card is rendered dimmed and clicking it does nothing (consistent with REQ-UI-BUILD-DISABLED), and neither closes the dialog nor enters placement mode. The delete icon is always enabled regardless of whether the player can afford the blueprint.
 
-- REQ-UI-BLUEPRINT-DELETE: Clicking the delete icon ("×") on a blueprint entry immediately removes that blueprint from the list. If the deleted blueprint was active in blueprint placement mode, that mode is exited.
+- REQ-UI-BLUEPRINT-MODE: In blueprint placement mode a ghost is rendered for every building in the blueprint (excluding any of a currently locked building type, REQ-LOCK-BUILDING, which is omitted entirely per REQ-LOCK-UI-BLUEPRINT) at the position determined by its stored tile offset from the bounding-box center, which is anchored to the tile under the cursor. Each ghost is rendered individually as valid or invalid, applying REQ-BLD-PLACE-VALID conditions (a) and (b) per building (the other ghosts in the same blueprint do not count as existing buildings for the overlap check). A valid ghost uses its building type's semi-transparent per-building coloring (REQ-BLD-GHOST); an invalid ghost uses the distinct "invalid" color, as in single-building builder mode; a ghost over a configuration-transfer target uses the distinct "transfer" color instead of either and, for a single-building blueprint, is drawn snapped onto the target rather than at the blueprint's own position (REQ-UI-BLUEPRINT-TRANSFER); a ghost over a compatible overlap counts as valid and keeps the ordinary per-building coloring (REQ-UI-BLUEPRINT-OVERLAP). Pressing R / Shift+R rotates the entire constellation 90° counter-clockwise / clockwise: each building's tile offset is rotated around the bounding-box center and each building's own rotation is updated, consistent with REQ-BLD-ROTATE. Blueprint placement mode is exited by right-clicking in the game world. Opening the blueprint selection dialog while placement mode is active (REQ-UI-BLUEPRINT-DIALOG) leaves the mode active — closing the dialog without picking a card returns to it unchanged — while clicking a card exits the current mode and enters blueprint placement mode for the newly picked blueprint.
+
+- REQ-UI-BLUEPRINT-PLACE: This describes placing the blueprint's buildings as new construction sites. Ghosts sitting on a building that is already there are handled elsewhere and place nothing: a configuration-transfer target receives the blueprint's stored settings instead (REQ-UI-BLUEPRINT-TRANSFER), and a compatible overlap is left alone (REQ-UI-BLUEPRINT-OVERLAP). Both still take part in the single all-or-nothing click described here. Buildings of a currently locked building type (REQ-LOCK-BUILDING) are first excluded from the blueprint for this placement, per REQ-LOCK-UI-BLUEPRINT — they are not ghosted, not validity-checked, not placed, and their cost is excluded from the total. Left-clicking in blueprint placement mode then places the (remaining) blueprint if (a) every building in the constellation satisfies REQ-BLD-PLACE-VALID conditions (a) and (b) at its resolved tile, and (b) the player has enough building blocks to afford the total cost. Buildings that are compatible overlaps (REQ-UI-BLUEPRINT-OVERLAP) or configuration-transfer targets (REQ-UI-BLUEPRINT-TRANSFER) are excluded from the total cost and are not placed, but do not block the placement; a transfer target additionally receives the blueprint's stored settings. If both conditions are met, a construction site is added to the build queue for each remaining building in the blueprint and the full total cost is deducted from the global building blocks stock in one transaction. If a recipe ID is stored for a building, it is applied to the construction site immediately. If a schematic ID is stored, it is applied only if that schematic is currently unlocked; if it is not unlocked, the shipyard's schematic is left unset. If splitter output filters are stored, they are applied to the construction site immediately and carry over when it finishes building (REQ-BLD-SITE-CONFIG). Locked recipe IDs and splitter filter entries for locked item types are handled on placement per REQ-LOCK-UI-BLUEPRINT. After a successful placement the game remains in blueprint placement mode, allowing the player to place the same blueprint again immediately.
+
+- REQ-UI-BLUEPRINT-OVERLAP: **Compatible overlap.** In blueprint placement mode, a ghost whose footprint **exactly coincides** with the footprint of an existing placed building or construction site that is of the **same building type** and has the **same rotation** is a *compatible overlap*: the building the blueprint wants is already there. Such a ghost is **valid** despite the occupied tiles (REQ-BLD-PLACE-VALID condition (b)), so it does not block the placement of the rest of the constellation — dropping a blueprint over a partially-built copy of itself fills in what is missing. It is drawn in the ordinary per-building ghost color (REQ-BLD-GHOST), like any other valid ghost.
+
+  On placement the overlapped building is **left completely untouched**: no construction site is placed on it, no building blocks are charged for it (it is excluded from the total cost of REQ-UI-BLUEPRINT-PLACE), its rotation is not changed, and a construction site's progress is preserved. This applies per building in the blueprint, independently, and to blueprints of any size. Unlike REQ-BLD-ROTATE-IN-PLACE, which it replaces in this mode, it applies to Tunnel Entries and Tunnel Exits too — nothing is re-oriented, so the reason for their exception does not arise.
+
+  A coinciding same-type building whose **rotation differs** is not a compatible overlap: the blueprint cannot rotate it (REQ-BLD-ROTATE-IN-PLACE no longer applies here), so the position is an ordinary occupied-tile overlap and therefore invalid.
+
+  **Order of the two rules.** A ghost is tested for a configuration transfer (REQ-UI-BLUEPRINT-TRANSFER) first, and this requirement governs only what that test does not claim. Because a coinciding building of a **configurable** type always transfers, this requirement covers exactly the types that have nothing to configure:
+  - **Configurable type** (Miner, Assembler, Shipyard, Splitter) — a transfer, never a compatible overlap. It is drawn in the transfer color and hands the blueprint's settings over.
+  - **Type with no settings** (Smelter, Reprocessing Plant, Salvage Bay, belt, tunnel end) — a compatible overlap if the rotation matches, invalid otherwise. There is nothing to hand over, so the building is simply left as it is and the ghost keeps its ordinary color. This holds for a single-building blueprint too: the cursor hit-test of REQ-UI-BLUEPRINT-TRANSFER applies only to configurable types, so hovering a belt with a belt blueprint still just overlaps it.
+
+  A single blueprint can hold both kinds at once, and each ghost is judged on its own: dropping a constellation over a partial copy of itself may reconfigure some of the buildings already there (cyan) while leaving others untouched (ordinary color) and placing the rest as new construction sites.
+
+- REQ-UI-BLUEPRINT-TRANSFER: **Configuration transfer.** A blueprint hands its stored settings to buildings that are already standing where it wants them, instead of only to ones it places. A single-building blueprint therefore doubles as a way to copy one building's settings onto others of the same type: select a configured building, press **C** to capture it as a temporary blueprint and enter placement mode (REQ-UI-BLUEPRINT-TEMP), then click same-type buildings to stamp its settings onto them. **V** re-enters that mode later. A multi-building blueprint does the same for each of its buildings as it is placed.
+
+  A blueprint ghost is a **configuration-transfer target** when all of the following hold:
+  - The building is of a **configurable building type** — one with player-facing settings: Miner and Assembler (recipe), Shipyard (schematic and module layout), Splitter (output filters). Whether anything was actually configured at capture time is irrelevant; an unconfigured source transfers its unconfigured state (see below). Building types with no settings at all (Smelter, Reprocessing Plant, Salvage Bay, belts, tunnel entries and exits, the HQ) never transfer; a coinciding building of those types is a compatible overlap instead (REQ-UI-BLUEPRINT-OVERLAP).
+  - There is a target, found in one of two ways depending on the blueprint's size, because the two are different gestures:
+    - **Single-building blueprint** — the target is the building or construction site **under the cursor**, if it is of the same type. There is no coincidence test at all: the target's rotation, its footprint, and its alignment with the ghost are all irrelevant. The ghost is drawn **snapped onto the target**, at the target's own anchor and rotation, so it shows what the click will act on rather than where a building would go. This is the copying gesture, and a footprint test made it unusable for buildings that are not square: a Shipyard rotated 90° covers different tiles altogether, so no amount of lining up would ever match a differently-facing one.
+    - **Multi-building blueprint** — the ghost's footprint must **exactly coincide** with the footprint of an existing building or site of the same type (the coincidence test of REQ-BLD-ROTATE-IN-PLACE), and that target must have the **same rotation** as the ghost, which is what makes the position valid at all (REQ-UI-BLUEPRINT-OVERLAP). A constellation is placed as a layout, so its ghosts stay where the blueprint puts them: nothing snaps to the cursor and nothing is re-oriented.
+
+  At a transfer target:
+  - 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 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.
+  - A blueprint placement applies every transfer among its ghosts in the same click that places its new construction sites (REQ-UI-BLUEPRINT-PLACE); the placement is all-or-nothing, so if any ghost is invalid nothing is placed and nothing is transferred.
+
+- REQ-UI-BLUEPRINT-DELETE: Clicking the delete icon ("×") on a blueprint card (REQ-UI-BLUEPRINT-CARD) immediately removes that blueprint from the list, without a confirmation prompt. The blueprint selection dialog stays open and its card grid reflows to close the gap. If the deleted blueprint was active in blueprint placement mode, that mode is exited.
 
 - REQ-UI-BLUEPRINT-SAVE: On application shutdown, all current blueprints are serialized to a file named `blueprints.toml` located in the same directory as the application executable. The TOML structure matches REQ-UI-BLUEPRINT-STORAGE. Write errors are silently ignored on shutdown (no button, no dialog).
 

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

@@ -94,14 +94,6 @@ RecipesConfig ConfigLoader::loadRecipes(const std::string& path)
         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"))
-        {
-            def.icon = utility::requireString(mt["icon"], file, elemPath + ".icon");
-        }
-
         cfg.recipes.push_back(std::move(def));
     }
 

src/lib/config/RecipesConfig.h

@@ -32,10 +32,6 @@ struct RecipeDef
     std::vector<RecipeIngredient> inputs;
     std::vector<RecipeOutput> outputs;
     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.

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;
@@ -249,6 +250,16 @@ 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

@@ -95,6 +95,15 @@ public:
     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);
@@ -118,6 +127,7 @@ private:
 
     Blueprint m_blueprint;
     QPoint    m_blueprintGhostTile;
+    bool      m_hoveredGhostIsTransfer = false;
 
     std::optional<BuildingId> m_deconstructHoverBuildingId;
 };

src/lib/core/BuildingType.cpp

@@ -53,6 +53,22 @@ bool isBeltSubsystemType(BuildingType type)
         || type == BuildingType::TunnelExit;
 }
 
+bool isConfigurableBuildingType(BuildingType type)
+{
+    switch (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;
+    default:
+        return false;
+    }
+}
+
 bool isProductionBuildingType(BuildingType type)
 {
     switch (type)

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
@@ -43,3 +43,11 @@ bool isProductionBuildingType(BuildingType type);
 // rather than in the Building instance, so placing/removing them must register or
 // unregister a tile with BeltSystem.
 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, 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 +16,10 @@ 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}/SelectionController.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildModeController.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlAction.h
     PARENT_SCOPE
 )
 
@@ -31,8 +33,10 @@ 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 +1,263 @@
+#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.
+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::EnterDeconstruct, Qt::Key_Q,      Qt::NoModifier},
+    {ControlAction::ExitMode,         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:
+    case ControlAction::EnterDeconstruct:
+        return context.mode == BuildMode::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);
+    case ControlContextKind::Selection:
+        return filterAvailable({ControlAction::Select, ControlAction::SelectArea,
+                                ControlAction::AddToSelection,
+                                ControlAction::AddAreaToSelection,
+                                ControlAction::EnterDeconstruct,
+                                ControlAction::CopyTemporary,
+                                ControlAction::CreateBlueprint},
+                               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 +1,164 @@
+#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,
+
+    // 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;
+    BuildingType     builderType               = BuildingType::Belt;  // while mode == Builder
+    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 +1,110 @@
+#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 marginPx)
+{
+    // What each side offers: the gap between the anchor and that edge of the band, less
+    // the margin the panel keeps from the anchor.
+    const int roomRightPx = band.right() - anchorRect.right() - marginPx;
+    const int roomLeftPx  = anchorRect.left() - band.left() - marginPx;
+
+    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 marginPx)
+{
+    const int widthPx = std::min(wantedSize.width(), band.width());
+
+    // Against 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() + marginPx + 1
+                                 : anchorRect.left() - marginPx - widthPx;
+
+    // Top-aligned with the anchor, then lifted by however much of it 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 +1,54 @@
+#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.
+
+// 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). 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 marginPx);
+
+// Where a panel of wantedSize stands beside anchorRect on the given side: separated from
+// it by marginPx and growing away from it, its top edge on the anchor's top edge, pushed
+// inside band and above whatever occupies it. 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 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/eventsystem/event/BlueprintSaveRequestedEvent.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include "Event.h"
+
+// Ctrl+C: save the current building selection as a named blueprint
+// (REQ-UI-BLUEPRINT-CREATE, REQ-UI-HOTKEYS). MainWindow owns the modal flow, because
+// it is the only widget that can pause the game and raise the dim overlay; whether
+// anything placeable is selected is decided there, not by the key handler.
+class BlueprintSaveRequestedEvent : public Event
+{
+};

src/lib/eventsystem/event/BlueprintSelectionRequestedEvent.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include "Event.h"
+
+// Ctrl+V: open the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG,
+// REQ-UI-HOTKEYS). The Ctrl+C path does not go through this event -- it opens the
+// dialog directly so one pause scope and one dim scope span both dialogs
+// (REQ-UI-MODAL-DIM).
+class BlueprintSelectionRequestedEvent : public Event
+{
+};

src/lib/eventsystem/event/CMakeLists.txt

@@ -9,12 +9,16 @@ 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
 	${CMAKE_CURRENT_SOURCE_DIR}/ArtifactCountChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/UnlockedBuildingsChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BuilderModeExitedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BlueprintModeExitedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSaveRequestedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSelectionRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/EscapeMenuRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/PanDirectionChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/PauseToggleRequestedEvent.h
@@ -29,7 +33,8 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/DeconstructModeToggleRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BlueprintPlacementRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/ExitBlueprintModeRequestedEvent.h
-	${CMAKE_CURRENT_SOURCE_DIR}/TemporaryBlueprintRequestedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/TemporaryBlueprintCaptureRequestedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/TemporaryBlueprintPlaceRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/SpeedChangeRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/LayoutDialogRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/RecipeSelectionRequestedEvent.h
@@ -39,6 +44,7 @@ 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/GameResetEvent.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include "Event.h"
+
+// Emitted once per restart, after a queued ResetCommand has been applied and the view has
+// been reset for the new run (REQ-UI-GAME-MENU). It lets presentation state that does not
+// live in the simulation -- e.g. the temporary blueprint, REQ-UI-BLUEPRINT-TEMP -- be
+// dropped for the fresh run. Sent from GameWorldView::resetForNewGame(), which is where a
+// restart actually lands: the escape menu, game over, and win dialogs only enqueue the
+// command.
+class GameResetEvent : public Event
+{
+};

src/lib/eventsystem/event/SelectionAnchorChangedEvent.h

@@ -0,0 +1,25 @@
+#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.
+class SelectionAnchorChangedEvent : public Event
+{
+public:
+    explicit SelectionAnchorChangedEvent(QRect rectPx)
+        : rectPx(rectPx) {}
+
+    const QRect rectPx;
+};

src/lib/eventsystem/event/TemporaryBlueprintCaptureRequestedEvent.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include "Event.h"
+
+// Emitted when the player presses C to capture a temporary blueprint (REQ-UI-BLUEPRINT-TEMP).
+// Carries no payload: the blueprint is built from the current selection by the receiver.
+class TemporaryBlueprintCaptureRequestedEvent : public Event
+{
+};

src/lib/eventsystem/event/TemporaryBlueprintPlaceRequestedEvent.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "Event.h"
+
+// Emitted when the player presses V to re-enter placement mode for the temporary blueprint
+// captured with C (REQ-UI-BLUEPRINT-TEMP). Carries no payload: the receiver holds the
+// blueprint, and nothing is captured from the current selection.
+class TemporaryBlueprintPlaceRequestedEvent : public Event
+{
+};

src/lib/eventsystem/event/TemporaryBlueprintRequestedEvent.h

@@ -1,9 +0,0 @@
-#pragma once
-
-#include "Event.h"
-
-// Emitted when the player presses the temporary-blueprint hotkey (REQ-UI-BLUEPRINT-TEMP).
-// Carries no payload: the blueprint is built from the current selection by the receiver.
-class TemporaryBlueprintRequestedEvent : public Event
-{
-};

src/lib/eventsystem/event/UnlockedBuildingsChangedEvent.h

@@ -5,7 +5,7 @@
 
 // Emitted when the set of unlocked building types changes (REQ-LOCK-BUILDING),
 // i.e. after an unlock group granting a building is awarded (REQ-DEF-SCHEMATIC-DROP)
-// or on Restart. The build button grid re-evaluates which buttons are shown.
+// or on Restart. The build button bar re-evaluates which buttons are shown.
 class UnlockedBuildingsChangedEvent : 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 Reprocessing Plant rolls exactly
+// one of its outputs per cycle (REQ-BLD-REPROCESSING), so its per-cycle amount for an
+// item is that one outcome's amount rather than a sum over the entries.
+//
+// Where a cap is already present the larger wins, which is how an auto-recipe building
+// unions the recipes of its type -- the same rule its input caps follow.
+void addOutputCaps(std::map<ItemType, int>& caps, BuildingType type,
+                   const RecipeDef& recipe)
+{
+    std::map<ItemType, int> perCycle;
+    for (const RecipeOutput& out : recipe.outputs)
+    {
+        const ItemType item{out.item};
+        if (type == BuildingType::ReprocessingPlant)
+        {
+            perCycle[item] = std::max(perCycle[item], out.amount);
+        }
+        else
+        {
+            perCycle[item] += out.amount;
+        }
+    }
+
+    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, b.type, 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/BuildingConfig.cpp

@@ -3,10 +3,14 @@
 
 #include <algorithm>
 #include <climits>
+#include <cstddef>
+#include <map>
 
 #include "BeltSystem.h"
 #include "Building.h"
+#include "BuildingsConfig.h"
 #include "BuildingSystem.h"
+#include "DisplayName.h"
 #include "Simulation.h"
 
 namespace
@@ -49,6 +53,21 @@ std::optional<SelectedBuilding> resolvePlaceable(const Simulation& sim, Building
     resolved.bodyCells = building ? &building->bodyCells : &site->bodyCells;
     return resolved;
 }
+
+// Position of a building type in buildings.toml, which is the order the build button
+// bar lays out its buttons (REQ-UI-BUILD-BAR) and so the tie-break order for a
+// blueprint's contents line. A type with no config entry sorts after every known one.
+std::size_t configOrderIndex(BuildingType type, const BuildingsConfig& buildings)
+{
+    for (std::size_t i = 0; i < buildings.buildings.size(); ++i)
+    {
+        if (buildings.buildings[i].type == type)
+        {
+            return i;
+        }
+    }
+    return buildings.buildings.size();
+}
 } // namespace
 
 std::optional<BuildingConfig> readBuildingConfig(const Simulation& sim, BuildingId id)
@@ -138,9 +157,9 @@ Blueprint captureBlueprintFromSelection(const Simulation&              sim,
         building.type     = e.type;
         building.rotation = e.rotation;
         building.offset   = e.anchor - center;
-        // Recipe / schematic / layout / splitter-filter capture is shared with the
-        // copy-settings gesture (REQ-BLD-COPY-CONFIG) via readBuildingConfig, which
-        // handles operational buildings and construction sites alike.
+        // Recipe / schematic / layout / splitter-filter capture goes through
+        // readBuildingConfig, which handles operational buildings and construction
+        // sites alike.
         const std::optional<BuildingConfig> config = readBuildingConfig(sim, e.id);
         if (config.has_value())
         {
@@ -166,3 +185,56 @@ bool selectionHasPlaceableBuilding(const Simulation&              sim,
     }
     return false;
 }
+
+std::vector<BlueprintContentEntry> summarizeBlueprintContents(
+    const Blueprint& blueprint, const BuildingsConfig& buildings)
+{
+    std::map<BuildingType, int> counts;
+    for (const BlueprintBuilding& building : blueprint.buildings)
+    {
+        ++counts[building.type];
+    }
+
+    // The config index is carried through the sort so the comparator stays a strict
+    // total order; the enum value is the final tie-break, which only two config-less
+    // types could ever reach.
+    struct RankedType
+    {
+        BuildingType type;
+        int          count;
+        std::size_t  order;
+    };
+    std::vector<RankedType> ranked;
+    ranked.reserve(counts.size());
+    for (const std::pair<const BuildingType, int>& entry : counts)
+    {
+        ranked.push_back({entry.first, entry.second,
+                          configOrderIndex(entry.first, buildings)});
+    }
+    std::sort(ranked.begin(), ranked.end(),
+              [](const RankedType& left, const RankedType& right)
+    {
+        if (left.count != right.count) { return left.count > right.count; }
+        if (left.order != right.order) { return left.order < right.order; }
+        return static_cast<int>(left.type) < static_cast<int>(right.type);
+    });
+
+    std::vector<BlueprintContentEntry> summary;
+    summary.reserve(ranked.size());
+    for (const RankedType& entry : ranked)
+    {
+        summary.push_back({toDisplayName(buildingTypeId(entry.type)), entry.count});
+    }
+    return summary;
+}
+
+int computeBlueprintCost(const Blueprint& blueprint, const BuildingsConfig& buildings)
+{
+    int total = 0;
+    for (const BlueprintBuilding& building : blueprint.buildings)
+    {
+        const BuildingDef* def = buildings.findBuildingDef(building.type);
+        if (def) { total += def->cost; }
+    }
+    return total;
+}

src/lib/sim/BuildingConfig.h

@@ -11,11 +11,12 @@
 #include "ShipLayout.h"
 
 class Simulation;
+struct BuildingsConfig;
 
 // The user-configurable settings of a single building or construction site: the
 // selected recipe / ship schematic, the shipyard module layout, and (for
-// splitters) the two output filters. Shared by the copy-settings gesture
-// (REQ-BLD-COPY-CONFIG) and blueprint capture (REQ-UI-BLUEPRINT-STORAGE).
+// splitters) the two output filters. This is what blueprint capture records per
+// constituent building (REQ-UI-BLUEPRINT-STORAGE).
 struct BuildingConfig
 {
     BuildingType type = BuildingType::Miner;
@@ -49,6 +50,29 @@ Blueprint captureBlueprintFromSelection(const Simulation&              sim,
                                         const std::vector<BuildingId>& selectedIds);
 
 // True if any selected id refers to a player-placeable building or construction site
-// (the enable condition for the Create Blueprint button, REQ-UI-BLUEPRINT-CREATE).
+// (the condition under which Ctrl+C opens the blueprint save dialog,
+// REQ-UI-BLUEPRINT-CREATE).
 bool selectionHasPlaceableBuilding(const Simulation&              sim,
                                    const std::vector<BuildingId>& selectedIds);
+
+// One "<building name> x <count>" entry of a blueprint card's contents line
+// (REQ-UI-BLUEPRINT-CARD).
+struct BlueprintContentEntry
+{
+    std::string buildingName;
+    int         count;
+};
+
+// Summarizes what a blueprint holds: one entry per building type it contains, ordered
+// by descending count with ties broken by the order the types appear in buildings.toml
+// (which is the order of the build button bar, REQ-UI-BUILD-BAR). Building types absent
+// from the config sort last. Derived display data for the blueprint card, kept here so
+// it is unit-testable rather than buried in the dialog (REQ-UI-BLUEPRINT-CARD).
+std::vector<BlueprintContentEntry> summarizeBlueprintContents(
+    const Blueprint& blueprint, const BuildingsConfig& buildings);
+
+// Plain sum of the placement cost of every building in the blueprint
+// (REQ-UI-BLUEPRINT-CARD). Distinct from the total charged on placement
+// (REQ-UI-BLUEPRINT-PLACE), which additionally excludes locked building types and
+// rotate-in-place targets; see GameWorldView's placement path.
+int computeBlueprintCost(const Blueprint& blueprint, const BuildingsConfig& buildings);

src/lib/sim/BuildingSystem.cpp

@@ -200,12 +200,6 @@ 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 +217,6 @@ 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 +228,7 @@ 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
@@ -284,6 +272,21 @@ void BuildingSystem::setShipLayout(FactoryState& state, BuildingId id, const Shi
     {
         if (building.id == id)
         {
+            // No-op if the layout is unchanged, so re-applying the layout a shipyard
+            // already has does not cancel its production cycle or wipe its buffers
+            // (REQ-MAT-INPUT-BUFFER, REQ-BLD-SHIPYARD). Confirming the layout dialog
+            // without editing anything, and a blueprint configuration transfer onto an
+            // already-matching shipyard (REQ-UI-BLUEPRINT-TRANSFER), both land here.
+            // An unset layout counts as an empty one: the two are equivalent for
+            // buffers, production, and the spawned ship (see the spawn path below),
+            // so an empty layout arriving at an unconfigured shipyard changes nothing.
+            const bool unchanged = building.shipLayout.has_value()
+                                       ? *building.shipLayout == layout
+                                       : layout.placedModules.empty();
+            if (unchanged)
+            {
+                return;
+            }
             if (building.production.has_value())
             {
                 building.production = std::nullopt;
@@ -292,7 +295,7 @@ 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)
@@ -392,6 +395,10 @@ 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)
@@ -402,6 +409,25 @@ 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
@@ -462,6 +488,10 @@ 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;
@@ -487,88 +517,92 @@ 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;
-            }
+            continue;
+        }
 
-            // 2. Determine chosen outputs (roll for reprocessing).
-            std::vector<Item> chosen;
-            if (building.type == BuildingType::ReprocessingPlant)
+        // 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. 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)
             {
-                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)
                 {
-                    Item item;
-                    item.type.id = out.item;
-                    for (int i = 0; i < out.amount; ++i)
-                    {
-                        chosen.push_back(item);
-                    }
+                    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.
         }
+
+        // 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);
     }
 }
 
@@ -597,26 +631,29 @@ 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).
@@ -927,21 +964,22 @@ 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
 
@@ -961,7 +999,7 @@ 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).

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/FactoryQueries.cpp

@@ -4,6 +4,7 @@
 #include <limits>
 
 #include "PortGeometry.h"
+#include "ProductionRules.h"
 #include "SurfaceMask.h"
 
 #include "Item.h"
@@ -122,12 +123,14 @@ 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;
 }
 

src/lib/sim/PlacementRules.cpp

@@ -69,16 +69,9 @@ bool isPlacementValid(const FactoryState& state, const GameConfig& config,Buildi
 }
 
 
-std::optional<BuildingId> findRotateInPlaceTarget(const FactoryState& state, const GameConfig& config,
-    BuildingType type, QPoint anchor, Rotation rot)
+std::optional<CoincidingBuilding> findCoincidingSameTypeBuilding(const FactoryState& state,
+    const GameConfig& config, BuildingType type, QPoint anchor, Rotation rot)
 {
-    // Tunnel Entries and Tunnel Exits cannot be rotated in place; re-orienting a
-    // tunnel requires deconstructing and re-placing it (REQ-BLD-ROTATE-IN-PLACE).
-    if (type == BuildingType::TunnelEntry || type == BuildingType::TunnelExit)
-    {
-        return std::nullopt;
-    }
-
     const BuildingDef* def = config.buildings.findBuildingDef(type);
     if (!def) { return std::nullopt; }
 
@@ -106,20 +99,138 @@ std::optional<BuildingId> findRotateInPlaceTarget(const FactoryState& state, con
         if (site.id != candidateId) { continue; }
         if (site.type != type) { return std::nullopt; }
         if (site.bodyCells.size() != mask.bodyCells.size()) { return std::nullopt; }
-        return candidateId;
+        return CoincidingBuilding{candidateId, site.rotation};
     }
     for (const Building& b : state.buildings)
     {
         if (b.id != candidateId) { continue; }
         if (b.type != type) { return std::nullopt; }
         if (b.bodyCells.size() != mask.bodyCells.size()) { return std::nullopt; }
-        return candidateId;
+        return CoincidingBuilding{candidateId, b.rotation};
     }
 
     return std::nullopt;
 }
 
 
+std::optional<BuildingId> findRotateInPlaceTarget(const FactoryState& state, const GameConfig& config,
+    BuildingType type, QPoint anchor, Rotation rot)
+{
+    // Tunnel Entries and Tunnel Exits cannot be rotated in place; re-orienting a
+    // tunnel requires deconstructing and re-placing it (REQ-BLD-ROTATE-IN-PLACE).
+    if (type == BuildingType::TunnelEntry || type == BuildingType::TunnelExit)
+    {
+        return std::nullopt;
+    }
+
+    const std::optional<CoincidingBuilding> target =
+        findCoincidingSameTypeBuilding(state, config, type, anchor, rot);
+    if (!target.has_value()) { return std::nullopt; }
+    return target->id;
+}
+
+
+namespace
+{
+
+// The building or construction site occupying `tile`, if it is of `type`, together with
+// where it stands. The single-building transfer gesture hit-tests the cursor with this
+// instead of comparing footprints (REQ-UI-BLUEPRINT-TRANSFER).
+std::optional<CoincidingBuilding> findSameTypeBuildingAt(const FactoryState& state,
+                                                         BuildingType type, QPoint tile,
+                                                         QPoint& anchorOut)
+{
+    const std::optional<BuildingId> owner = state.grid.findOwner(tile);
+    if (!owner.has_value()) { return std::nullopt; }
+
+    if (const ConstructionSite* site = findSite(state, *owner))
+    {
+        if (site->type != type) { return std::nullopt; }
+        anchorOut = site->anchor;
+        return CoincidingBuilding{site->id, site->rotation};
+    }
+    if (const Building* building = findBuilding(state, *owner))
+    {
+        if (building->type != type) { return std::nullopt; }
+        anchorOut = building->anchor;
+        return CoincidingBuilding{building->id, building->rotation};
+    }
+    return std::nullopt;
+}
+
+}  // namespace
+
+
+BlueprintGhostResolved resolveBlueprintGhost(const FactoryState& state, const GameConfig& config,
+    BuildingType type, QPoint anchor, Rotation rotation, std::optional<QPoint> hoverTile)
+{
+    // The single-building gesture first, because it answers without looking at the
+    // ghost's own position at all: whatever same-type building the cursor is on takes the
+    // settings, at any facing, and the ghost snaps onto it (REQ-UI-BLUEPRINT-TRANSFER).
+    if (hoverTile.has_value() && isConfigurableBuildingType(type))
+    {
+        QPoint hoveredAnchor;
+        const std::optional<CoincidingBuilding> hovered =
+            findSameTypeBuildingAt(state, type, *hoverTile, hoveredAnchor);
+        if (hovered.has_value())
+        {
+            return BlueprintGhostResolved{BlueprintGhostAction::Transfer, hovered->id,
+                                          hoveredAnchor, hovered->rotation};
+        }
+    }
+
+    // Terrain and world bounds next: nothing rescues a ghost hanging off the asteroid
+    // (REQ-BLD-PLACE-VALID condition (a)).
+    if (!isPlacementValid(state, config, type, anchor, rotation))
+    {
+        return BlueprintGhostResolved{BlueprintGhostAction::Invalid, std::nullopt,
+                                      anchor, rotation};
+    }
+
+    const std::optional<CoincidingBuilding> coinciding =
+        findCoincidingSameTypeBuilding(state, config, type, anchor, rotation);
+    if (coinciding.has_value())
+    {
+        // The building the blueprint wants is already there, facing the same way. It
+        // takes the blueprint's settings if it has any to take (REQ-UI-BLUEPRINT-TRANSFER)
+        // and is otherwise left exactly as it is (REQ-UI-BLUEPRINT-OVERLAP). Tunnels are
+        // not excluded from the latter: nothing is rotated, so the reason for their
+        // REQ-BLD-ROTATE-IN-PLACE exception does not arise.
+        if (coinciding->rotation == rotation)
+        {
+            return BlueprintGhostResolved{isConfigurableBuildingType(type)
+                                              ? BlueprintGhostAction::Transfer
+                                              : BlueprintGhostAction::CompatibleOverlap,
+                                          coinciding->id, anchor, rotation};
+        }
+
+        // Facing the other way, and placement may not re-orient it.
+        return BlueprintGhostResolved{BlueprintGhostAction::Invalid, std::nullopt,
+                                      anchor, rotation};
+    }
+
+    // No coincidence: any occupancy at all is an ordinary overlap
+    // (REQ-BLD-PLACE-VALID condition (b)).
+    const BuildingDef* def = config.buildings.findBuildingDef(type);
+    if (!def)
+    {
+        return BlueprintGhostResolved{BlueprintGhostAction::Invalid, std::nullopt,
+                                      anchor, rotation};
+    }
+    const ParsedSurfaceMask parsed = parseSurfaceMask(def->surfaceMask, rotation);
+    for (const QPoint& relativeCell : parsed.bodyCells)
+    {
+        if (isTileOccupied(state, anchor + relativeCell))
+        {
+            return BlueprintGhostResolved{BlueprintGhostAction::Invalid, std::nullopt,
+                                          anchor, rotation};
+        }
+    }
+    return BlueprintGhostResolved{BlueprintGhostAction::PlaceNew, std::nullopt,
+                                  anchor, rotation};
+}
+
+
 bool canPlaceBuilding(const FactoryState& state, const GameConfig& config,
                       BuildingType type, QPoint anchor, Rotation rotation)
 {

src/lib/sim/PlacementRules.h

@@ -30,9 +30,27 @@ bool bodyCellsWithinWorldBounds(const FactoryState& state, const GameConfig& con
 bool isPlacementValid(const FactoryState& state, const GameConfig& config,
                       BuildingType type, QPoint anchor, Rotation rotation);
 
+// An existing building or site whose footprint a ghost exactly covers.
+struct CoincidingBuilding
+{
+    BuildingId id;
+    Rotation   rotation;
+};
+
+// The building or site whose footprint a ghost of the given type/anchor/rotation
+// exactly covers: same type, same body cells, a single owner. Operational buildings
+// and construction sites alike. Rotation is not part of the test -- the target's own
+// facing is reported so each caller can apply its own rule to it.
+std::optional<CoincidingBuilding> findCoincidingSameTypeBuilding(const FactoryState& state,
+                                                                 const GameConfig& config,
+                                                                 BuildingType type,
+                                                                 QPoint anchor,
+                                                                 Rotation rot);
+
 // The building or site that a ghost of the given type/anchor/rotation would
 // rotate in place rather than replace: same type, same body cells, one owner
-// (REQ-BLD-ROTATE-IN-PLACE). Tunnels never qualify.
+// (REQ-BLD-ROTATE-IN-PLACE). Tunnels never qualify. Builder mode only; blueprint
+// placement mode never rotates anything -- see resolveBlueprintGhost.
 std::optional<BuildingId> findRotateInPlaceTarget(const FactoryState& state,
                                                   const GameConfig& config,
                                                   BuildingType type, QPoint anchor,
@@ -46,6 +64,48 @@ std::optional<BuildingId> findRotateInPlaceTarget(const FactoryState& state,
 bool canPlaceBuilding(const FactoryState& state, const GameConfig& config,
                       BuildingType type, QPoint anchor, Rotation rotation);
 
+// What one ghost of a blueprint would do at its resolved tile.
+enum class BlueprintGhostAction
+{
+    PlaceNew,           // free, valid cells: a new construction site, charged for
+    CompatibleOverlap,  // the same building is already there: left untouched, free
+                        // (REQ-UI-BLUEPRINT-OVERLAP)
+    Transfer,           // hand this blueprint's settings to the building already there,
+                        // free (REQ-UI-BLUEPRINT-TRANSFER)
+    Invalid             // terrain, bounds, or an overlap that is neither of the above
+};
+
+struct BlueprintGhostResolved
+{
+    BlueprintGhostAction      action;
+    std::optional<BuildingId> targetId;  // set for CompatibleOverlap and Transfer
+    // Where the ghost belongs on screen. The queried anchor and rotation, except at a
+    // hovered transfer target, where the ghost snaps onto the target so it shows what the
+    // click will act on (REQ-UI-BLUEPRINT-TRANSFER).
+    QPoint                    ghostAnchor;
+    Rotation                  ghostRotation;
+};
+
+// Classifies one ghost of a blueprint against the current factory state
+// (REQ-UI-BLUEPRINT-OVERLAP, REQ-UI-BLUEPRINT-TRANSFER).
+//
+// `hoverTile` is set only for a blueprint holding exactly one building, and is then the
+// tile under the cursor. That gesture is a copying tool rather than a layout, so it finds
+// its transfer target by hit-testing the cursor instead of by footprint coincidence --
+// without which a Shipyard could never be targeted at a different facing, its 4x2
+// footprint covering entirely different tiles once rotated. Pass nullopt for a
+// constellation, whose ghosts are judged purely by where the blueprint puts them. The
+// size is read from the blueprint as stored, before locked types are dropped, so the
+// gesture does not change behavior as the player unlocks things.
+//
+// Shared by the ghost coloring and the click path so a preview cannot disagree with what
+// the click then does -- the same reason resolveBeltDragPath is shared.
+BlueprintGhostResolved resolveBlueprintGhost(const FactoryState& state,
+                                             const GameConfig& config,
+                                             BuildingType type, QPoint anchor,
+                                             Rotation rotation,
+                                             std::optional<QPoint> hoverTile);
+
 // What a belt drag would do to one tile of its path (REQ-BLD-BELT-DRAG).
 enum class BeltTileAction
 {

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 +138,67 @@ 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)
+{
+    if (b.type == BuildingType::ReprocessingPlant)
     {
-        if (recipeInputsAvailable(b, *recipe))
+        // One roll yields one of these, so each is measured on its own -- but all of them
+        // have to fit, since which one it will be is not known yet.
+        for (const RecipeOutput& out : recipe.outputs)
         {
-            return true;
+            if (!outputBufferHasRoom(b, ItemType{out.item}, out.amount))
+            {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    // A deterministic cycle deposits all of its outputs together. An item listed more
+    // than once is produced in the sum of those amounts, so it is judged once, as a sum.
+    std::map<ItemType, int> perCycle;
+    for (const RecipeOutput& out : recipe.outputs)
+    {
+        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 +217,10 @@ 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 +230,18 @@ 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 +44,39 @@ 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 output a cycle of this recipe could produce would fit -- the gate a
+// cycle has to pass before it may start (REQ-MAT-CYCLE). For a deterministic recipe that
+// is its own outputs. A Reprocessing Plant rolls one of its outputs per cycle
+// (REQ-BLD-REPROCESSING), so each possibility is judged on its own and all must fit: the
+// roll is committed the moment the cycle starts, and testing every outcome rather than
+// the rolled 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/ShipLayout.h

@@ -15,8 +15,23 @@ struct PlacedModule
     Rotation rotation;
 };
 
+inline bool operator==(const PlacedModule& a, const PlacedModule& b)
+{
+    return a.moduleId == b.moduleId && a.position == b.position && a.rotation == b.rotation;
+}
+
 // The complete module configuration for a shipyard's current ship (REQ-MOD-CONFIG).
 struct ShipLayoutConfig
 {
     std::vector<PlacedModule> placedModules;
 };
+
+// Deliberately order-sensitive: two layouts holding the same modules in a different
+// vector order compare unequal. This only decides whether applying a layout is a no-op
+// (REQ-MAT-INPUT-BUFFER), so the conservative answer is the safe one -- reporting a
+// change that is not one costs a buffer reset, reporting no change when there is one
+// would leave the shipyard stale.
+inline bool operator==(const ShipLayoutConfig& a, const ShipLayoutConfig& b)
+{
+    return a.placedModules == b.placedModules;
+}

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/BlueprintTest.cpp

@@ -56,7 +56,7 @@ static Rotation rotCCW(Rotation r)
     return Rotation::East;
 }
 
-// Mirror of BlueprintPanel::createBlueprintFromSelection: given per-building
+// Mirror of BlueprintLibrary::createBlueprintFromSelection: given per-building
 // (anchor, bodyCells, type, rotation), compute Blueprint with floor-division
 // bounding-box center and per-building tile offsets.
 struct BuildingSpec
@@ -149,7 +149,7 @@ static void applyRotationCCW(Blueprint& bp, const GameConfig& cfg)
     }
 }
 
-// Mirrors BlueprintPanel::createBlueprintFromSelection's player-placeable filter:
+// Mirrors BlueprintLibrary::createBlueprintFromSelection's player-placeable filter:
 // building types absent from buildings.toml (HQ, stations) or with playerPlaceable=false
 // are silently excluded before the bounding-box center and offsets are computed.
 static Blueprint buildBlueprintFiltered(const std::vector<BuildingSpec>& specs,

src/test/BuildModeControllerTest.cpp

@@ -82,7 +82,7 @@ TEST_CASE("Only one mode is active at a time", "[buildmode]")
 TEST_CASE("Entering builder mode announces that blueprint mode ended", "[buildmode]")
 {
     // Regression: entering builder mode used to drop the blueprint silently, so the
-    // blueprint panel kept its button highlighted for a mode that was over.
+    // blueprint library kept tracking an active blueprint for a mode that was over.
     BuildModeController controller;
     controller.enterBlueprintMode(makeBlueprint());
 

src/test/BuildingConfigTest.cpp

@@ -16,10 +16,10 @@
 #include "SimulationTestAccess.h"
 #include "TestConfig.h"
 
-// readBuildingConfig underpins the copy-settings gesture (REQ-BLD-COPY-CONFIG):
-// it extracts a building's recipe / schematic / layout / splitter filters so they
-// can be stamped onto a same-type building. It reads operational buildings and
-// construction sites alike.
+// readBuildingConfig underpins blueprint capture (REQ-UI-BLUEPRINT-STORAGE): it
+// extracts a building's recipe / schematic / layout / splitter filters so they can be
+// stored in the blueprint and reapplied on placement. It reads operational buildings
+// and construction sites alike.
 
 namespace
 {
@@ -60,7 +60,7 @@ const ShipDef* findAvailableSchematic(const GameConfig& cfg)
 }
 }  // namespace
 
-TEST_CASE("readBuildingConfig returns a miner's selected recipe", "[copyconfig]")
+TEST_CASE("readBuildingConfig returns a miner's selected recipe", "[blueprint]")
 {
     const GameConfig cfg = loadTestConfig();
     Simulation sim(loadTestConfig(), 7);
@@ -78,7 +78,7 @@ TEST_CASE("readBuildingConfig returns a miner's selected recipe", "[copyconfig]"
 }
 
 TEST_CASE("readBuildingConfig leaves recipe unset when nothing is selected",
-          "[copyconfig]")
+          "[blueprint]")
 {
     const GameConfig cfg = loadTestConfig();
     Simulation sim(loadTestConfig(), 7);
@@ -93,7 +93,7 @@ TEST_CASE("readBuildingConfig leaves recipe unset when nothing is selected",
 }
 
 TEST_CASE("readBuildingConfig returns a shipyard's schematic and layout",
-          "[copyconfig]")
+          "[blueprint]")
 {
     const GameConfig cfg = loadTestConfig();
     Simulation sim(loadTestConfig(), 7);
@@ -103,17 +103,28 @@ TEST_CASE("readBuildingConfig returns a shipyard's schematic and layout",
 
     const BuildingId id = placeOperational(sim, cfg, BuildingType::Shipyard, QPoint(0, 0));
     SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), id, schematic->id);
-    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), id, ShipLayoutConfig{});
+
+    // A real layout, not an empty one: applying an empty layout to a shipyard that has
+    // none is a no-op (REQ-MAT-INPUT-BUFFER), so it would leave nothing to read back.
+    ShipLayoutConfig layout;
+    PlacedModule placed;
+    placed.moduleId = "armor_plate";
+    placed.position = QPoint(0, 0);
+    placed.rotation = Rotation::East;
+    layout.placedModules.push_back(placed);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), id, layout);
 
     const std::optional<BuildingConfig> config = readBuildingConfig(sim, id);
     REQUIRE(config.has_value());
     CHECK(config->type == BuildingType::Shipyard);
     REQUIRE(config->recipeId.has_value());
     CHECK(*config->recipeId == schematic->id);
-    CHECK(config->shipLayout.has_value());
+    REQUIRE(config->shipLayout.has_value());
+    REQUIRE(config->shipLayout->placedModules.size() == 1);
+    CHECK(config->shipLayout->placedModules[0].moduleId == "armor_plate");
 }
 
-TEST_CASE("readBuildingConfig reads a queued construction site", "[copyconfig]")
+TEST_CASE("readBuildingConfig reads a queued construction site", "[blueprint]")
 {
     const GameConfig cfg = loadTestConfig();
     Simulation sim(loadTestConfig(), 7);
@@ -134,8 +145,105 @@ TEST_CASE("readBuildingConfig reads a queued construction site", "[copyconfig]")
     CHECK(*config->recipeId == "mine_iron_ore");
 }
 
-TEST_CASE("readBuildingConfig returns nullopt for an unknown id", "[copyconfig]")
+TEST_CASE("readBuildingConfig returns nullopt for an unknown id", "[blueprint]")
 {
     Simulation sim(loadTestConfig(), 7);
     CHECK_FALSE(readBuildingConfig(sim, kInvalidBuildingId).has_value());
 }
+
+// The derived facts a blueprint card shows (REQ-UI-BLUEPRINT-CARD). They live here
+// rather than in the dialog so they can be tested: src/ui is off the test include path.
+
+namespace
+{
+Blueprint makeBlueprint(const std::vector<BuildingType>& types)
+{
+    Blueprint blueprint;
+    for (const BuildingType type : types)
+    {
+        BlueprintBuilding building;
+        building.type     = type;
+        building.rotation = Rotation::East;
+        blueprint.buildings.push_back(building);
+    }
+    return blueprint;
+}
+}  // namespace
+
+TEST_CASE("computeBlueprintCost sums the constituent placement costs", "[blueprint]")
+{
+    const GameConfig cfg = loadTestConfig();
+
+    // belt 2 + belt 2 + miner 15.
+    const Blueprint blueprint = makeBlueprint(
+        {BuildingType::Belt, BuildingType::Belt, BuildingType::Miner});
+    CHECK(computeBlueprintCost(blueprint, cfg.buildings) == 19);
+}
+
+TEST_CASE("computeBlueprintCost ignores types absent from buildings.toml", "[blueprint]")
+{
+    const GameConfig cfg = loadTestConfig();
+    REQUIRE(cfg.buildings.findBuildingDef(BuildingType::Hq) == nullptr);
+
+    const Blueprint blueprint = makeBlueprint({BuildingType::Belt, BuildingType::Hq});
+    CHECK(computeBlueprintCost(blueprint, cfg.buildings) == 2);
+}
+
+TEST_CASE("computeBlueprintCost is zero for an empty blueprint", "[blueprint]")
+{
+    const GameConfig cfg = loadTestConfig();
+    CHECK(computeBlueprintCost(Blueprint{}, cfg.buildings) == 0);
+}
+
+TEST_CASE("summarizeBlueprintContents orders by descending count", "[blueprint]")
+{
+    const GameConfig cfg = loadTestConfig();
+
+    const Blueprint blueprint = makeBlueprint(
+        {BuildingType::Belt, BuildingType::Smelter, BuildingType::Miner,
+         BuildingType::Miner, BuildingType::Smelter, BuildingType::Miner});
+
+    const std::vector<BlueprintContentEntry> summary =
+        summarizeBlueprintContents(blueprint, cfg.buildings);
+    REQUIRE(summary.size() == 3);
+    CHECK(summary[0].buildingName == "Miner");
+    CHECK(summary[0].count == 3);
+    CHECK(summary[1].buildingName == "Smelter");
+    CHECK(summary[1].count == 2);
+    CHECK(summary[2].buildingName == "Belt");
+    CHECK(summary[2].count == 1);
+}
+
+TEST_CASE("summarizeBlueprintContents breaks ties in buildings.toml order", "[blueprint]")
+{
+    const GameConfig cfg = loadTestConfig();
+
+    // Miner is declared after Belt in buildings.toml, which is the order the build
+    // button bar lays its buttons out, so Belt wins the tie despite the equal counts
+    // and despite sorting later by enum value.
+    const Blueprint blueprint = makeBlueprint(
+        {BuildingType::Miner, BuildingType::Belt, BuildingType::Miner, BuildingType::Belt});
+
+    const std::vector<BlueprintContentEntry> summary =
+        summarizeBlueprintContents(blueprint, cfg.buildings);
+    REQUIRE(summary.size() == 2);
+    CHECK(summary[0].buildingName == "Belt");
+    CHECK(summary[1].buildingName == "Miner");
+}
+
+TEST_CASE("summarizeBlueprintContents spells multi-word ids as display names", "[blueprint]")
+{
+    const GameConfig cfg = loadTestConfig();
+
+    const Blueprint blueprint = makeBlueprint({BuildingType::TunnelEntry});
+    const std::vector<BlueprintContentEntry> summary =
+        summarizeBlueprintContents(blueprint, cfg.buildings);
+    REQUIRE(summary.size() == 1);
+    CHECK(summary[0].buildingName == "Tunnel Entry");
+}
+
+TEST_CASE("summarizeBlueprintContents is empty for an empty blueprint", "[blueprint]")
+{
+    const GameConfig cfg = loadTestConfig();
+    CHECK(summarizeBlueprintContents(Blueprint{}, cfg.buildings).empty());
+}

src/test/BuildingTest.cpp

@@ -14,6 +14,7 @@
 
 #include "BeltSystem.h"
 #include "Building.h"
+#include "BuildingBuffers.h"
 #include "BuildingSystem.h"
 #include "ConstructionSystem.h"
 #include "DeconstructionSystem.h"
@@ -495,13 +496,13 @@ 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 +513,49 @@ 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 +629,13 @@ 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 +646,13 @@ 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 +757,10 @@ 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 +770,7 @@ 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 +780,26 @@ 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 +886,8 @@ 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 +924,250 @@ 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("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 +1178,8 @@ 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;
@@ -1039,6 +1315,301 @@ TEST_CASE("BuildingSystem: findRotateInPlaceTarget works for a symmetric multi-t
     REQUIRE(*result == id);
 }
 
+// ---------------------------------------------------------------------------
+// resolveBlueprintGhost
+// ---------------------------------------------------------------------------
+
+// What a blueprint ghost does where it meets an existing building
+// (REQ-UI-BLUEPRINT-OVERLAP, REQ-UI-BLUEPRINT-TRANSFER). Blueprint placement never
+// rotates anything, so a coinciding building must either take the blueprint's settings
+// or already match it exactly.
+
+namespace
+{
+// A single-building blueprint, whose cursor sits on the ghost's own anchor unless a test
+// says otherwise. That gesture hit-tests the cursor for its transfer target.
+BlueprintGhostResolved resolveOne(const PlacementFixture& f, BuildingType type,
+                                  QPoint anchor, Rotation rotation)
+{
+    return resolveBlueprintGhost(f.state, f.cfg, type, anchor, rotation, anchor);
+}
+
+BlueprintGhostResolved resolveOneHovering(const PlacementFixture& f, BuildingType type,
+                                          QPoint anchor, Rotation rotation, QPoint cursorTile)
+{
+    return resolveBlueprintGhost(f.state, f.cfg, type, anchor, rotation, cursorTile);
+}
+
+// One ghost of a constellation: no cursor hit-test, judged purely on where it sits.
+BlueprintGhostResolved resolveInConstellation(const PlacementFixture& f, BuildingType type,
+                                              QPoint anchor, Rotation rotation)
+{
+    return resolveBlueprintGhost(f.state, f.cfg, type, anchor, rotation, std::nullopt);
+}
+}  // namespace
+
+TEST_CASE("isConfigurableBuildingType: only types with player-facing settings",
+          "[blueprint]")
+{
+    // The gate on whether a single-building blueprint transfers anything at all.
+    CHECK(isConfigurableBuildingType(BuildingType::Miner));
+    CHECK(isConfigurableBuildingType(BuildingType::Assembler));
+    CHECK(isConfigurableBuildingType(BuildingType::Shipyard));
+    CHECK(isConfigurableBuildingType(BuildingType::Splitter));
+
+    // 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));
+    CHECK_FALSE(isConfigurableBuildingType(BuildingType::TunnelExit));
+    CHECK_FALSE(isConfigurableBuildingType(BuildingType::Hq));
+}
+
+TEST_CASE("resolveBlueprintGhost: free valid cells place a new building", "[blueprint]")
+{
+    PlacementFixture f;
+
+    // Anchored on the asteroid (x < 0): a miner is all-asteroid cells. BuildingSystem's
+    // place() skips the terrain rules, but resolveBlueprintGhost applies them.
+    const BlueprintGhostResolved resolved =
+        resolveOne(f, BuildingType::Miner, QPoint(-2, 0), Rotation::East);
+    CHECK(resolved.action == BlueprintGhostAction::PlaceNew);
+    CHECK_FALSE(resolved.targetId.has_value());
+}
+
+TEST_CASE("resolveBlueprintGhost: terrain-invalid positions are invalid", "[blueprint]")
+{
+    PlacementFixture f;
+
+    // A miner is all-asteroid (A) cells, so it cannot sit out in space (x >= 0).
+    CHECK(resolveOne(f, BuildingType::Miner, QPoint(5, 0), Rotation::East).action
+          == BlueprintGhostAction::Invalid);
+}
+
+TEST_CASE("resolveBlueprintGhost: overlapping a different building type is invalid",
+          "[blueprint]")
+{
+    PlacementFixture f;
+
+    f.bs.place(f.state, BuildingType::Belt, QPoint(-1, 0), Rotation::East, 0);
+
+    CHECK(resolveOne(f, BuildingType::Splitter, QPoint(-1, 0), Rotation::East).action
+          == BlueprintGhostAction::Invalid);
+}
+
+TEST_CASE("resolveBlueprintGhost: a partial overlap of the same type is invalid",
+          "[blueprint]")
+{
+    PlacementFixture f;
+
+    // Smelter at (-3,0) covers (-3,0),(-2,0),(-3,1),(-2,1); a ghost at (-2,0) covers only
+    // two of those, so it coincides with nothing and is an ordinary occupied overlap.
+    // 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);
+
+    // 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",
+          "[blueprint]")
+{
+    PlacementFixture f;
+
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::Miner, QPoint(-2, 0), Rotation::East, 0).value();
+
+    const BlueprintGhostResolved resolved =
+        resolveOne(f, BuildingType::Miner, QPoint(-2, 0), Rotation::East);
+    REQUIRE(resolved.action == BlueprintGhostAction::Transfer);
+    REQUIRE(resolved.targetId.has_value());
+    CHECK(*resolved.targetId == id);
+}
+
+TEST_CASE("resolveBlueprintGhost: a transfer ignores the target's rotation", "[blueprint]")
+{
+    // A transfer never rotates anything, so which way the target faces cannot matter
+    // (REQ-UI-BLUEPRINT-TRANSFER). The ghost snaps to the target's facing rather than
+    // keeping the blueprint's.
+    PlacementFixture f;
+
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::Splitter, QPoint(-1, 0), Rotation::East, 0).value();
+
+    const BlueprintGhostResolved resolved =
+        resolveOne(f, BuildingType::Splitter, QPoint(-1, 0), Rotation::North);
+    REQUIRE(resolved.action == BlueprintGhostAction::Transfer);
+    REQUIRE(resolved.targetId.has_value());
+    CHECK(*resolved.targetId == id);
+    CHECK(resolved.ghostRotation == Rotation::East);
+}
+
+TEST_CASE("resolveBlueprintGhost: a single-building blueprint transfers from anywhere on the target",
+          "[blueprint]")
+{
+    // The point of hit-testing the cursor instead of comparing footprints. Coincidence
+    // needs the ghost's anchor to land on the target's own anchor, so with a 2x2 body
+    // three of its four tiles missed and read as an ordinary overlap. Hovering any body
+    // tile now targets it, and the ghost snaps onto the building
+    // (REQ-UI-BLUEPRINT-TRANSFER).
+    PlacementFixture f;
+
+    // Assembler body covers (-3,0),(-2,0),(-3,1),(-2,1); its anchor is (-3,0).
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::Assembler, QPoint(-3, 0), Rotation::East, 0).value();
+
+    const QPoint offAnchorTile(-2, 1);
+    const BlueprintGhostResolved resolved =
+        resolveOneHovering(f, BuildingType::Assembler, offAnchorTile, Rotation::East,
+                           offAnchorTile);
+    REQUIRE(resolved.action == BlueprintGhostAction::Transfer);
+    CHECK(*resolved.targetId == id);
+    CHECK(resolved.ghostAnchor == QPoint(-3, 0));
+
+    // The same misaligned ghost inside a constellation still just overlaps invalidly:
+    // a layout is placed where the blueprint puts it, and nothing snaps.
+    CHECK(resolveInConstellation(f, BuildingType::Assembler, offAnchorTile, Rotation::East).action
+          == BlueprintGhostAction::Invalid);
+}
+
+TEST_CASE("resolveBlueprintGhost: hovering a different building type does not transfer",
+          "[blueprint]")
+{
+    PlacementFixture f;
+
+    f.bs.place(f.state, BuildingType::Smelter, QPoint(-3, 0), Rotation::East, 0);
+
+    // A miner blueprint over a smelter: the cursor hit-test only matches its own type.
+    CHECK(resolveOne(f, BuildingType::Miner, QPoint(-3, 0), Rotation::East).action
+          == BlueprintGhostAction::Invalid);
+}
+
+TEST_CASE("resolveBlueprintGhost: a construction site is a transfer target too",
+          "[blueprint]")
+{
+    PlacementFixture f;
+
+    // Not ticked to completion, so it is still queued (REQ-BLD-SITE-CONFIG).
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::Assembler, QPoint(-3, 0), Rotation::East, 0).value();
+    REQUIRE_FALSE(getAllSites(f.state).empty());
+
+    const BlueprintGhostResolved resolved =
+        resolveOne(f, BuildingType::Assembler, QPoint(-3, 0), Rotation::East);
+    REQUIRE(resolved.action == BlueprintGhostAction::Transfer);
+    CHECK(*resolved.targetId == id);
+}
+
+TEST_CASE("resolveBlueprintGhost: a single building with no settings overlaps instead",
+          "[blueprint]")
+{
+    // A belt carries nothing to transfer, so the same footprint is a compatible overlap
+    // when the facings match -- and invalid when they do not, since nothing here may
+    // re-orient it (REQ-UI-BLUEPRINT-OVERLAP).
+    PlacementFixture f;
+
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::Belt, QPoint(-1, 0), Rotation::East, 0).value();
+
+    const BlueprintGhostResolved matching =
+        resolveOne(f, BuildingType::Belt, QPoint(-1, 0), Rotation::East);
+    REQUIRE(matching.action == BlueprintGhostAction::CompatibleOverlap);
+    CHECK(*matching.targetId == id);
+
+    CHECK(resolveOne(f, BuildingType::Belt, QPoint(-1, 0), Rotation::North).action
+          == BlueprintGhostAction::Invalid);
+}
+
+TEST_CASE("resolveBlueprintGhost: a constellation transfers onto a matching building",
+          "[blueprint]")
+{
+    // Blueprint size does not gate the transfer itself: a configurable building already
+    // standing where the blueprint wants it, facing the same way, takes its settings
+    // whatever else the blueprint holds (REQ-UI-BLUEPRINT-TRANSFER).
+    PlacementFixture f;
+
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::Miner, QPoint(-2, 0), Rotation::East, 0).value();
+
+    const BlueprintGhostResolved resolved =
+        resolveInConstellation(f, BuildingType::Miner, QPoint(-2, 0), Rotation::East);
+    REQUIRE(resolved.action == BlueprintGhostAction::Transfer);
+    CHECK(*resolved.targetId == id);
+}
+
+TEST_CASE("resolveBlueprintGhost: a constellation still requires a matching rotation",
+          "[blueprint]")
+{
+    // Only the single-building gesture is forgiving about facing. A constellation's
+    // ghosts stay where the blueprint puts them, and one that cannot be re-oriented to
+    // match blocks the whole placement (REQ-UI-BLUEPRINT-OVERLAP).
+    PlacementFixture f;
+
+    f.bs.place(f.state, BuildingType::Splitter, QPoint(-1, 0), Rotation::East, 0);
+
+    CHECK(resolveInConstellation(f, BuildingType::Splitter, QPoint(-1, 0), Rotation::North).action
+          == BlueprintGhostAction::Invalid);
+}
+
+TEST_CASE("resolveBlueprintGhost: a constellation mixes transfers and plain overlaps",
+          "[blueprint]")
+{
+    // One drop can reconfigure some of the buildings already there while leaving others
+    // alone: the split is by whether the type has settings at all, not by blueprint size
+    // (REQ-UI-BLUEPRINT-OVERLAP).
+    PlacementFixture f;
+
+    const BuildingId minerId =
+        f.bs.place(f.state, BuildingType::Miner, QPoint(-2, 0), Rotation::East, 0).value();
+    const BuildingId smelterId =
+        f.bs.place(f.state, BuildingType::Smelter, QPoint(-5, 0), Rotation::East, 0).value();
+
+    const BlueprintGhostResolved miner =
+        resolveInConstellation(f, BuildingType::Miner, QPoint(-2, 0), Rotation::East);
+    REQUIRE(miner.action == BlueprintGhostAction::Transfer);
+    CHECK(*miner.targetId == minerId);
+
+    // 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::Transfer);
+    CHECK(*smelter.targetId == smelterId);
+}
+
+TEST_CASE("resolveBlueprintGhost: an identical tunnel is a compatible overlap", "[blueprint]")
+{
+    // findRotateInPlaceTarget refuses tunnels because re-orienting one is unsupported.
+    // Nothing is re-oriented here, so that reason does not apply and the tunnel the
+    // blueprint wants -- already there, same facing -- is simply left alone.
+    PlacementFixture f;
+
+    const BuildingId id =
+        f.bs.place(f.state, BuildingType::TunnelEntry, QPoint(-1, 0), Rotation::East, 0).value();
+    f.bs.place(f.state, BuildingType::TunnelExit, QPoint(-2, 0), Rotation::East, 0);
+
+    REQUIRE_FALSE(
+        findRotateInPlaceTarget(f.state, f.cfg, BuildingType::TunnelEntry, QPoint(-1, 0), Rotation::East)
+            .has_value());
+
+    const BlueprintGhostResolved resolved =
+        resolveInConstellation(f, BuildingType::TunnelEntry, QPoint(-1, 0), Rotation::East);
+    REQUIRE(resolved.action == BlueprintGhostAction::CompatibleOverlap);
+    CHECK(*resolved.targetId == id);
+}
+
 // ---------------------------------------------------------------------------
 // rotateInPlace
 // ---------------------------------------------------------------------------
@@ -1229,41 +1800,187 @@ 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->outputs.front().item;
+        int cycleOutput = 0;
+        for (const RecipeOutput& out : assemblerRecipe->outputs)
+        {
+            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.outputs) { total += out.amount; }
+            if (total >= 2) { multiOutputRecipe = &r; break; }
+        }
+        REQUIRE(multiOutputRecipe != nullptr);
+
+        int cycleOutput = 0;
+        for (const RecipeOutput& out : multiOutputRecipe->outputs)
+        {
+            cycleOutput += out.amount;
+        }
+        const std::string outputItemId = multiOutputRecipe->outputs.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->outputs.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->outputs.front().item;
+        const std::string lastItemId  = reprocessingRecipe->outputs.back().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")
@@ -1281,7 +1998,7 @@ 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

@@ -390,39 +390,6 @@ 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 +1,328 @@
+#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);
+}
+
+TEST_CASE("ControlAction: Q enters deconstruct mode, or leaves the active one",
+          "[controls]")
+{
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, generalContext())
+            == ControlAction::EnterDeconstruct);
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, selectionContext())
+            == ControlAction::EnterDeconstruct);
+    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);
+}
+
+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(contains(selection, ControlAction::AddToSelection));
+    REQUIRE(contains(selection, ControlAction::AddAreaToSelection));
+    REQUIRE(contains(selection, ControlAction::CreateBlueprint));
+    REQUIRE(contains(selection, ControlAction::EnterDeconstruct));
+}

src/test/FloatingPanelPlacementTest.cpp

@@ -0,0 +1,231 @@
+#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);
+}
+
+static const int kMarginPx = 8;
+
+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, kMarginPx)
+            == PanelSide::Right);
+}
+
+TEST_CASE("The panel goes left when the right cannot hold it", "[layout]")
+{
+    // A selection near the right edge leaves 100 px there, not enough for a 300 px
+    // panel, and the left is wide open.
+    REQUIRE(chooseSide(makeBand(), QRect(880, 100, 20, 60), 300, kMarginPx)
+            == PanelSide::Left);
+}
+
+TEST_CASE("Fitting on neither side, the panel takes the roomier one", "[layout]")
+{
+    // A bounding box spanning most of the view: 192 px free on the left, 92 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, kMarginPx)
+            == PanelSide::Left);
+    REQUIRE(chooseSide(makeBand(), QRect(100, 100, 700, 200), 300, kMarginPx)
+            == 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 margin, growing away from the selection,
+    // top edge on the anchor's top edge.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 120, 60, 60),
+                                           PanelSide::Right, QSize(300, 200), {},
+                                           kMarginPx);
+    REQUIRE(placed == QRect(168, 120, 300, 200));
+
+    const QRect placedLeft = placeBesideAnchor(makeBand(), QRect(500, 120, 60, 60),
+                                               PanelSide::Left, QSize(300, 200), {},
+                                               kMarginPx);
+    REQUIRE(placedLeft == QRect(192, 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), {},
+                                           kMarginPx);
+    REQUIRE(placed == QRect(168, 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 margin (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,
+                                           kMarginPx);
+    REQUIRE(placed == QRect(192, 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), {},
+                                           kMarginPx);
+    REQUIRE(placed == QRect(168, 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), {},
+                                           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

@@ -262,6 +262,123 @@ TEST_CASE("Shipyard: setShipLayout cancels in-progress production",
     CHECK_FALSE(b2->production.has_value());
 }
 
+// Applying a configuration a building already has is a no-op (REQ-MAT-INPUT-BUFFER).
+// setRecipe has always worked this way; setShipLayout did not, and wiped the shipyard
+// on every re-apply. That matters now that a blueprint configuration transfer
+// (REQ-UI-BLUEPRINT-TRANSFER) can be clicked repeatedly onto matching shipyards.
+
+TEST_CASE("Shipyard: re-applying the same layout keeps production and buffers",
+          "[modules][shipyard]")
+{
+    Simulation sim(loadTestConfig(), 42);
+    const ShipDef* def = findSchematic(sim.getConfig(), "interceptor");
+    REQUIRE(def != nullptr);
+    const BuildingDef* yardDef = findShipyardDef(sim.getConfig());
+    REQUIRE(yardDef != nullptr);
+
+    const BuildingId yardId = placeShipyard(sim, *yardDef);
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId, "interceptor");
+
+    ShipLayoutConfig layout;
+    PlacedModule pm;
+    pm.moduleId = "armor_plate";
+    pm.position = QPoint(0, 0);
+    pm.rotation = Rotation::East;
+    layout.placedModules.push_back(pm);
+
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, layout);
+    fillMaterials(sim, yardId, *def, layout);
+    sim.tick();
+
+    const Building* before = findBuilding(sim.getFactoryState(), yardId);
+    REQUIRE(before != nullptr);
+    REQUIRE(before->production.has_value());
+    const Tick completesAt = before->production->completesAt;
+
+    // A separately built but equal layout: equality is by value, not by identity.
+    ShipLayoutConfig sameLayout;
+    sameLayout.placedModules.push_back(pm);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, sameLayout);
+
+    const Building* after = findBuilding(sim.getFactoryState(), yardId);
+    REQUIRE(after != nullptr);
+    REQUIRE(after->production.has_value());
+    CHECK(after->production->completesAt == completesAt);
+    CHECK(after->inputBuffer.caps.at(ItemType{"iron_ingot"}) == 10);
+}
+
+TEST_CASE("Shipyard: an empty layout on an unconfigured shipyard changes nothing",
+          "[modules][shipyard]")
+{
+    // An unset layout and an empty one are the same state everywhere that matters, so
+    // clearing an already-unconfigured shipyard must not cancel its cycle. This is the
+    // case a transfer from a layout-less source shipyard produces.
+    Simulation sim(loadTestConfig(), 42);
+    const ShipDef* def = findSchematic(sim.getConfig(), "interceptor");
+    REQUIRE(def != nullptr);
+    const BuildingDef* yardDef = findShipyardDef(sim.getConfig());
+    REQUIRE(yardDef != nullptr);
+
+    const BuildingId yardId = placeShipyard(sim, *yardDef);
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId, "interceptor");
+
+    ShipLayoutConfig emptyLayout;
+    fillMaterials(sim, yardId, *def, emptyLayout);
+    sim.tick();
+
+    const Building* before = findBuilding(sim.getFactoryState(), yardId);
+    REQUIRE(before != nullptr);
+    REQUIRE(before->production.has_value());
+    REQUIRE_FALSE(before->shipLayout.has_value());
+
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, emptyLayout);
+
+    const Building* after = findBuilding(sim.getFactoryState(), yardId);
+    REQUIRE(after != nullptr);
+    CHECK(after->production.has_value());
+    CHECK_FALSE(after->shipLayout.has_value());
+}
+
+TEST_CASE("Shipyard: the same modules in a different order count as a change",
+          "[modules][shipyard]")
+{
+    // Layout equality is deliberately order-sensitive (see ShipLayout.h): the safe
+    // answer when in doubt is "changed", which costs a buffer reset rather than
+    // leaving a shipyard building the wrong ship.
+    Simulation sim(loadTestConfig(), 42);
+    const ShipDef* def = findSchematic(sim.getConfig(), "interceptor");
+    REQUIRE(def != nullptr);
+    const BuildingDef* yardDef = findShipyardDef(sim.getConfig());
+    REQUIRE(yardDef != nullptr);
+
+    const BuildingId yardId = placeShipyard(sim, *yardDef);
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId, "interceptor");
+
+    PlacedModule armor;
+    armor.moduleId = "armor_plate";
+    armor.position = QPoint(0, 0);
+    armor.rotation = Rotation::East;
+    PlacedModule sensor;
+    sensor.moduleId = "sensor_booster";
+    sensor.position = QPoint(1, 0);
+    sensor.rotation = Rotation::East;
+
+    ShipLayoutConfig layout;
+    layout.placedModules.push_back(armor);
+    layout.placedModules.push_back(sensor);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, layout);
+    fillMaterials(sim, yardId, *def, layout);
+    sim.tick();
+    REQUIRE(findBuilding(sim.getFactoryState(), yardId)->production.has_value());
+
+    ShipLayoutConfig reordered;
+    reordered.placedModules.push_back(sensor);
+    reordered.placedModules.push_back(armor);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, reordered);
+
+    CHECK_FALSE(findBuilding(sim.getFactoryState(), yardId)->production.has_value());
+}
+
 TEST_CASE("Shipyard: builds a bare hull when no layout is configured",
           "[modules][shipyard]")
 {

src/ui/BlueprintLibrary.cpp

@@ -0,0 +1,206 @@
+#include "BlueprintLibrary.h"
+
+#include <cstddef>
+#include <utility>
+
+#include <QCoreApplication>
+#include <QFile>
+#include <QMessageBox>
+#include <QObject>
+#include <QStringList>
+
+#include "BlueprintPlacementRequestedEvent.h"
+#include "BlueprintSerializer.h"
+#include "EventManager.h"
+#include "ExitBlueprintModeRequestedEvent.h"
+
+#include "BuildingConfig.h"
+#include "Simulation.h"
+
+BlueprintLibrary::BlueprintLibrary(Simulation* sim, const GameConfig* config,
+                                   QWidget* dialogParent)
+    : m_sim(sim)
+    , m_config(config)
+    , m_dialogParent(dialogParent)
+{
+    loadFromDisk();
+    registerForEvents();
+}
+
+BlueprintLibrary::~BlueprintLibrary()
+{
+    saveToDisk();
+    unregisterForEvents();
+}
+
+bool BlueprintLibrary::getCanCaptureSelection() const
+{
+    // A construction site counts the same as an operational building (REQ-UI-BLUEPRINT-CREATE).
+    return selectionHasPlaceableBuilding(*m_sim, m_selectedBuildingIds);
+}
+
+bool BlueprintLibrary::getHasTemporaryBlueprint() const
+{
+    return m_temporaryBlueprint.has_value();
+}
+
+void BlueprintLibrary::saveSelectionAs(const QString& name)
+{
+    Blueprint blueprint = createBlueprintFromSelection();
+    if (blueprint.buildings.empty()) { return; }
+
+    blueprint.name = name;
+    m_blueprints.push_back(std::move(blueprint));
+}
+
+const std::vector<Blueprint>& BlueprintLibrary::getBlueprints() const
+{
+    return m_blueprints;
+}
+
+QString BlueprintLibrary::getContentsSummary(int index) const
+{
+    if (index < 0 || index >= static_cast<int>(m_blueprints.size())) { return QString(); }
+
+    QStringList entries;
+    for (const BlueprintContentEntry& entry : summarizeBlueprintContents(
+             m_blueprints[static_cast<std::size_t>(index)], m_config->buildings))
+    {
+        // The same "<type> x <count>" notation the building multi-selection summary
+        // uses (REQ-UI-MULTI-SELECTION), which also sidesteps plural forms.
+        entries << QObject::tr("%1 x %2")
+            .arg(QString::fromStdString(entry.buildingName))
+            .arg(entry.count);
+    }
+    return entries.join(QStringLiteral(", "));
+}
+
+int BlueprintLibrary::getCost(int index) const
+{
+    if (index < 0 || index >= static_cast<int>(m_blueprints.size())) { return 0; }
+    return computeBlueprintCost(m_blueprints[static_cast<std::size_t>(index)],
+                                m_config->buildings);
+}
+
+bool BlueprintLibrary::getCanAfford(int index) const
+{
+    return m_sim->getBuildingBlocksStock() >= getCost(index);
+}
+
+void BlueprintLibrary::remove(int index)
+{
+    if (index < 0 || index >= static_cast<int>(m_blueprints.size())) { return; }
+
+    if (m_activeIndex == index)
+    {
+        m_activeIndex = std::nullopt;
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<ExitBlueprintModeRequestedEvent>());
+    }
+    else if (m_activeIndex.has_value() && *m_activeIndex > index)
+    {
+        --*m_activeIndex;
+    }
+    m_blueprints.erase(m_blueprints.begin() + index);
+}
+
+void BlueprintLibrary::beginPlacement(int index)
+{
+    if (index < 0 || index >= static_cast<int>(m_blueprints.size())) { return; }
+
+    m_activeIndex = index;
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<BlueprintPlacementRequestedEvent>(
+            m_blueprints[static_cast<std::size_t>(index)]));
+}
+
+void BlueprintLibrary::handleEvent(std::shared_ptr<const SelectionChangedEvent> event)
+{
+    m_selectedBuildingIds = event->ids;
+}
+
+void BlueprintLibrary::handleEvent(std::shared_ptr<const BlueprintModeExitedEvent> /*event*/)
+{
+    // Only the saved-blueprint index is cleared. A temporary blueprint deliberately
+    // survives its placement mode so V can re-enter it (REQ-UI-BLUEPRINT-TEMP).
+    m_activeIndex = std::nullopt;
+}
+
+void BlueprintLibrary::handleEvent(
+    std::shared_ptr<const TemporaryBlueprintCaptureRequestedEvent> /*event*/)
+{
+    // C (REQ-UI-BLUEPRINT-TEMP): capture the current selection and enter placement mode
+    // for it, without naming it, listing it, or persisting it. If nothing player-placeable
+    // is selected, do nothing at all -- in particular, keep the previous temporary
+    // blueprint, which V can still place.
+    Blueprint blueprint = createBlueprintFromSelection();
+    if (blueprint.buildings.empty()) { return; }
+
+    m_temporaryBlueprint = std::move(blueprint);
+    // No saved blueprint is active while a temporary one is being placed.
+    m_activeIndex = std::nullopt;
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<BlueprintPlacementRequestedEvent>(*m_temporaryBlueprint));
+}
+
+void BlueprintLibrary::handleEvent(
+    std::shared_ptr<const TemporaryBlueprintPlaceRequestedEvent> /*event*/)
+{
+    // V (REQ-UI-BLUEPRINT-TEMP): re-enter placement mode for the temporary blueprint,
+    // capturing nothing. With none captured, nothing happens -- no mode is entered and
+    // whichever mode is active is left alone. Affordability is not checked here, matching
+    // C; cost is enforced at placement (REQ-UI-BLUEPRINT-PLACE). The blueprint is copied,
+    // not moved: it stays available for the next V.
+    if (!m_temporaryBlueprint.has_value()) { return; }
+
+    m_activeIndex = std::nullopt;
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<BlueprintPlacementRequestedEvent>(*m_temporaryBlueprint));
+}
+
+void BlueprintLibrary::handleEvent(std::shared_ptr<const GameResetEvent> /*event*/)
+{
+    // A restart begins a new run, and the temporary blueprint belongs to the old one
+    // (REQ-UI-BLUEPRINT-TEMP). The saved blueprints are not run state and stay.
+    m_temporaryBlueprint = std::nullopt;
+}
+
+Blueprint BlueprintLibrary::createBlueprintFromSelection() const
+{
+    // Capture is shared, testable logic in lib/sim: it resolves each selected id as an
+    // operational building or a construction site alike (REQ-UI-BLUEPRINT-CREATE,
+    // REQ-UI-BLUEPRINT-STORAGE).
+    return captureBlueprintFromSelection(*m_sim, m_selectedBuildingIds);
+}
+
+void BlueprintLibrary::loadFromDisk()
+{
+    // Load at startup (REQ-UI-BLUEPRINT-LOAD). Missing file: start empty, no error.
+    const QString path = QCoreApplication::applicationDirPath() + "/blueprints.toml";
+    QFile file(path);
+    if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) { return; }
+    try
+    {
+        m_blueprints = BlueprintSerializer::deserialize(file.readAll().toStdString());
+    }
+    catch (const std::exception& e)
+    {
+        QMessageBox::critical(m_dialogParent, QObject::tr("Load Failed"),
+            QObject::tr("Failed to load blueprints:\n%1").arg(e.what()));
+        m_blueprints.clear();
+    }
+}
+
+void BlueprintLibrary::saveToDisk() const
+{
+    // Persist on shutdown; write errors are silently ignored (REQ-UI-BLUEPRINT-SAVE).
+    const QString path = QCoreApplication::applicationDirPath() + "/blueprints.toml";
+    QFile file(path);
+    if (!file.open(QIODevice::WriteOnly | QIODevice::Text)) { return; }
+    try
+    {
+        const std::string content = BlueprintSerializer::serialize(m_blueprints);
+        file.write(QByteArray::fromStdString(content));
+    }
+    catch (...) {}
+}

src/ui/BlueprintLibrary.h

@@ -0,0 +1,106 @@
+#pragma once
+
+#include <optional>
+#include <vector>
+
+#include <QString>
+
+#include "Blueprint.h"
+#include "BlueprintModeExitedEvent.h"
+#include "BuildingId.h"
+#include "EventHandler.h"
+#include "GameConfig.h"
+#include "GameResetEvent.h"
+#include "SelectionChangedEvent.h"
+#include "TemporaryBlueprintCaptureRequestedEvent.h"
+#include "TemporaryBlueprintPlaceRequestedEvent.h"
+
+class Simulation;
+class QWidget;
+
+// The player's saved blueprints: the list itself, its persistence (REQ-UI-BLUEPRINT-SAVE,
+// REQ-UI-BLUEPRINT-LOAD), capture from the current selection (REQ-UI-BLUEPRINT-CREATE,
+// REQ-UI-BLUEPRINT-TEMP), and entry into blueprint placement mode.
+//
+// Deliberately not a widget: blueprints have no permanent place on screen any more
+// (REQ-UI-BLUEPRINT-DIALOG), and the modal dialogs that present them must be driven from
+// MainWindow, the only widget that can pause the game (ModalPauseScope) and raise the dim
+// overlay. This class is the model those dialogs read and mutate.
+class BlueprintLibrary
+    : public CombinedEventHandler<SelectionChangedEvent,
+                                  BlueprintModeExitedEvent,
+                                  TemporaryBlueprintCaptureRequestedEvent,
+                                  TemporaryBlueprintPlaceRequestedEvent,
+                                  GameResetEvent>
+{
+public:
+    // dialogParent parents the load-failure message box (REQ-UI-BLUEPRINT-LOAD) and is
+    // not owned.
+    BlueprintLibrary(Simulation* sim, const GameConfig* config, QWidget* dialogParent);
+    ~BlueprintLibrary();
+
+    // True when the current selection holds at least one player-placeable building or
+    // construction site -- the condition under which Ctrl+C has any effect
+    // (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);
+
+    const std::vector<Blueprint>& getBlueprints() const;
+
+    // The blueprint's contents line, ready for its card: one "<name> x <count>" entry
+    // per building type, comma-separated, ordered by summarizeBlueprintContents
+    // (REQ-UI-BLUEPRINT-CARD).
+    QString getContentsSummary(int index) const;
+
+    // Sum of the constituent buildings' placement costs (REQ-UI-BLUEPRINT-CARD).
+    int getCost(int index) const;
+
+    // Whether the player can currently afford the blueprint's total cost, which is what
+    // enables or greys out its card (REQ-UI-BLUEPRINT-CARD).
+    bool getCanAfford(int index) const;
+
+    // Removes the blueprint, exiting blueprint placement mode if it was the active one
+    // (REQ-UI-BLUEPRINT-DELETE).
+    void remove(int index);
+
+    // Enters blueprint placement mode for the blueprint (REQ-UI-BLUEPRINT-MODE).
+    void beginPlacement(int index);
+
+private:
+    void handleEvent(std::shared_ptr<const SelectionChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const BlueprintModeExitedEvent> event) override;
+    void handleEvent(
+        std::shared_ptr<const TemporaryBlueprintCaptureRequestedEvent> event) override;
+    void handleEvent(
+        std::shared_ptr<const TemporaryBlueprintPlaceRequestedEvent> event) override;
+    void handleEvent(std::shared_ptr<const GameResetEvent> event) override;
+
+    Blueprint createBlueprintFromSelection() const;
+    void      loadFromDisk();
+    void      saveToDisk() const;
+
+    // The simulation is the single source of truth for the block stock and the
+    // selection; the change events are only refresh signals.
+    Simulation*             m_sim;
+    const GameConfig*       m_config;
+    QWidget*                m_dialogParent;
+    std::vector<BuildingId> m_selectedBuildingIds;
+    std::vector<Blueprint>  m_blueprints;
+    // Index of the blueprint currently in placement mode, so deleting it can exit that
+    // mode (REQ-UI-BLUEPRINT-DELETE). nullopt = no saved blueprint is being placed.
+    std::optional<int>      m_activeIndex;
+    // The one unnamed blueprint captured with C and re-placed with V
+    // (REQ-UI-BLUEPRINT-TEMP). Deliberately kept out of m_blueprints: it is never named,
+    // never listed in the selection dialog, and never written to blueprints.toml. It
+    // outlives its placement mode, so V can re-enter it. nullopt = none captured since
+    // startup or the last restart.
+    std::optional<Blueprint> m_temporaryBlueprint;
+};

src/ui/BlueprintPanel.cpp

@@ -1,281 +0,0 @@
-#include "BlueprintPanel.h"
-
-#include <algorithm>
-#include <climits>
-
-#include <QCoreApplication>
-#include <QFile>
-#include <QHBoxLayout>
-#include <QInputDialog>
-#include <QMessageBox>
-#include <QPushButton>
-#include <QScrollArea>
-#include <QVBoxLayout>
-
-#include "BlueprintPlacementRequestedEvent.h"
-#include "BlueprintSerializer.h"
-#include "BuildingBlocksChangedEvent.h"
-#include "EventManager.h"
-#include "ExitBlueprintModeRequestedEvent.h"
-
-#include "Building.h"
-#include "BuildingConfig.h"
-#include "BuildingSystem.h"
-#include "Simulation.h"
-
-BlueprintPanel::BlueprintPanel(Simulation* sim, const GameConfig* config, QWidget* parent)
-    : QWidget(parent)
-    , m_sim(sim)
-    , m_config(config)
-{
-    QVBoxLayout* layout = new QVBoxLayout(this);
-    layout->setContentsMargins(4, 4, 4, 4);
-    layout->setSpacing(4);
-
-    m_createBtn = new QPushButton(tr("Create Blueprint"), this);
-    m_createBtn->setFixedHeight(48);
-    m_createBtn->setEnabled(false);
-    layout->addWidget(m_createBtn);
-
-    QScrollArea* scrollArea = new QScrollArea(this);
-    scrollArea->setWidgetResizable(true);
-    scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
-
-    m_buttonsContainer = new QWidget(scrollArea);
-    m_buttonsLayout    = new QVBoxLayout(m_buttonsContainer);
-    m_buttonsLayout->setContentsMargins(0, 0, 0, 0);
-    m_buttonsLayout->setSpacing(4);
-    m_buttonsLayout->addStretch();
-
-    scrollArea->setWidget(m_buttonsContainer);
-    layout->addWidget(scrollArea, 1);
-
-    connect(m_createBtn, &QPushButton::clicked, this, &BlueprintPanel::onCreateClicked);
-
-    loadFromDisk();
-    rebuildButtons();
-
-    registerForEvents();
-}
-
-BlueprintPanel::~BlueprintPanel()
-{
-    saveToDisk();
-    unregisterForEvents();
-}
-
-void BlueprintPanel::onSelectionChanged(const std::vector<BuildingId>& ids)
-{
-    m_selectedBuildingIds = ids;
-    refreshButtonStates();
-}
-
-void BlueprintPanel::handleEvent(std::shared_ptr<const BuildingBlocksChangedEvent> /*event*/)
-{
-    refreshButtonStates();
-}
-
-void BlueprintPanel::clearActiveBlueprintButton()
-{
-    if (m_activeIndex.has_value() && *m_activeIndex < static_cast<int>(m_blueprintButtons.size()))
-    {
-        m_blueprintButtons[static_cast<std::size_t>(*m_activeIndex)]->setChecked(false);
-    }
-    m_activeIndex = std::nullopt;
-    refreshButtonStates();
-}
-
-void BlueprintPanel::onCreateClicked()
-{
-    if (m_selectedBuildingIds.empty()) { return; }
-
-    Blueprint bp = createBlueprintFromSelection();
-    if (bp.buildings.empty()) { return; }
-
-    bool ok = false;
-    const QString name = QInputDialog::getText(
-        this, tr("Create Blueprint"), tr("Blueprint name:"), QLineEdit::Normal, QString(), &ok);
-    if (!ok || name.trimmed().isEmpty()) { return; }
-
-    bp.name = name.trimmed();
-    m_blueprints.push_back(bp);
-    rebuildButtons();
-}
-
-void BlueprintPanel::onDeleteBlueprintClicked(int index)
-{
-    if (m_activeIndex == index)
-    {
-        m_activeIndex = std::nullopt;
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<ExitBlueprintModeRequestedEvent>());
-    }
-    else if (m_activeIndex.has_value() && *m_activeIndex > index)
-    {
-        --*m_activeIndex;
-    }
-    m_blueprints.erase(m_blueprints.begin() + index);
-    rebuildButtons();
-}
-
-void BlueprintPanel::onBlueprintButtonClicked(int index)
-{
-    if (index < 0 || index >= static_cast<int>(m_blueprints.size())) { return; }
-
-    if (m_activeIndex == index)
-    {
-        clearActiveBlueprintButton();
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<ExitBlueprintModeRequestedEvent>());
-        return;
-    }
-
-    if (m_activeIndex.has_value() && *m_activeIndex < static_cast<int>(m_blueprintButtons.size()))
-    {
-        m_blueprintButtons[static_cast<std::size_t>(*m_activeIndex)]->setChecked(false);
-    }
-
-    m_activeIndex = index;
-    m_blueprintButtons[static_cast<std::size_t>(index)]->setChecked(true);
-    EventManager::getInstance()->sendEventImmediately(
-        std::make_shared<BlueprintPlacementRequestedEvent>(m_blueprints[static_cast<std::size_t>(index)]));
-}
-
-Blueprint BlueprintPanel::createBlueprintFromSelection() const
-{
-    // Capture is shared, testable logic in lib/sim: it resolves each selected id as an
-    // operational building or a construction site alike (REQ-UI-BLUEPRINT-CREATE,
-    // REQ-UI-BLUEPRINT-STORAGE).
-    return captureBlueprintFromSelection(*m_sim, m_selectedBuildingIds);
-}
-
-int BlueprintPanel::computeBlueprintCost(const Blueprint& bp) const
-{
-    int total = 0;
-    for (const BlueprintBuilding& bb : bp.buildings)
-    {
-        const BuildingDef* def = m_config->buildings.findBuildingDef(bb.type);
-        if (def) { total += def->cost; }
-    }
-    return total;
-}
-
-void BlueprintPanel::rebuildButtons()
-{
-    while (m_buttonsLayout->count() > 1)
-    {
-        QLayoutItem* item = m_buttonsLayout->takeAt(0);
-        if (item->widget()) { delete item->widget(); }
-        delete item;
-    }
-    m_blueprintButtons.clear();
-
-    for (int i = 0; i < static_cast<int>(m_blueprints.size()); ++i)
-    {
-        const Blueprint& bp   = m_blueprints[static_cast<std::size_t>(i)];
-        const int        cost = computeBlueprintCost(bp);
-        const QString label   = bp.name + "\n" + tr("%1 Building Blocks").arg(cost);
-
-        QWidget*     row       = new QWidget(m_buttonsContainer);
-        QHBoxLayout* rowLayout = new QHBoxLayout(row);
-        rowLayout->setContentsMargins(0, 0, 0, 0);
-        rowLayout->setSpacing(4);
-
-        QPushButton* btn = new QPushButton(label, row);
-        btn->setCheckable(true);
-        btn->setFixedHeight(48);
-
-        QPushButton* delBtn = new QPushButton("\xc3\x97", row);
-        delBtn->setFixedWidth(28);
-        delBtn->setFixedHeight(48);
-
-        rowLayout->addWidget(btn, 1);
-        rowLayout->addWidget(delBtn, 0);
-
-        m_buttonsLayout->insertWidget(i, row);
-
-        const int capturedIndex = i;
-        connect(btn, &QPushButton::clicked, this, [this, capturedIndex]() {
-            onBlueprintButtonClicked(capturedIndex);
-        });
-        connect(delBtn, &QPushButton::clicked, this, [this, capturedIndex]() {
-            onDeleteBlueprintClicked(capturedIndex);
-        });
-
-        m_blueprintButtons.push_back(btn);
-    }
-
-    refreshButtonStates();
-}
-
-void BlueprintPanel::saveToDisk() const
-{
-    // Persist on shutdown; write errors are silently ignored (REQ-UI-BLUEPRINT-SAVE).
-    const QString path = QCoreApplication::applicationDirPath() + "/blueprints.toml";
-    QFile file(path);
-    if (!file.open(QIODevice::WriteOnly | QIODevice::Text)) { return; }
-    try
-    {
-        const std::string content = BlueprintSerializer::serialize(m_blueprints);
-        file.write(QByteArray::fromStdString(content));
-    }
-    catch (...) {}
-}
-
-void BlueprintPanel::loadFromDisk()
-{
-    // Load at startup (REQ-UI-BLUEPRINT-LOAD). Missing file: start empty, no error.
-    const QString path = QCoreApplication::applicationDirPath() + "/blueprints.toml";
-    QFile file(path);
-    if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) { return; }
-    try
-    {
-        m_blueprints = BlueprintSerializer::deserialize(file.readAll().toStdString());
-    }
-    catch (const std::exception& e)
-    {
-        QMessageBox::critical(this, tr("Load Failed"),
-            tr("Failed to load blueprints:\n%1").arg(e.what()));
-        m_blueprints.clear();
-    }
-}
-
-void BlueprintPanel::refreshButtonStates()
-{
-    // A construction site counts the same as an operational building (REQ-UI-BLUEPRINT-CREATE).
-    m_createBtn->setEnabled(selectionHasPlaceableBuilding(*m_sim, m_selectedBuildingIds));
-
-    const int blocks = m_sim->getBuildingBlocksStock();
-
-    for (int i = 0; i < static_cast<int>(m_blueprintButtons.size()); ++i)
-    {
-        const int  cost      = computeBlueprintCost(m_blueprints[static_cast<std::size_t>(i)]);
-        const bool canAfford = blocks >= cost;
-        m_blueprintButtons[static_cast<std::size_t>(i)]->setEnabled(
-            canAfford || m_activeIndex == i);
-    }
-}
-
-void BlueprintPanel::handleEvent(std::shared_ptr<const SelectionChangedEvent> event)
-{
-    onSelectionChanged(event->ids);
-}
-
-void BlueprintPanel::handleEvent(std::shared_ptr<const BlueprintModeExitedEvent> /*event*/)
-{
-    clearActiveBlueprintButton();
-}
-
-void BlueprintPanel::handleEvent(std::shared_ptr<const TemporaryBlueprintRequestedEvent> /*event*/)
-{
-    // Temporary blueprint (REQ-UI-BLUEPRINT-TEMP): build from the current selection and
-    // enter placement mode without adding it to the list or persisting it. If nothing
-    // player-placeable is selected, do nothing.
-    Blueprint bp = createBlueprintFromSelection();
-    if (bp.buildings.empty()) { return; }
-
-    // No saved blueprint is active while a temporary one is being placed.
-    clearActiveBlueprintButton();
-    EventManager::getInstance()->sendEventImmediately(
-        std::make_shared<BlueprintPlacementRequestedEvent>(std::move(bp)));
-}

src/ui/BlueprintPanel.h

@@ -1,67 +0,0 @@
-#pragma once
-
-#include <optional>
-#include <vector>
-
-#include <QWidget>
-
-#include "Blueprint.h"
-#include "BlueprintModeExitedEvent.h"
-#include "BuildingBlocksChangedEvent.h"
-#include "BuildingId.h"
-#include "EventHandler.h"
-#include "GameConfig.h"
-#include "SelectionChangedEvent.h"
-#include "TemporaryBlueprintRequestedEvent.h"
-#include "Tick.h"
-
-class Simulation;
-class QPushButton;
-class QScrollArea;
-class QVBoxLayout;
-
-class BlueprintPanel : public QWidget,
-                       public CombinedEventHandler<BuildingBlocksChangedEvent,
-                                                   SelectionChangedEvent,
-                                                   BlueprintModeExitedEvent,
-                                                   TemporaryBlueprintRequestedEvent>
-{
-    Q_OBJECT
-
-public:
-    BlueprintPanel(Simulation* sim, const GameConfig* config, QWidget* parent = nullptr);
-    ~BlueprintPanel() override;
-
-private:
-    void handleEvent(std::shared_ptr<const BuildingBlocksChangedEvent> event) override;
-    void handleEvent(std::shared_ptr<const SelectionChangedEvent> event) override;
-    void handleEvent(std::shared_ptr<const BlueprintModeExitedEvent> event) override;
-    void handleEvent(std::shared_ptr<const TemporaryBlueprintRequestedEvent> event) override;
-
-private slots:
-    void onCreateClicked();
-    void onDeleteBlueprintClicked(int index);
-    void onBlueprintButtonClicked(int index);
-
-private:
-    void onSelectionChanged(const std::vector<BuildingId>& ids);
-    void clearActiveBlueprintButton();
-    Blueprint createBlueprintFromSelection() const;
-    int       computeBlueprintCost(const Blueprint& bp) const;
-    void      rebuildButtons();
-    void      refreshButtonStates();
-    void      loadFromDisk();
-    void      saveToDisk() const;
-
-    // The simulation is the single source of truth for the block stock; the
-    // change event is only a refresh signal.
-    Simulation*               m_sim;
-    const GameConfig*         m_config;
-    std::vector<BuildingId>     m_selectedBuildingIds;
-    std::optional<int>        m_activeIndex;  // nullopt = no blueprint selected
-    std::vector<Blueprint>    m_blueprints;
-    std::vector<QPushButton*> m_blueprintButtons;
-    QPushButton*              m_createBtn;
-    QWidget*                  m_buttonsContainer;
-    QVBoxLayout*              m_buttonsLayout;
-};

src/ui/BlueprintSelectionDialog.cpp

@@ -0,0 +1,331 @@
+#include "BlueprintSelectionDialog.h"
+
+#include <cstddef>
+#include <vector>
+
+#include <QChar>
+#include <QColor>
+#include <QFont>
+#include <QFontMetrics>
+#include <QFrame>
+#include <QGridLayout>
+#include <QGuiApplication>
+#include <QHBoxLayout>
+#include <QIcon>
+#include <QLabel>
+#include <QLayoutItem>
+#include <QPainter>
+#include <QPalette>
+#include <QPixmap>
+#include <QPoint>
+#include <QPushButton>
+#include <QRect>
+#include <QScrollArea>
+#include <QSize>
+#include <QString>
+#include <QStyle>
+#include <QVBoxLayout>
+
+#include "Blueprint.h"
+#include "BlueprintLibrary.h"
+#include "IconCaption.h"
+#include "ItemIconCache.h"
+
+namespace
+{
+    // Fixed at two, per REQ-UI-BLUEPRINT-DIALOG; the grid scrolls rather than reflowing.
+    const int kGridColumnCount = 2;
+
+    // Card geometry. Every card is the same size so the grid stays even
+    // (REQ-UI-BLUEPRINT-CARD); the width is chosen to fit a name and a short contents
+    // line, and the height follows from three text rows.
+    const int kCardWidthPx    = 220;
+    const int kCardPaddingPx  = 10;
+    const int kCardRowGapPx   = 4;
+
+    // Side length of the per-card delete icon and of the dialog's close button.
+    const int kSmallButtonSizePx = 22;
+
+    // Spacing between cards, and the dialog's own content margin.
+    const int kSpacingPx = 8;
+
+    // Card rows visible before the grid scrolls. The half row is deliberate: a cut-off
+    // card reads as "there is more below" at a glance.
+    const double kVisibleRowCount = 2.5;
+
+    // U+00D7 MULTIPLICATION SIGN, the close and delete glyph. Written as a code point
+    // because the sources are not guaranteed to be read as UTF-8 by every compiler.
+    const QChar kCrossGlyph(0x00D7);
+
+    // Inner size of a card's composed face: the name row, the contents row, and the
+    // cost row, plus the gap above the cost.
+    QSize getCardFaceSize(const QFont& font)
+    {
+        const int rowHeight = QFontMetrics(font).height();
+        return QSize(kCardWidthPx - 2 * kCardPaddingPx, rowHeight * 3 + kCardRowGapPx);
+    }
+
+    QSize getCardSize(const QFont& font)
+    {
+        const QSize faceSize = getCardFaceSize(font);
+        return QSize(faceSize.width()  + 2 * kCardPaddingPx,
+                     faceSize.height() + 2 * kCardPaddingPx);
+    }
+
+    // One card face: the blueprint name, its contents line below in a dimmed color,
+    // and the cost with its block icon at the bottom (REQ-UI-BLUEPRINT-CARD). The three
+    // are composed into a single pixmap because a QPushButton holds only one icon --
+    // the same device the build button faces use.
+    QPixmap composeCardFace(const QString& name, const QString& contents,
+                            const QPixmap& cost, const QFont& font,
+                            const QColor& textColor, const QColor& dimColor,
+                            const QSize& faceSize)
+    {
+        const QFontMetrics metrics(font);
+        const int rowHeight = metrics.height();
+
+        const qreal dpr = qApp ? qApp->devicePixelRatio() : 1.0;
+        QPixmap face(static_cast<int>(faceSize.width()  * dpr),
+                     static_cast<int>(faceSize.height() * dpr));
+        face.setDevicePixelRatio(dpr);
+        face.fill(Qt::transparent);
+
+        QPainter painter(&face);
+        painter.setRenderHint(QPainter::Antialiasing, true);
+        painter.setRenderHint(QPainter::SmoothPixmapTransform, true);
+        painter.setFont(font);
+
+        // Both text rows are elided rather than wrapped or shrunk, so a long name or a
+        // many-typed blueprint cannot change a card's height (REQ-UI-BLUEPRINT-CARD).
+        painter.setPen(textColor);
+        painter.drawText(QRect(0, 0, faceSize.width(), rowHeight),
+                         Qt::AlignLeft | Qt::AlignVCenter,
+                         metrics.elidedText(name, Qt::ElideRight, faceSize.width()));
+
+        painter.setPen(dimColor);
+        painter.drawText(QRect(0, rowHeight, faceSize.width(), rowHeight),
+                         Qt::AlignLeft | Qt::AlignVCenter,
+                         metrics.elidedText(contents, Qt::ElideRight, faceSize.width()));
+
+        const QSize costSize = getLogicalSize(cost);
+        painter.drawPixmap(0, faceSize.height() - costSize.height(), cost);
+        return face;
+    }
+
+    // A composed card face and the size to show it at; the button needs both, and only
+    // the composer knows the size it arrived at.
+    struct CardFace { QIcon icon; QSize size; };
+
+    // The two-mode face of one card. The modes differ only in the text color, so an
+    // unaffordable card greys itself when Qt swaps the pixmap on the disabled button
+    // (REQ-UI-BLUEPRINT-CARD, consistent with REQ-UI-BUILD-DISABLED).
+    CardFace buildCardFace(const QString& name, const QString& contents, int cost,
+                           const QPixmap& blockIcon, const QFont& font,
+                           const QPalette& palette)
+    {
+        const QSize  faceSize = getCardFaceSize(font);
+        const QColor dimColor = palette.color(QPalette::Disabled, QPalette::ButtonText);
+
+        CardFace result;
+        for (QIcon::Mode mode : { QIcon::Normal, QIcon::Disabled })
+        {
+            const QColor textColor = palette.color(
+                (mode == QIcon::Normal) ? QPalette::Active : QPalette::Disabled,
+                QPalette::ButtonText);
+            // The cost reads exactly like the header stock and the build button costs:
+            // the number, then the block icon in place of a trailing "Blocks"
+            // (REQ-UI-BLOCKS-ICON). A null icon leaves the bare number.
+            const QPixmap costPixmap =
+                renderCaptionWithIcon(QString::number(cost), blockIcon, font, textColor);
+            const QPixmap face = composeCardFace(name, contents, costPixmap, font,
+                                                 textColor, dimColor, faceSize);
+            result.icon.addPixmap(face, mode);
+            result.size = result.size.expandedTo(getLogicalSize(face));
+        }
+        return result;
+    }
+}
+
+BlueprintSelectionDialog::BlueprintSelectionDialog(BlueprintLibrary* library,
+                                                   ItemIconCache* itemIcons,
+                                                   QWidget* parent)
+    : QDialog(parent)
+    , m_library(library)
+    , m_itemIcons(itemIcons)
+{
+    setWindowTitle(tr("Blueprints"));
+    setModal(true);
+    // 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 selection panel.
+    setWindowFlags(Qt::Dialog | Qt::FramelessWindowHint);
+    setAttribute(Qt::WA_StyledBackground, true);
+    setStyleSheet(QStringLiteral(
+        "BlueprintSelectionDialog { background-color: palette(window);"
+        " border: 1px solid palette(mid); }"));
+
+    QVBoxLayout* mainLayout = new QVBoxLayout(this);
+    mainLayout->setContentsMargins(kSpacingPx, kSpacingPx, kSpacingPx, kSpacingPx);
+    mainLayout->setSpacing(kSpacingPx);
+
+    QHBoxLayout* headerLayout = new QHBoxLayout();
+    headerLayout->setSpacing(kSpacingPx);
+
+    QLabel* titleLabel = new QLabel(tr("Blueprints"), this);
+    QFont headerFont = titleLabel->font();
+    headerFont.setBold(true);
+    titleLabel->setFont(headerFont);
+    headerLayout->addWidget(titleLabel);
+
+    // Dimmed and bold, the treatment the build button hotkey badges use, so the
+    // shortcut reads as a reminder rather than a second title (REQ-UI-BUILD-COST).
+    QLabel* hotkeyBadge = new QLabel(tr("Ctrl+V"), this);
+    hotkeyBadge->setFont(headerFont);
+    QPalette badgePalette = hotkeyBadge->palette();
+    badgePalette.setColor(hotkeyBadge->foregroundRole(),
+                          palette().color(QPalette::Disabled, QPalette::WindowText));
+    hotkeyBadge->setPalette(badgePalette);
+    headerLayout->addWidget(hotkeyBadge);
+
+    headerLayout->addStretch();
+
+    QPushButton* closeButton = new QPushButton(QString(kCrossGlyph), this);
+    closeButton->setFixedSize(kSmallButtonSizePx, kSmallButtonSizePx);
+    closeButton->setToolTip(tr("Close"));
+    connect(closeButton, &QPushButton::clicked, this, &QDialog::reject);
+    headerLayout->addWidget(closeButton);
+
+    mainLayout->addLayout(headerLayout);
+
+    QScrollArea* scrollArea = new QScrollArea(this);
+    scrollArea->setWidgetResizable(true);
+    scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    scrollArea->setFrameShape(QFrame::NoFrame);
+
+    m_gridContainer = new QWidget(scrollArea);
+    m_grid = new QGridLayout(m_gridContainer);
+    m_grid->setContentsMargins(0, 0, 0, 0);
+    m_grid->setSpacing(kSpacingPx);
+    m_grid->setAlignment(Qt::AlignTop | Qt::AlignLeft);
+    scrollArea->setWidget(m_gridContainer);
+    mainLayout->addWidget(scrollArea, 1);
+
+    rebuildGrid();
+
+    // Fixed size (REQ-UI-BLUEPRINT-DIALOG), sized to show kVisibleRowCount card rows.
+    const QSize cardSize = getCardSize(font());
+    const int gridWidth  = kGridColumnCount * cardSize.width()
+        + (kGridColumnCount - 1) * kSpacingPx;
+    const int gridHeight = static_cast<int>(
+        cardSize.height() * kVisibleRowCount + kSpacingPx * (kVisibleRowCount - 1.0));
+    setFixedSize(gridWidth + style()->pixelMetric(QStyle::PM_ScrollBarExtent)
+                     + 2 * kSpacingPx,
+                 gridHeight + kSmallButtonSizePx + 3 * kSpacingPx);
+
+    // A frameless dialog does not get Qt's automatic centering on its parent.
+    if (parent)
+    {
+        const QRect parentRect = parent->window()->geometry();
+        move(parentRect.center() - QPoint(width() / 2, height() / 2));
+    }
+}
+
+std::optional<int> BlueprintSelectionDialog::getChosenIndex() const
+{
+    return m_chosenIndex;
+}
+
+void BlueprintSelectionDialog::rebuildGrid()
+{
+    // deleteLater, not delete: this runs from a delete button's own clicked signal, and
+    // destroying that button inside its emission would leave Qt holding a dangling
+    // sender. hide() makes the removal immediate all the same.
+    while (QLayoutItem* item = m_grid->takeAt(0))
+    {
+        if (item->widget())
+        {
+            item->widget()->hide();
+            item->widget()->deleteLater();
+        }
+        delete item;
+    }
+
+    const std::vector<Blueprint>& blueprints = m_library->getBlueprints();
+    if (blueprints.empty())
+    {
+        QLabel* emptyLabel = new QLabel(
+            tr("No blueprints yet.\n\nSelect one or more buildings and press Ctrl+C "
+               "to save them as a blueprint."),
+            m_gridContainer);
+        emptyLabel->setAlignment(Qt::AlignCenter);
+        emptyLabel->setWordWrap(true);
+        m_grid->addWidget(emptyLabel, 0, 0, 1, kGridColumnCount);
+        return;
+    }
+
+    // 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->getInlineIcon(kBlockItemId, font());
+
+    const QSize cardSize = getCardSize(font());
+
+    for (int i = 0; i < static_cast<int>(blueprints.size()); ++i)
+    {
+        const Blueprint& blueprint = blueprints[static_cast<std::size_t>(i)];
+        const CardFace   face      = buildCardFace(
+            blueprint.name, m_library->getContentsSummary(i), m_library->getCost(i),
+            blockIcon, font(), palette());
+
+        QWidget* card = new QWidget(m_gridContainer);
+        card->setFixedSize(cardSize);
+
+        QVBoxLayout* cardLayout = new QVBoxLayout(card);
+        cardLayout->setContentsMargins(0, 0, 0, 0);
+
+        QPushButton* body = new QPushButton(card);
+        body->setIcon(face.icon);
+        body->setIconSize(face.size);
+        // An unaffordable card is greyed and does not respond, but its delete icon
+        // stays live (REQ-UI-BLUEPRINT-CARD).
+        body->setEnabled(m_library->getCanAfford(i));
+        cardLayout->addWidget(body);
+
+        // A sibling of the body rather than one of its children, and outside the
+        // layout: Qt disables a widget's children along with it, and the delete icon
+        // must stay enabled on an unaffordable card (REQ-UI-BLUEPRINT-DELETE).
+        QPushButton* deleteButton = new QPushButton(QString(kCrossGlyph), card);
+        deleteButton->setFixedSize(kSmallButtonSizePx, kSmallButtonSizePx);
+        deleteButton->setToolTip(tr("Delete blueprint"));
+        deleteButton->move(cardSize.width()  - kSmallButtonSizePx - kCardPaddingPx / 2,
+                           cardSize.height() - kSmallButtonSizePx - kCardPaddingPx / 2);
+        deleteButton->raise();
+
+        m_grid->addWidget(card, i / kGridColumnCount, i % kGridColumnCount);
+
+        const int index = i;
+        connect(body, &QPushButton::clicked, this, [this, index]()
+        {
+            onCardClicked(index);
+        });
+        connect(deleteButton, &QPushButton::clicked, this, [this, index]()
+        {
+            onDeleteClicked(index);
+        });
+    }
+}
+
+void BlueprintSelectionDialog::onCardClicked(int index)
+{
+    // Placement mode is entered by the caller once the dialog has closed
+    // (REQ-UI-BLUEPRINT-CARD).
+    m_chosenIndex = index;
+    accept();
+}
+
+void BlueprintSelectionDialog::onDeleteClicked(int index)
+{
+    // No confirmation prompt, and the dialog stays open (REQ-UI-BLUEPRINT-DELETE).
+    m_library->remove(index);
+    rebuildGrid();
+}

src/ui/BlueprintSelectionDialog.h

@@ -0,0 +1,42 @@
+#pragma once
+
+#include <optional>
+
+#include <QDialog>
+
+class BlueprintLibrary;
+class ItemIconCache;
+class QGridLayout;
+class QWidget;
+
+// The blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG): a frameless modal panel
+// showing every saved blueprint as a card in a scrolling two-column grid. The caller
+// pauses the game and raises the dim overlay while it is open.
+//
+// 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.
+class BlueprintSelectionDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    // Neither the library nor the icon cache is owned; both outlive the dialog.
+    BlueprintSelectionDialog(BlueprintLibrary* library, ItemIconCache* itemIcons,
+                             QWidget* parent = nullptr);
+
+    std::optional<int> getChosenIndex() const;
+
+private:
+    void rebuildGrid();
+    void onCardClicked(int index);
+    void onDeleteClicked(int index);
+
+    BlueprintLibrary*  m_library;
+    ItemIconCache*     m_itemIcons;
+    QWidget*           m_gridContainer;
+    QGridLayout*       m_grid;
+    std::optional<int> m_chosenIndex;  // nullopt = dismissed without picking
+};

src/ui/BuildButtonBar.cpp

@@ -0,0 +1,411 @@
+#include "BuildButtonBar.h"
+
+#include <string>
+
+#include <QColor>
+#include <QFont>
+#include <QFontMetrics>
+#include <QGuiApplication>
+#include <QHBoxLayout>
+#include <QIcon>
+#include <QPainter>
+#include <QPalette>
+#include <QPixmap>
+#include <QPushButton>
+#include <QRect>
+#include <QSignalMapper>
+#include <QSize>
+#include <QString>
+
+#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"
+#include "Simulation.h"
+
+namespace
+{
+    // Size the SVG chips are drawn at on a button face, in device-independent pixels.
+    const QSize kIconSize(32, 32);
+
+    // Minimum width of a button face. The building-type buttons all come out at this
+    // width, so the row is uniform; a face whose caption is wider than this — the
+    // Deconstruct button's name — grows to fit rather than clipping
+    // (REQ-UI-DECONSTRUCT-BUTTON).
+    const int kFaceMinWidthPx = 48;
+
+    // Gap between the last building button and the Deconstruct button, which toggles
+    // a mode rather than selecting a building type (REQ-UI-DECONSTRUCT-BUTTON).
+    const int kDeconstructGapPx = 16;
+
+    // Distance from the bar to the bottom edge of the game world view
+    // (REQ-UI-BUILD-BAR).
+    const int kBottomMarginPx = 8;
+
+    // Gap between the chip icon and the cost line on a button face.
+    const int kFaceGapPx = 2;
+
+    // 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(BuildingIconCache& icons, const std::string& iconName)
+    {
+        ChipPixmaps result;
+        result.normal = icons.getChip(iconName, kIconSize.width());
+        result.grey   = icons.getGreyChip(iconName, kIconSize.width());
+        return result;
+    }
+
+    // One button face: the hotkey badge in the top-left corner, the chip icon centered
+    // below it, and the caption — the cost, or the Deconstruct name — centered at the
+    // bottom (REQ-UI-BUILD-COST). The three are composed into a single pixmap because
+    // a QPushButton holds only one icon.
+    QPixmap composeButtonFace(const QString& hotkeyLabel, const QPixmap& chip,
+                              const QPixmap& caption, const QFont& badgeFont,
+                              const QColor& badgeColor)
+    {
+        const QSize chipSize    = getLogicalSize(chip);
+        const QSize captionSize = getLogicalSize(caption);
+        // The badge row is kept even for a building type without a hotkey, so buttons
+        // stay the same height and the row reads as one strip (REQ-UI-BUILD-COST).
+        const int badgeHeight = QFontMetrics(badgeFont).height();
+        const int width  = qMax(kFaceMinWidthPx, qMax(chipSize.width(), captionSize.width()));
+        const int height = badgeHeight + chipSize.height() + kFaceGapPx + captionSize.height();
+
+        const qreal dpr = qApp ? qApp->devicePixelRatio() : 1.0;
+        QPixmap face(static_cast<int>(width * dpr), static_cast<int>(height * dpr));
+        face.setDevicePixelRatio(dpr);
+        face.fill(Qt::transparent);
+
+        QPainter painter(&face);
+        painter.setRenderHint(QPainter::Antialiasing, true);
+        painter.setRenderHint(QPainter::SmoothPixmapTransform, true);
+        if (!hotkeyLabel.isEmpty())
+        {
+            painter.setFont(badgeFont);
+            painter.setPen(badgeColor);
+            painter.drawText(QRect(0, 0, width, badgeHeight),
+                             Qt::AlignLeft | Qt::AlignVCenter, hotkeyLabel);
+        }
+        painter.drawPixmap((width - chipSize.width()) / 2, badgeHeight, chip);
+        painter.drawPixmap((width - captionSize.width()) / 2,
+                           badgeHeight + chipSize.height() + kFaceGapPx, caption);
+        return face;
+    }
+
+    // A composed button face and the size to show it at; the button needs both, and
+    // only the composer knows the size it arrived at.
+    struct ButtonFace { QIcon icon; QSize size; };
+
+    // The two-mode face of one build button. The modes differ only in the chip variant
+    // and the text color, so a disabled (unaffordable) button greys itself when Qt
+    // swaps the pixmap, with no extra work in updateAffordability()
+    // (REQ-UI-BUILD-DISABLED).
+    ButtonFace buildButtonFace(const ChipPixmaps& chip, const QString& hotkeyLabel,
+                               const QString& name, const QString& captionText,
+                               const QPixmap& blockIcon, const QFont& font,
+                               const QPalette& palette)
+    {
+        // Full button size and bold: at a smaller size the badge was hard to read and
+        // its arrow glyph illegible. It stays dimmed in both modes instead, so it
+        // reads as a reminder without competing with the cost.
+        QFont badgeFont = font;
+        badgeFont.setBold(true);
+        const QColor badgeColor = palette.color(QPalette::Disabled, QPalette::ButtonText);
+
+        ButtonFace result;
+        for (QIcon::Mode mode : { QIcon::Normal, QIcon::Disabled })
+        {
+            const bool enabled = (mode == QIcon::Normal);
+            const QColor textColor = palette.color(
+                enabled ? QPalette::Active : QPalette::Disabled, QPalette::ButtonText);
+            const QPixmap& chipPixmap = enabled ? chip.normal : chip.grey;
+            // A missing "<id>.svg" puts the building name where the chip would be, so
+            // the button stays identifiable in an icon-only bar (REQ-UI-BUILD-ICON).
+            const QPixmap middle = chipPixmap.isNull()
+                ? renderCaptionWithIcon(name, QPixmap(), font, textColor)
+                : chipPixmap;
+            const QPixmap caption =
+                renderCaptionWithIcon(captionText, blockIcon, font, textColor);
+            const QPixmap face =
+                composeButtonFace(hotkeyLabel, middle, caption, badgeFont, badgeColor);
+            result.icon.addPixmap(face, mode);
+            // Both modes compose to the same size; keeping the larger is only a guard
+            // against a fallback name caption widening one of them.
+            result.size = result.size.expandedTo(getLogicalSize(face));
+        }
+        return result;
+    }
+
+}
+
+
+BuildButtonBar::BuildButtonBar(Simulation* sim, const GameConfig* config,
+                               BuildingIconCache* buildingIcons,
+                               ItemIconCache* itemIcons, QWidget* parent)
+    : QWidget(parent)
+    , m_sim(sim)
+    , m_config(config)
+    , 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 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(
+        "BuildButtonBar { background-color: palette(window);"
+        " border: 1px solid palette(mid); border-radius: 4px; }"));
+
+    QHBoxLayout* layout = new QHBoxLayout(this);
+    layout->setSpacing(4);
+    layout->setContentsMargins(6, 4, 6, 4);
+
+    QSignalMapper* mapper = new QSignalMapper(this);
+
+    // 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->getInlineIcon(kBlockItemId, font());
+
+    for (const BuildingDef& def : config->buildings.buildings)
+    {
+        if (!def.playerPlaceable)
+        {
+            continue;
+        }
+        // Tunnel Entry and Tunnel Exit share a single "Tunnel" button; the exit is
+        // reached through the unified tunnel build mode, not its own button
+        // (REQ-BLD-TUNNEL-MODE, REQ-UI-BUILD-BAR). Both stay player-placeable so
+        // blueprints and cost totals still account for exits.
+        if (def.type == BuildingType::TunnelExit)
+        {
+            continue;
+        }
+        m_types.push_back(def.type);
+        m_costs[def.type] = def.cost;
+
+        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 ButtonFace face = buildButtonFace(
+            loadChipPixmaps(*m_buildingIcons, def.id),
+            InputMapper::getBuildHotkeyLabel(def.type), name,
+            QString::number(def.cost), blockIcon, font(), palette());
+
+        QPushButton* btn = new QPushButton(this);
+        btn->setIcon(face.icon);
+        btn->setIconSize(face.size);
+        btn->setCheckable(true);
+        // The button face carries no name (REQ-UI-BUILD-COST), so the tooltip always
+        // leads with it and adds the config description when there is one
+        // (REQ-UI-BUILD-TOOLTIP).
+        btn->setToolTip(def.tooltip
+            ? QStringLiteral("%1\n%2").arg(name, QString::fromStdString(*def.tooltip))
+            : name);
+        layout->addWidget(btn);
+
+        const int idx = static_cast<int>(m_buttons.size());
+        m_buttons.push_back(btn);
+        mapper->setMapping(btn, idx);
+        connect(btn, &QPushButton::clicked, mapper, qOverload<>(&QSignalMapper::map));
+    }
+    connect(mapper, qOverload<int>(&QSignalMapper::mapped), this, &BuildButtonBar::onBuildButton);
+
+    // Set apart from the building-type buttons by a gap, because it toggles a mode
+    // rather than selecting a building type (REQ-UI-DECONSTRUCT-BUTTON). A fixed
+    // spacer rather than a stretch: the bar is sized to its contents, so there is no
+    // right edge for a stretch to push against.
+    layout->addSpacing(kDeconstructGapPx);
+
+    // 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(*m_buildingIcons, "deconstruct"),
+        QStringLiteral("Q"), tr("Deconstruct"), tr("Deconstruct"), QPixmap(),
+        font(), palette());
+
+    m_deconstructButton = new QPushButton(this);
+    m_deconstructButton->setCheckable(true);
+    m_deconstructButton->setIcon(deconstructFace.icon);
+    m_deconstructButton->setIconSize(deconstructFace.size);
+    // Refund tooltip composed from world.refund_percentage (REQ-UI-DECONSTRUCT-BUTTON,
+    // REQ-BLD-DECONSTRUCT). A finished building refunds the configured percentage; a
+    // construction site removed before it is built is refunded in full. When the
+    // percentage is 100% both cases coincide, so the tooltip is simplified to one case.
+    const int refundPercentage = m_config->world.refundPercentage;
+    const QString deconstructTooltip = (refundPercentage >= 100)
+        ? tr("Deconstruct buildings. Refunds %1% of the building block cost.")
+              .arg(refundPercentage)
+        : tr("Deconstruct buildings. A finished building refunds %1% of its building "
+             "block cost once removed; a construction site removed before it is built "
+             "is refunded in full.")
+              .arg(refundPercentage);
+    m_deconstructButton->setToolTip(deconstructTooltip);
+    layout->addWidget(m_deconstructButton);
+    connect(m_deconstructButton, &QPushButton::clicked, this, [this]() {
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<DeconstructModeToggleRequestedEvent>());
+    });
+
+    updateVisibility();
+    registerForEvents();
+}
+
+BuildButtonBar::~BuildButtonBar()
+{
+    unregisterForEvents();
+}
+
+void BuildButtonBar::placeIn(const QRect& viewRect,
+                             const std::vector<QRect>& /*occupiedRects*/)
+{
+    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()
+{
+    if (m_activeIndex)
+    {
+        m_buttons[*m_activeIndex]->setChecked(false);
+    }
+    m_activeIndex.reset();
+}
+
+void BuildButtonBar::updateAffordability()
+{
+    const int buildingBlocks = m_sim->getBuildingBlocksStock();
+
+    // If the currently selected tool can no longer be afforded, exit builder mode
+    // before recomputing button states so it does not stay selected. Clearing the
+    // active index first lets the loop below disable the now-unaffordable button.
+    if (m_activeIndex)
+    {
+        const BuildingType activeType = m_types[*m_activeIndex];
+        const std::map<BuildingType, int>::const_iterator it = m_costs.find(activeType);
+        const int cost = (it != m_costs.end()) ? it->second : 0;
+        if (buildingBlocks < cost)
+        {
+            clearActiveButton();
+            EventManager::getInstance()->sendEventImmediately(
+                std::make_shared<ExitBuilderModeRequestedEvent>());
+        }
+    }
+
+    for (std::size_t i = 0; i < m_buttons.size(); ++i)
+    {
+        const BuildingType type = m_types[i];
+        const std::map<BuildingType, int>::const_iterator it = m_costs.find(type);
+        const int cost = (it != m_costs.end()) ? it->second : 0;
+        m_buttons[i]->setEnabled(buildingBlocks >= cost || m_activeIndex == i);
+    }
+}
+
+void BuildButtonBar::updateVisibility()
+{
+    // A locked building type's button is hidden until its unlock group is awarded
+    // (REQ-LOCK-BUILDING). Buttons keep their index so hotkeys/affordability stay
+    // stable; they simply appear once the type is unlocked.
+    for (std::size_t i = 0; i < m_buttons.size(); ++i)
+    {
+        m_buttons[i]->setVisible(m_sim->isBuildingUnlocked(m_types[i]));
+    }
+    // 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)
+{
+    if (index < 0 || index >= static_cast<int>(m_buttons.size()))
+    {
+        return;
+    }
+    const std::size_t idx = static_cast<std::size_t>(index);
+
+    if (m_activeIndex == idx)
+    {
+        clearActiveButton();
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<ExitBuilderModeRequestedEvent>());
+        return;
+    }
+
+    if (m_activeIndex)
+    {
+        m_buttons[*m_activeIndex]->setChecked(false);
+    }
+
+    m_activeIndex = idx;
+    m_buttons[idx]->setChecked(true);
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<BuildingTypeSelectedEvent>(m_types[idx]));
+}
+
+void BuildButtonBar::handleEvent(std::shared_ptr<const BuilderModeExitedEvent> /*event*/)
+{
+    clearActiveButton();
+}
+
+void BuildButtonBar::handleEvent(std::shared_ptr<const BuildingBlocksChangedEvent> /*event*/)
+{
+    updateAffordability();
+}
+
+void BuildButtonBar::handleEvent(std::shared_ptr<const UnlockedBuildingsChangedEvent> /*event*/)
+{
+    updateVisibility();
+    updateAffordability();
+}
+
+void BuildButtonBar::handleEvent(std::shared_ptr<const DeconstructModeChangedEvent> event)
+{
+    m_deconstructButton->setChecked(event->active);
+}
+
+void BuildButtonBar::handleEvent(std::shared_ptr<const BuildHotkeyPressedEvent> event)
+{
+    for (std::size_t i = 0; i < m_types.size(); ++i)
+    {
+        if (m_types[i] == event->type)
+        {
+            // Equivalent to clicking the build button: a disabled (unaffordable) or
+            // hidden (locked, REQ-LOCK-BUILDING) button cannot be clicked, so the
+            // hotkey is likewise inert.
+            if (m_buttons[i]->isEnabled() && m_buttons[i]->isVisible())
+            {
+                onBuildButton(static_cast<int>(i));
+            }
+            return;
+        }
+    }
+}

src/ui/BuildButtonBar.h

@@ -0,0 +1,88 @@
+#pragma once
+
+#include <map>
+#include <memory>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include <QRect>
+#include <QWidget>
+
+#include "BuilderModeExitedEvent.h"
+#include "BuildHotkeyPressedEvent.h"
+#include "BuildingBlocksChangedEvent.h"
+#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 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,
+                                                   BuildingBlocksChangedEvent,
+                                                   UnlockedBuildingsChangedEvent>
+{
+    Q_OBJECT
+
+public:
+    // 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,
+                   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). 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();
+
+private:
+    // Re-evaluates which build buttons are enabled from the current building block
+    // stock (read from the simulation). If the currently selected tool can no longer
+    // be afforded, it exits builder mode so the button does not stay selected.
+    void updateAffordability();
+
+    // Re-evaluates which build buttons are visible from the current per-building
+    // unlock state (REQ-LOCK-BUILDING); a locked building type's button is hidden.
+    void updateVisibility();
+
+    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;
+    void handleEvent(std::shared_ptr<const BuildingBlocksChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const UnlockedBuildingsChangedEvent> event) override;
+
+private slots:
+    void onBuildButton(int index);
+
+private:
+    Simulation*                      m_sim;
+    const GameConfig*                m_config;
+    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;
+};

src/ui/BuildButtonGrid.cpp

@@ -1,419 +0,0 @@
-#include "BuildButtonGrid.h"
-
-#include <string>
-
-#include <QByteArray>
-#include <QColor>
-#include <QFile>
-#include <QFontMetrics>
-#include <QGridLayout>
-#include <QIcon>
-#include <QPainter>
-#include <QPaintEvent>
-#include <QPalette>
-#include <QPixmap>
-#include <QPushButton>
-#include <QRect>
-#include <QRegularExpression>
-#include <QSignalMapper>
-#include <QSize>
-#include <QString>
-#include <QSvgRenderer>
-
-#include "BuildingType.h"
-#include "BuildingTypeSelectedEvent.h"
-#include "DeconstructModeToggleRequestedEvent.h"
-#include "DisplayName.h"
-#include "EventManager.h"
-#include "ExitBuilderModeRequestedEvent.h"
-#include "ItemIconCache.h"
-#include "Simulation.h"
-
-namespace
-{
-    // Pixel size the SVG chips are rasterized at; downscaled to the button icon size.
-    const int kIconRenderSize = 64;
-    const QSize kIconSize(28, 28);
-
-    QPixmap renderChip(const QByteArray& svg)
-    {
-        QSvgRenderer renderer(svg);
-        QPixmap pixmap(kIconRenderSize, kIconRenderSize);
-        pixmap.fill(Qt::transparent);
-        QPainter painter(&pixmap);
-        renderer.render(&painter);
-        return pixmap;
-    }
-
-    // Builds a build-button icon from a "<id>.svg" chip file. The returned QIcon also
-    // carries a Disabled-mode pixmap whose chip background is recolored grey, so an
-    // unaffordable (disabled) button shows the grey variant automatically
-    // (REQ-UI-BUILD-DISABLED) without any extra work in updateAffordability().
-    QIcon loadBuildingIcon(const QString& path)
-    {
-        QFile file(path);
-        if (!file.open(QIODevice::ReadOnly))
-        {
-            return QIcon();
-        }
-        const QByteArray svg = file.readAll();
-
-        QIcon icon;
-        icon.addPixmap(renderChip(svg), QIcon::Normal);
-
-        // 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\""));
-        }
-        icon.addPixmap(renderChip(greyed.toUtf8()), QIcon::Disabled);
-        return icon;
-    }
-
-    // Normal and grey-background chip pixmaps for a "<id>.svg" file, using the same
-    // recolor rule as loadBuildingIcon. Empty pixmaps if the file cannot be read.
-    struct ChipPixmaps { QPixmap normal; QPixmap grey; };
-    ChipPixmaps loadChipPixmaps(const QString& path)
-    {
-        QFile file(path);
-        if (!file.open(QIODevice::ReadOnly)) { return {}; }
-        const QByteArray svg = file.readAll();
-
-        ChipPixmaps result;
-        result.normal = renderChip(svg);
-        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());
-        return result;
-    }
-
-    // A build button that paints its own face — chip icon at the left, the building
-    // name above the cost, and the building_block item icon after the cost number in
-    // place of the "Blocks" word (REQ-UI-BUILD-COST, REQ-UI-BUILD-ICON). Custom paint
-    // (rather than the native icon+text) is needed because a QPushButton holds only
-    // one icon; this stays adaptive to the button width and greys itself when the
-    // button is disabled/unaffordable (REQ-UI-BUILD-DISABLED).
-    class BuildButton : public QPushButton
-    {
-    public:
-        BuildButton(const ChipPixmaps& chip, const QString& name,
-                    const QString& costText, const QPixmap& blockIcon, QWidget* parent)
-            : QPushButton(parent)
-            , m_chip(chip)
-            , m_name(name)
-            , m_costText(costText)
-            , m_blockIcon(blockIcon)
-        {
-        }
-
-    protected:
-        void paintEvent(QPaintEvent* event) override
-        {
-            QPushButton::paintEvent(event);  // frame, checked/hover state
-
-            QPainter painter(this);
-            painter.setRenderHint(QPainter::Antialiasing, true);
-            painter.setRenderHint(QPainter::SmoothPixmapTransform, true);
-
-            const bool on = isEnabled();
-            const QRect area = rect().adjusted(6, 4, -6, -4);
-            const int chipSize = kIconSize.width();
-            const QPixmap& chip = on ? m_chip.normal : m_chip.grey;
-            if (!chip.isNull())
-            {
-                painter.drawPixmap(
-                    QRect(area.x(), area.y() + (area.height() - chipSize) / 2,
-                          chipSize, chipSize), chip);
-            }
-
-            const QRect textArea(area.x() + chipSize + 6, area.y(),
-                                 area.width() - chipSize - 6, area.height());
-            const QFontMetrics metrics(font());
-            const int lineHeight = metrics.height();
-            painter.setFont(font());
-            painter.setPen(palette().color(on ? QPalette::Active : QPalette::Disabled,
-                                           QPalette::ButtonText));
-
-            // Name fills everything above the bottom cost line (word-wrapped).
-            painter.drawText(
-                QRect(textArea.x(), textArea.y(),
-                      textArea.width(), textArea.height() - lineHeight),
-                Qt::AlignLeft | Qt::AlignVCenter | Qt::TextWordWrap, m_name);
-
-            // Cost line: "<n>" then the block icon (or "<n> Blocks" when no icon).
-            const int costY = textArea.bottom() - lineHeight + 1;
-            if (m_blockIcon.isNull())
-            {
-                painter.drawText(
-                    QRect(textArea.x(), costY, textArea.width(), lineHeight),
-                    Qt::AlignLeft | Qt::AlignVCenter,
-                    QObject::tr("%1 Blocks").arg(m_costText));
-                return;
-            }
-            const int costWidth = metrics.horizontalAdvance(m_costText);
-            painter.drawText(QRect(textArea.x(), costY, costWidth, lineHeight),
-                             Qt::AlignLeft | Qt::AlignVCenter, m_costText);
-            const qreal iconDpr = m_blockIcon.devicePixelRatio();
-            const int iconW = static_cast<int>(m_blockIcon.width() / iconDpr);
-            const int iconH = static_cast<int>(m_blockIcon.height() / iconDpr);
-            if (!on) { painter.setOpacity(0.45); }
-            painter.drawPixmap(
-                QRect(textArea.x() + costWidth + 4, costY + (lineHeight - iconH) / 2,
-                      iconW, iconH), m_blockIcon);
-        }
-
-    private:
-        ChipPixmaps m_chip;
-        QString     m_name;
-        QString     m_costText;
-        QPixmap     m_blockIcon;
-    };
-}
-
-
-BuildButtonGrid::BuildButtonGrid(Simulation* sim, const GameConfig* config,
-                                 const std::string& iconDir,
-                                 ItemIconCache* itemIcons, QWidget* parent)
-    : QWidget(parent)
-    , m_sim(sim)
-    , m_config(config)
-    , m_iconDir(iconDir)
-    , m_itemIcons(itemIcons)
-{
-    QGridLayout* layout = new QGridLayout(this);
-    layout->setSpacing(4);
-    layout->setContentsMargins(4, 4, 4, 4);
-
-    QSignalMapper* mapper = new QSignalMapper(this);
-    int col = 0;
-    int row = 0;
-    const int kCols = 3;
-
-    // Block icon shown in each button's cost line (REQ-UI-BUILD-COST); null when no
-    // building_block icon exists, in which case buttons fall back to text costs.
-    const bool hasBlockIcon = m_itemIcons->hasIcon("building_block");
-    const QPixmap blockIcon = hasBlockIcon
-        ? m_itemIcons->getPixmap("building_block", QFontMetrics(font()).height())
-        : QPixmap();
-
-    for (const BuildingDef& def : config->buildings.buildings)
-    {
-        if (!def.playerPlaceable)
-        {
-            continue;
-        }
-        // Tunnel Entry and Tunnel Exit share a single "Tunnel" button; the exit is
-        // reached through the unified tunnel build mode, not its own button
-        // (REQ-BLD-TUNNEL-MODE, REQ-UI-BUILD-GRID). Both stay player-placeable so
-        // blueprints and cost totals still account for exits.
-        if (def.type == BuildingType::TunnelExit)
-        {
-            continue;
-        }
-        m_types.push_back(def.type);
-        m_costs[def.type] = def.cost;
-
-        const QString name = (def.type == BuildingType::TunnelEntry)
-            ? tr("Tunnel")
-            : QString::fromStdString(toDisplayName(def.id));
-        // Icon file name matches the building id (REQ-UI-BUILD-GRID); Tunnel Entry's
-        // "tunnel_entry.svg" serves the shared Tunnel button.
-        const QString iconPath = QString::fromStdString(m_iconDir) + "/"
-            + QString::fromStdString(def.id) + ".svg";
-
-        QPushButton* btn = nullptr;
-        if (hasBlockIcon)
-        {
-            // Custom-painted button showing the cost with the block icon in place of
-            // the "Blocks" word (REQ-UI-BUILD-COST).
-            btn = new BuildButton(loadChipPixmaps(iconPath), name,
-                                  QString::number(def.cost), blockIcon, this);
-        }
-        else
-        {
-            // Fallback: native chip icon + text cost when no block icon exists.
-            btn = new QPushButton(name + "\n" + tr("%1 Blocks").arg(def.cost), this);
-            btn->setIcon(loadBuildingIcon(iconPath));
-            btn->setIconSize(kIconSize);
-        }
-        btn->setCheckable(true);
-        btn->setFixedHeight(48);
-        if (def.tooltip)
-        {
-            btn->setToolTip(QString::fromStdString(*def.tooltip));
-        }
-        layout->addWidget(btn, row, col);
-
-        const int idx = static_cast<int>(m_buttons.size());
-        m_buttons.push_back(btn);
-        mapper->setMapping(btn, idx);
-        connect(btn, &QPushButton::clicked, mapper, qOverload<>(&QSignalMapper::map));
-
-        ++col;
-        if (col >= kCols)
-        {
-            col = 0;
-            ++row;
-        }
-    }
-    connect(mapper, qOverload<int>(&QSignalMapper::mapped), this, &BuildButtonGrid::onBuildButton);
-
-    m_deconstructButton = new QPushButton(tr("Deconstruct"), this);
-    m_deconstructButton->setCheckable(true);
-    m_deconstructButton->setFixedHeight(48);
-    m_deconstructButton->setIcon(loadBuildingIcon(
-        QString::fromStdString(m_iconDir) + "/deconstruct.svg"));
-    m_deconstructButton->setIconSize(kIconSize);
-    // Refund tooltip composed from world.refund_percentage (REQ-UI-DECONSTRUCT-BUTTON,
-    // REQ-BLD-DECONSTRUCT). A finished building refunds the configured percentage; a
-    // construction site removed before it is built is refunded in full. When the
-    // percentage is 100% both cases coincide, so the tooltip is simplified to one case.
-    const int refundPercentage = m_config->world.refundPercentage;
-    const QString deconstructTooltip = (refundPercentage >= 100)
-        ? tr("Deconstruct buildings. Refunds %1% of the building block cost.")
-              .arg(refundPercentage)
-        : tr("Deconstruct buildings. A finished building refunds %1% of its building "
-             "block cost once removed; a construction site removed before it is built "
-             "is refunded in full.")
-              .arg(refundPercentage);
-    m_deconstructButton->setToolTip(deconstructTooltip);
-    layout->addWidget(m_deconstructButton, row, col);
-    connect(m_deconstructButton, &QPushButton::clicked, this, [this]() {
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<DeconstructModeToggleRequestedEvent>());
-    });
-
-    updateVisibility();
-    registerForEvents();
-}
-
-BuildButtonGrid::~BuildButtonGrid()
-{
-    unregisterForEvents();
-}
-
-void BuildButtonGrid::updateAffordability()
-{
-    const int buildingBlocks = m_sim->getBuildingBlocksStock();
-
-    // If the currently selected tool can no longer be afforded, exit builder mode
-    // before recomputing button states so it does not stay selected. Clearing the
-    // active index first lets the loop below disable the now-unaffordable button.
-    if (m_activeIndex)
-    {
-        const BuildingType activeType = m_types[*m_activeIndex];
-        const std::map<BuildingType, int>::const_iterator it = m_costs.find(activeType);
-        const int cost = (it != m_costs.end()) ? it->second : 0;
-        if (buildingBlocks < cost)
-        {
-            clearActiveButton();
-            EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<ExitBuilderModeRequestedEvent>());
-        }
-    }
-
-    for (std::size_t i = 0; i < m_buttons.size(); ++i)
-    {
-        const BuildingType type = m_types[i];
-        const std::map<BuildingType, int>::const_iterator it = m_costs.find(type);
-        const int cost = (it != m_costs.end()) ? it->second : 0;
-        m_buttons[i]->setEnabled(buildingBlocks >= cost || m_activeIndex == i);
-    }
-}
-
-void BuildButtonGrid::updateVisibility()
-{
-    // A locked building type's button is hidden until its unlock group is awarded
-    // (REQ-LOCK-BUILDING). Buttons keep their index so hotkeys/affordability stay
-    // stable; they simply appear once the type is unlocked.
-    for (std::size_t i = 0; i < m_buttons.size(); ++i)
-    {
-        m_buttons[i]->setVisible(m_sim->isBuildingUnlocked(m_types[i]));
-    }
-}
-
-void BuildButtonGrid::clearActiveButton()
-{
-    if (m_activeIndex)
-    {
-        m_buttons[*m_activeIndex]->setChecked(false);
-    }
-    m_activeIndex.reset();
-}
-
-void BuildButtonGrid::onBuildButton(int index)
-{
-    if (index < 0 || index >= static_cast<int>(m_buttons.size()))
-    {
-        return;
-    }
-    const std::size_t idx = static_cast<std::size_t>(index);
-
-    if (m_activeIndex == idx)
-    {
-        clearActiveButton();
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<ExitBuilderModeRequestedEvent>());
-        return;
-    }
-
-    if (m_activeIndex)
-    {
-        m_buttons[*m_activeIndex]->setChecked(false);
-    }
-
-    m_activeIndex = idx;
-    m_buttons[idx]->setChecked(true);
-    EventManager::getInstance()->sendEventImmediately(
-        std::make_shared<BuildingTypeSelectedEvent>(m_types[idx]));
-}
-
-void BuildButtonGrid::handleEvent(std::shared_ptr<const BuilderModeExitedEvent> /*event*/)
-{
-    clearActiveButton();
-}
-
-void BuildButtonGrid::handleEvent(std::shared_ptr<const BuildingBlocksChangedEvent> /*event*/)
-{
-    updateAffordability();
-}
-
-void BuildButtonGrid::handleEvent(std::shared_ptr<const UnlockedBuildingsChangedEvent> /*event*/)
-{
-    updateVisibility();
-    updateAffordability();
-}
-
-void BuildButtonGrid::handleEvent(std::shared_ptr<const DeconstructModeChangedEvent> event)
-{
-    m_deconstructButton->setChecked(event->active);
-}
-
-void BuildButtonGrid::handleEvent(std::shared_ptr<const BuildHotkeyPressedEvent> event)
-{
-    for (std::size_t i = 0; i < m_types.size(); ++i)
-    {
-        if (m_types[i] == event->type)
-        {
-            // Equivalent to clicking the build button: a disabled (unaffordable) or
-            // hidden (locked, REQ-LOCK-BUILDING) button cannot be clicked, so the
-            // hotkey is likewise inert.
-            if (m_buttons[i]->isEnabled() && m_buttons[i]->isVisible())
-            {
-                onBuildButton(static_cast<int>(i));
-            }
-            return;
-        }
-    }
-}

src/ui/BuildButtonGrid.h

@@ -1,75 +0,0 @@
-#pragma once
-
-#include <map>
-#include <memory>
-#include <optional>
-#include <string>
-#include <vector>
-
-#include <QWidget>
-
-#include "BuilderModeExitedEvent.h"
-#include "BuildHotkeyPressedEvent.h"
-#include "BuildingBlocksChangedEvent.h"
-#include "BuildingType.h"
-#include "DeconstructModeChangedEvent.h"
-#include "EventHandler.h"
-#include "GameConfig.h"
-#include "UnlockedBuildingsChangedEvent.h"
-
-class QPushButton;
-class Simulation;
-class ItemIconCache;
-
-class BuildButtonGrid : public QWidget,
-                        public CombinedEventHandler<BuilderModeExitedEvent,
-                                                    DeconstructModeChangedEvent,
-                                                    BuildHotkeyPressedEvent,
-                                                    BuildingBlocksChangedEvent,
-                                                    UnlockedBuildingsChangedEvent>
-{
-    Q_OBJECT
-
-public:
-    // iconDir is the directory holding the per-building "<id>.svg" chip icons
-    // (REQ-UI-BUILD-GRID), 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.
-    BuildButtonGrid(Simulation* sim, const GameConfig* config,
-                    const std::string& iconDir, ItemIconCache* itemIcons,
-                    QWidget* parent = nullptr);
-    ~BuildButtonGrid() override;
-
-    void clearActiveButton();
-
-private:
-    // Re-evaluates which build buttons are enabled from the current building block
-    // stock (read from the simulation). If the currently selected tool can no longer
-    // be afforded, it exits builder mode so the button does not stay selected.
-    void updateAffordability();
-
-    // Re-evaluates which build buttons are visible from the current per-building
-    // unlock state (REQ-LOCK-BUILDING); a locked building type's button is hidden.
-    void updateVisibility();
-
-    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;
-    void handleEvent(std::shared_ptr<const BuildingBlocksChangedEvent> event) override;
-    void handleEvent(std::shared_ptr<const UnlockedBuildingsChangedEvent> event) override;
-
-private slots:
-    void onBuildButton(int index);
-
-private:
-    Simulation*                      m_sim;
-    const GameConfig*                m_config;
-    std::string                      m_iconDir;
-    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;
-};

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
@@ -10,21 +12,33 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldPrimitives.h
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldRenderer.h
     ${CMAKE_CURRENT_SOURCE_DIR}/HeaderBar.h
-    ${CMAKE_CURRENT_SOURCE_DIR}/BuildButtonGrid.h
-    ${CMAKE_CURRENT_SOURCE_DIR}/SelectedBuildingPanel.h
-    ${CMAKE_CURRENT_SOURCE_DIR}/FieldSelectionPanel.h
-    ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintPanel.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/FloatingPanel.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/BuildButtonBar.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}/BlueprintLibrary.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSelectionDialog.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipLayoutDialog.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipLayoutPreview.h
     ${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
@@ -35,17 +49,23 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldPrimitives.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldRenderer.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/HeaderBar.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/BuildButtonGrid.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/SelectedBuildingPanel.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/FieldSelectionPanel.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintPanel.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/BuildButtonBar.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
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipLayoutPreview.cpp
     ${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 +1,92 @@
+#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::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 +1,340 @@
+#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 mode are the ones marked, not its label (REQ-UI-CONTROLS-CARD).
+    const bool exitsMode = (action == ControlAction::ExitMode);
+    const std::vector<ControlBinding> bindings = getControlActionBindings(action, context);
+    for (const ControlBinding& binding : bindings)
+    {
+        QLabel* badge = new QLabel(getControlBindingBadge(binding), row);
+        badge->setObjectName(exitsMode ? 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/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"
@@ -58,7 +61,7 @@
 #include "EscapeMenuRequestedEvent.h"
 #include "TracePrintRequestedEvent.h"
 #include "BuildHotkeyPressedEvent.h"
-#include "TemporaryBlueprintRequestedEvent.h"
+#include "GameResetEvent.h"
 #include "BossWaveUpdatedEvent.h"
 #include "BuilderModeExitedEvent.h"
 #include "BlueprintModeExitedEvent.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,
@@ -269,20 +289,6 @@ void GameWorldView::onFrame()
     pruneDespawnedDebris();
     pruneDespawnedActors();
 
-    // Expire copy/paste flashes. Lifetime is wall-clock (the frame delta), so the
-    // flash plays for a fixed real duration regardless of game speed, including
-    // while the game is paused (REQ-BLD-COPY-CONFIG-FEEDBACK).
-    if (!m_copyConfigFlashes.empty())
-    {
-        std::vector<CopyConfigFlash> live;
-        for (CopyConfigFlash flash : m_copyConfigFlashes)
-        {
-            flash.remainingMs -= elapsed;
-            if (flash.remainingMs > 0) { live.push_back(flash); }
-        }
-        m_copyConfigFlashes = std::move(live);
-    }
-
     // Apply held scroll
     {
         const bool viewMoved =
@@ -332,7 +338,7 @@ void GameWorldView::onFrame()
         }
 
         // Unlocked building set changes only after a drop is applied or on Restart
-        // (REQ-LOCK-BUILDING); the build grid rebuilds its visible buttons.
+        // (REQ-LOCK-BUILDING); the build bar rebuilds its visible buttons.
         int newUnlockedBuildingCount = 0;
         for (const BuildingDef& def : m_sim->getConfig().buildings.buildings)
         {
@@ -414,9 +420,8 @@ void GameWorldView::paintGL()
 
 WorldRenderFrame GameWorldView::makeRenderFrame() const
 {
-    return WorldRenderFrame{m_selection, m_buildMode, m_activeBeams, m_copiedConfig,
-                            m_copyConfigFlashes, m_boxSelecting, m_boxStartTile,
-                            m_boxCurrentTile, m_debugDraw};
+    return WorldRenderFrame{m_selection, m_buildMode, m_activeBeams, m_boxSelecting,
+                            m_boxStartTile, m_boxCurrentTile, m_debugDraw};
 }
 
 // ---------------------------------------------------------------------------
@@ -578,16 +583,21 @@ void GameWorldView::placeBlueprintAtTile(QPoint center)
         // Locked building types are excluded from this placement entirely
         // (REQ-LOCK-BUILDING, REQ-LOCK-UI-BLUEPRINT): not validity-checked here.
         if (!m_sim->isBuildingUnlocked(bb.type)) { continue; }
-        if (!canPlaceBuildingHere(bb.type, center + bb.offset, bb.rotation)) { return; }
+        if (resolveBlueprintGhostHere(bb, center).action == BlueprintGhostAction::Invalid)
+        {
+            return;
+        }
     }
 
-    // Cost only applies to buildings that are genuinely new (not rotate-in-place),
-    // and excludes locked building types (REQ-LOCK-UI-BLUEPRINT).
+    // Only genuinely new buildings are charged for: a compatible overlap places nothing
+    // (REQ-UI-BLUEPRINT-OVERLAP) and a transfer changes settings only
+    // (REQ-UI-BLUEPRINT-TRANSFER). Locked building types are excluded from the total
+    // as well (REQ-LOCK-UI-BLUEPRINT).
     int totalCost = 0;
     for (const BlueprintBuilding& bb : bp.buildings)
     {
         if (!m_sim->isBuildingUnlocked(bb.type)) { continue; }
-        if (findRotateInPlaceTarget(m_sim->getFactoryState(), m_sim->getConfig(), bb.type, center + bb.offset, bb.rotation).has_value())
+        if (resolveBlueprintGhostHere(bb, center).action != BlueprintGhostAction::PlaceNew)
         {
             continue;
         }
@@ -600,15 +610,15 @@ void GameWorldView::placeBlueprintAtTile(QPoint center)
     {
         if (!m_sim->isBuildingUnlocked(bb.type)) { continue; }
         const QPoint anchor = center + bb.offset;
-        const std::optional<BuildingId> rotateTarget =
-            findRotateInPlaceTarget(m_sim->getFactoryState(), m_sim->getConfig(), bb.type, anchor, bb.rotation);
-        if (rotateTarget.has_value())
+        const BlueprintGhostResolved resolved = resolveBlueprintGhostHere(bb, center);
+
+        // The building the blueprint wants is already there, facing the same way: leave
+        // it exactly as it is (REQ-UI-BLUEPRINT-OVERLAP).
+        if (resolved.action == BlueprintGhostAction::CompatibleOverlap) { continue; }
+
+        if (resolved.action == BlueprintGhostAction::Transfer)
         {
-            std::shared_ptr<RotateInPlaceCommand> rotateCommand =
-                std::make_shared<RotateInPlaceCommand>();
-            rotateCommand->id          = *rotateTarget;
-            rotateCommand->newRotation = bb.rotation;
-            enqueueCommand(rotateCommand);
+            transferConfigTo(*resolved.targetId, bb);
             continue;
         }
 
@@ -621,26 +631,7 @@ void GameWorldView::placeBlueprintAtTile(QPoint center)
         command->anchor   = anchor;
         command->rotation = bb.rotation;
 
-        if (!bb.recipeId.empty())
-        {
-            if (bb.type == BuildingType::Shipyard)
-            {
-                if (m_sim->isSchematicUnlocked(bb.recipeId))
-                {
-                    command->recipeId = bb.recipeId;
-                }
-            }
-            else
-            {
-                const bool needsUnlockCheck = bb.type == BuildingType::Miner
-                                           || bb.type == BuildingType::Assembler;
-                if (!needsUnlockCheck || m_sim->isRecipeUnlocked(bb.recipeId))
-                {
-                    command->recipeId = bb.recipeId;
-                }
-            }
-        }
-
+        command->recipeId   = unlockedRecipeId(bb);
         command->shipLayout = bb.shipLayout;
 
         if (bb.type == BuildingType::Splitter
@@ -658,6 +649,97 @@ void GameWorldView::placeBlueprintAtTile(QPoint center)
     }
 }
 
+BlueprintGhostResolved GameWorldView::resolveBlueprintGhostHere(const BlueprintBuilding& building,
+                                                               QPoint center) const
+{
+    // A single-building blueprint hit-tests the cursor for its transfer target; a
+    // constellation does not (REQ-UI-BLUEPRINT-TRANSFER). `center` is the cursor tile.
+    // The size is read from the blueprint as stored, before locked types are dropped, so
+    // the gesture behaves the same however much the player has unlocked.
+    const std::optional<QPoint> hoverTile =
+        m_buildMode.getBlueprint().buildings.size() == 1 ? std::make_optional(center)
+                                                         : std::nullopt;
+    return resolveBlueprintGhost(m_sim->getFactoryState(), m_sim->getConfig(),
+                                 building.type, center + building.offset, building.rotation,
+                                 hoverTile);
+}
+
+std::string GameWorldView::unlockedRecipeId(const BlueprintBuilding& building) const
+{
+    // A stored recipe or schematic is applied only while it is unlocked; a locked one
+    // yields no id at all rather than a stale one (REQ-LOCK-UI-BLUEPRINT). Shared by
+    // placement and configuration transfer so the two cannot gate differently.
+    if (building.recipeId.empty()) { return std::string(); }
+
+    if (building.type == BuildingType::Shipyard)
+    {
+        return m_sim->isSchematicUnlocked(building.recipeId) ? building.recipeId
+                                                            : std::string();
+    }
+
+    const bool needsUnlockCheck = building.type == BuildingType::Miner
+                               || building.type == BuildingType::Assembler;
+    if (!needsUnlockCheck || m_sim->isRecipeUnlocked(building.recipeId))
+    {
+        return building.recipeId;
+    }
+    return std::string();
+}
+
+void GameWorldView::transferConfigTo(BuildingId id, const BlueprintBuilding& source)
+{
+    // Hands the blueprint's settings to a building that is already there, changing
+    // nothing else -- no construction site, no cost, no rotation
+    // (REQ-UI-BLUEPRINT-TRANSFER). Every field is sent unconditionally, so a field the
+    // blueprint has nothing stored for clears the target's rather than leaving it: the
+    // target ends up identical to the source. Setting a value the building already holds
+    // is a no-op in the simulation (REQ-MAT-INPUT-BUFFER), which is what keeps clicking
+    // an already-matching building free of buffer and production-progress loss.
+    if (source.type == BuildingType::Splitter)
+    {
+        // Operational splitters are configured by tile, sites by BuildingId (mirrors
+        // 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);
+        if (const Building* building = findBuilding(m_sim->getFactoryState(), id))
+        {
+            std::shared_ptr<SetSplitterFiltersCommand> command =
+                std::make_shared<SetSplitterFiltersCommand>();
+            command->tile    = building->anchor;
+            command->filterA = filterA;
+            command->filterB = filterB;
+            enqueueCommand(command);
+        }
+        else
+        {
+            std::shared_ptr<SetSiteSplitterFiltersCommand> command =
+                std::make_shared<SetSiteSplitterFiltersCommand>();
+            command->id      = id;
+            command->filterA = filterA;
+            command->filterB = filterB;
+            enqueueCommand(command);
+        }
+        return;
+    }
+
+    std::shared_ptr<SetRecipeCommand> recipeCommand = std::make_shared<SetRecipeCommand>();
+    recipeCommand->id       = id;
+    recipeCommand->recipeId = unlockedRecipeId(source);
+    enqueueCommand(recipeCommand);
+
+    // After the schematic, never before: a genuine schematic change resets the layout,
+    // and both commands drain in order at the next tick boundary.
+    if (source.type == BuildingType::Shipyard)
+    {
+        std::shared_ptr<SetShipLayoutCommand> layoutCommand =
+            std::make_shared<SetShipLayoutCommand>();
+        layoutCommand->id     = id;
+        layoutCommand->layout = source.shipLayout.value_or(ShipLayoutConfig{});
+        enqueueCommand(layoutCommand);
+    }
+}
+
 void GameWorldView::updateTunnelGhost()
 {
     // The connection preview and entry/exit switch only apply at a valid placement
@@ -1013,7 +1095,7 @@ 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);
 }
@@ -1025,11 +1107,7 @@ void GameWorldView::keyReleaseEvent(QKeyEvent* event)
         QOpenGLWidget::keyReleaseEvent(event);
         return;
     }
-    if (m_inputMapper.handleKeyRelease(event)) { return; }
-    // Releasing Shift discards the copied building settings (REQ-BLD-COPY-CONFIG).
-    // Stays here rather than moving to the input mapper: Shift is the modifier of a
-    // mouse gesture, not a keyboard action of its own.
-    if (event->key() == Qt::Key_Shift) { m_copiedConfig.reset(); }
+    if (m_inputMapper.handleKeyRelease(event, getControlContext())) { return; }
     QOpenGLWidget::keyReleaseEvent(event);
 }
 
@@ -1043,45 +1121,93 @@ 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();
+    if (m_buildMode.isBuilderMode()) { context.builderType = m_buildMode.getBuilderType(); }
+
+    // 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();
-            }
-            else if (event->modifiers() & Qt::ShiftModifier)
-            {
-                // Shift + right-click copies a building's settings, but only in the
-                // default selection mode (REQ-BLD-COPY-CONFIG).
-                const QPoint tile = coordinates.widgetToTile(event->pos());
-                std::optional<BuildingId> id = buildingAtTile(tile);
-                if (!id.has_value()) { id = siteAtTile(tile); }
-                if (id.has_value()) { copyConfigFrom(*id); }
+                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);
@@ -1090,41 +1216,22 @@ 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
-    {
-        // Shift + left-click applies the copied settings to a same-type building
-        // (REQ-BLD-COPY-CONFIG). Consumes the click so it does not change the
-        // selection. Only active in the default selection mode.
-        if ((event->modifiers() & Qt::ShiftModifier) && m_copiedConfig.has_value())
-        {
-            std::optional<BuildingId> id = buildingAtTile(tile);
-            if (!id.has_value()) { id = siteAtTile(tile); }
-            if (id.has_value())
-            {
-                pasteConfigTo(*id);
-                return;
-            }
-        }
-
-        const bool ctrl = (event->modifiers() & Qt::ControlModifier) != 0;
+        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.
@@ -1132,6 +1239,10 @@ void GameWorldView::mousePressEvent(QMouseEvent* event)
             m_boxStartTile    = tile;
             m_boxCurrentTile  = tile;
         }
+        break;
+
+    default:
+        break;
     }
 }
 
@@ -1146,6 +1257,7 @@ 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;
     }
@@ -1153,6 +1265,7 @@ 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;
     }
@@ -1160,6 +1273,7 @@ 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;
     }
@@ -1180,6 +1294,7 @@ void GameWorldView::selectInBox(bool additive)
         buildingsInBox(m_sim->getFactoryState(), m_boxStartTile, m_boxCurrentTile);
     if (!boxIds.empty())
     {
+        publishSelectionAnchor(mode, boxIds, {}, {});
         m_selection.selectBuildings(boxIds, mode);
         return;
     }
@@ -1190,6 +1305,7 @@ void GameWorldView::selectInBox(bool additive)
         debrisInBox(m_sim->getAdmin(), m_boxStartTile, m_boxCurrentTile);
     if (!boxActors.empty() || !boxDebris.empty())
     {
+        publishSelectionAnchor(mode, {}, boxActors, boxDebris);
         m_selection.selectFieldObjects(boxActors, boxDebris, mode);
         return;
     }
@@ -1198,6 +1314,35 @@ void GameWorldView::selectInBox(bool additive)
     if (!additive) { m_selection.clearAll(); }
 }
 
+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;
+    }
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<SelectionAnchorChangedEvent>(anchorRect));
+}
+
 void GameWorldView::mouseMoveEvent(QMouseEvent* event)
 {
     const WorldCoordinates coordinates = getCoordinates();
@@ -1228,6 +1373,21 @@ 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())
     {
@@ -1259,7 +1419,11 @@ void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
         const std::vector<BuildingId> boxIds =
             buildingsInBox(m_sim->getFactoryState(), m_boxStartTile, m_boxCurrentTile);
 
-        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();
 
@@ -1321,7 +1485,9 @@ 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);
     }
 }
 
@@ -1375,85 +1541,6 @@ void GameWorldView::rotateGhost(bool clockwise)
     }
 }
 
-void GameWorldView::copyConfigFrom(BuildingId id)
-{
-    const std::optional<BuildingConfig> config = readBuildingConfig(*m_sim, id);
-    if (!config.has_value()) { return; }
-
-    // Only cache when there is something to copy: a selected recipe / schematic
-    // (Miner, Assembler, Shipyard) or any Splitter (empty filters = accept-all).
-    // Building types with no settings (Smelter, Reprocessing Plant, Salvage Bay,
-    // belts / tunnels, HQ) leave any existing cache untouched (REQ-BLD-COPY-CONFIG).
-    if (!config->recipeId.has_value() && !config->isSplitter) { return; }
-
-    m_copiedConfig = config;
-    m_copyConfigFlashes.push_back({ id, kCopyFlashDurationMs });
-}
-
-void GameWorldView::pasteConfigTo(BuildingId id)
-{
-    if (!m_copiedConfig.has_value()) { return; }
-
-    const std::optional<BuildingConfig> target = readBuildingConfig(*m_sim, id);
-    if (!target.has_value() || target->type != m_copiedConfig->type) { return; }
-
-    // The paste applies below; flash the target to confirm (REQ-BLD-COPY-CONFIG-FEEDBACK).
-    m_copyConfigFlashes.push_back({ id, kCopyFlashDurationMs });
-
-    const BuildingConfig& source = *m_copiedConfig;
-
-    // The cached settings were valid on a same-type source building, so they are
-    // valid and available on the target: unlock state is global, so a selected
-    // recipe / schematic (REQ-LOCK-UI-RECIPE, REQ-LOCK-UI-SCHEMATIC) and splitter
-    // filter item types (REQ-LOCK-UI-SPLITTER) remain unlocked. Applying reuses the
-    // same configuration commands as the selected building panel, inheriting their
-    // buffer-clearing and mid-cycle-cancel semantics (REQ-MAT-INPUT-BUFFER,
-    // REQ-MAT-OUTPUT-BUFFER, REQ-BLD-SHIPYARD).
-    if (source.isSplitter)
-    {
-        // Operational splitters are configured by tile; sites by BuildingId
-        // (mirrors SelectedBuildingPanel::onSplitterFilterChanged).
-        if (const Building* building = findBuilding(m_sim->getFactoryState(), id))
-        {
-            std::shared_ptr<SetSplitterFiltersCommand> command =
-                std::make_shared<SetSplitterFiltersCommand>();
-            command->tile    = building->anchor;
-            command->filterA = source.splitterFilterA;
-            command->filterB = source.splitterFilterB;
-            enqueueCommand(command);
-        }
-        else
-        {
-            std::shared_ptr<SetSiteSplitterFiltersCommand> command =
-                std::make_shared<SetSiteSplitterFiltersCommand>();
-            command->id      = id;
-            command->filterA = source.splitterFilterA;
-            command->filterB = source.splitterFilterB;
-            enqueueCommand(command);
-        }
-        return;
-    }
-
-    if (source.recipeId.has_value())
-    {
-        std::shared_ptr<SetRecipeCommand> command = std::make_shared<SetRecipeCommand>();
-        command->id       = id;
-        command->recipeId = *source.recipeId;
-        enqueueCommand(command);
-    }
-
-    // For a shipyard the schematic (above) must be applied before its module
-    // layout, so both commands drain in order at the next tick boundary.
-    if (source.type == BuildingType::Shipyard && source.shipLayout.has_value())
-    {
-        std::shared_ptr<SetShipLayoutCommand> command =
-            std::make_shared<SetShipLayoutCommand>();
-        command->id     = id;
-        command->layout = *source.shipLayout;
-        enqueueCommand(command);
-    }
-}
-
 double GameWorldView::getGameSpeed() const
 {
     return m_gameSpeedMultiplier;
@@ -1484,8 +1571,6 @@ void GameWorldView::resetForNewGame()
     m_activeBeams.clear();
     m_schematicChoiceShown = false;
     m_selection.clearAll();
-    m_copiedConfig     = std::nullopt;
-    m_copyConfigFlashes.clear();
     m_boxSelecting     = false;
     m_camera.reset();
     // Drops any key still held across the restart, which also republishes the pan
@@ -1502,6 +1587,10 @@ void GameWorldView::resetForNewGame()
     m_lastArtifactCount = -1;
     EventManager::getInstance()->sendEventImmediately(
         std::make_shared<SelectionChangedEvent>(std::vector<BuildingId>{}));
+    // The one place a restart actually lands (the menu, game over and win dialogs only
+    // enqueue the command), so it is where presentation state belonging to the finished
+    // run is dropped -- e.g. the temporary blueprint (REQ-UI-BLUEPRINT-TEMP).
+    EventManager::getInstance()->sendEventImmediately(std::make_shared<GameResetEvent>());
 	setGameSpeed(1.0);
     // Rebase the wall-clock time source so a fresh run starts from a clean time
     // base. Without this, wall time accumulated while a modal (Game Over, Win, or
@@ -1624,7 +1713,7 @@ 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

@@ -20,7 +20,6 @@
 
 #include "Blueprint.h"
 #include "BuildModeController.h"
-#include "BuildingConfig.h"
 #include "BlueprintModeExitedEvent.h"
 #include "BlueprintPlacementRequestedEvent.h"
 #include "BuilderModeExitedEvent.h"
@@ -65,6 +64,7 @@
 
 struct Command;
 struct ParsedReplay;
+class BlueprintLibrary;
 class ItemIconCache;
 class ReplayPlayer;
 class Simulation;
@@ -103,6 +103,21 @@ 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;
@@ -188,6 +203,16 @@ private:
     std::optional<BuildingId> siteAtTile(QPoint tile) const;
 
     void     placeBlueprintAtTile(QPoint center);
+    // resolveBlueprintGhost (PlacementRules) for one building of the blueprint currently
+    // in placement mode, anchored at the cursor tile `center`.
+    BlueprintGhostResolved resolveBlueprintGhostHere(const BlueprintBuilding& building,
+                                                     QPoint center) const;
+    // The blueprint's stored recipe or schematic id, or empty when it stores none or the
+    // stored one is currently locked (REQ-LOCK-UI-BLUEPRINT).
+    std::string unlockedRecipeId(const BlueprintBuilding& building) const;
+    // Applies a single-building blueprint's settings to the building it is hovering,
+    // instead of placing anything (REQ-UI-BLUEPRINT-TRANSFER).
+    void     transferConfigTo(BuildingId id, const BlueprintBuilding& source);
 
     // Drops despawned or fully-collected debris from the selection
     // (REQ-UI-DEBRIS-CLICK-SELECT). Called each frame from onFrame().
@@ -201,6 +226,15 @@ 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);
+    // 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);
 
@@ -217,12 +251,6 @@ private:
     // Enqueues placements and rotate-in-place commands for the resolved path.
     void                          applyBeltDragPath();
 
-    // Copy-settings gesture (REQ-BLD-COPY-CONFIG): Shift+right-click copies a
-    // building's configuration into m_copiedConfig; Shift+left-click applies it to
-    // another building of the same type via the existing configuration commands.
-    void     copyConfigFrom(BuildingId id);
-    void     pasteConfigTo(BuildingId id);
-
     // Turns the ghost and refreshes everything that depends on its facing: placement
     // validity, the tunnel completion match, and an in-progress belt drag's path.
     // The mode transitions themselves live on m_buildMode.
@@ -271,23 +299,14 @@ private:
     // and to resolve the tunnel ghost sub-tile (REQ-BLD-TUNNEL-MODE).
     QVector2D                            m_cursorWorldPos;
 
-    // Temporary cache for the copy-settings gesture (REQ-BLD-COPY-CONFIG); held
-    // only while Shift is down and cleared on Shift release.
-    std::optional<BuildingConfig> m_copiedConfig;
-
-    // Brief outline flash shown on a building when settings are copied from it or
-    // pasted onto it (REQ-BLD-COPY-CONFIG-FEEDBACK). remainingMs counts down in
-    // wall-clock time so the flash plays at a fixed length regardless of game speed
-    // (and while paused).
-    std::vector<CopyConfigFlash> m_copyConfigFlashes;
-    static constexpr qint64      kCopyFlashDurationMs = 300;
-
     bool     m_debugDraw;
 
     // Owns the selection across all three categories and the rules for moving
     // 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;

src/ui/HeaderBar.cpp

@@ -3,7 +3,6 @@
 #include <cmath>
 #include <string>
 
-#include <QFontMetrics>
 #include <QHBoxLayout>
 #include <QIcon>
 #include <QLabel>
@@ -21,13 +20,6 @@
 #include "SpeedChangeRequestedEvent.h"
 #include "Tick.h"
 
-namespace
-{
-    // Item id of the building blocks resource, whose icon stands in for the "Blocks"
-    // word in the header stock and expand button (REQ-UI-BLOCKS-ICON).
-    const char* const kBlockItemId = "building_block";
-}
-
 const double HeaderBar::kSpeeds[]   = { 0.0, 0.5, 1.0, 2.0, 10.0 };
 const int    HeaderBar::kSpeedCount = 5;
 
@@ -127,19 +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).
@@ -158,7 +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.cpp

@@ -46,3 +46,11 @@ QPixmap renderCaptionWithIcon(const QString& text, const QPixmap& icon,
 
     return pixmap;
 }
+
+QSize getLogicalSize(const QPixmap& pixmap)
+{
+    if (pixmap.isNull()) { return QSize(0, 0); }
+    const qreal dpr = pixmap.devicePixelRatio();
+    return QSize(static_cast<int>(pixmap.width()  / dpr),
+                 static_cast<int>(pixmap.height() / dpr));
+}

src/ui/IconCaption.h

@@ -3,6 +3,7 @@
 #include <QColor>
 #include <QFont>
 #include <QPixmap>
+#include <QSize>
 #include <QString>
 
 // Renders `text` followed by `icon` to its right, vertically centered, onto a
@@ -14,3 +15,17 @@
 // theme-correct; the result is devicePixelRatio-aware so text and icon stay crisp.
 QPixmap renderCaptionWithIcon(const QString& text, const QPixmap& icon,
                               const QFont& font, const QColor& textColor);
+
+// A pixmap's size in device-independent pixels. The pixmaps composed by
+// renderCaptionWithIcon and its callers are rasterized at the device pixel ratio, so
+// their raw size is not the size to lay them out at.
+QSize getLogicalSize(const QPixmap& pixmap);
+
+// 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

@@ -5,8 +5,11 @@
 
 #include <QKeyEvent>
 
+#include "BlueprintSaveRequestedEvent.h"
+#include "BlueprintSelectionRequestedEvent.h"
 #include "BuildHotkeyPressedEvent.h"
 #include "BuildingType.h"
+#include "ControlAction.h"
 #include "DebugDrawToggleRequestedEvent.h"
 #include "EscapeMenuRequestedEvent.h"
 #include "EventManager.h"
@@ -15,7 +18,8 @@
 #include "PanDirectionChangedEvent.h"
 #include "PauseToggleRequestedEvent.h"
 #include "SpeedStepRequestedEvent.h"
-#include "TemporaryBlueprintRequestedEvent.h"
+#include "TemporaryBlueprintCaptureRequestedEvent.h"
+#include "TemporaryBlueprintPlaceRequestedEvent.h"
 #include "TracePrintRequestedEvent.h"
 
 namespace
@@ -51,7 +55,30 @@ std::optional<BuildingType> buildHotkeyType(int digit, bool shiftHeld)
 
 }  // namespace
 
-bool InputMapper::handleKeyPress(QKeyEvent* event)
+QString InputMapper::getBuildHotkeyLabel(BuildingType type)
+{
+    // Searched out of the binding table above rather than spelled out a second time,
+    // so a badge can never claim a key the handler does not act on. The shift glyph
+    // is written as a code point because the sources are not guaranteed to be read
+    // as UTF-8 by every compiler this builds with. A plain stroke arrow rather than
+    // U+21E7 UPWARDS WHITE ARROW: the standard UI fonts do not all carry the outlined
+    // shift glyph, and the substitute they fall back to is unreadable at badge size.
+    const QChar shiftGlyph(0x2191);  // U+2191 UPWARDS ARROW
+    for (int digit = 1; digit <= 9; ++digit)
+    {
+        if (buildHotkeyType(digit, false) == type)
+        {
+            return QString::number(digit);
+        }
+        if (buildHotkeyType(digit, true) == type)
+        {
+            return shiftGlyph + QString::number(digit);
+        }
+    }
+    return QString();
+}
+
+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.
@@ -60,6 +87,9 @@ 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)
     {
@@ -74,79 +104,102 @@ bool InputMapper::handleKeyPress(QKeyEvent* event)
         }
     }
 
+    // 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_T:
-        // Request a temporary blueprint from the current selection (REQ-UI-BLUEPRINT-TEMP).
-        // The BlueprintPanel 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<TemporaryBlueprintRequestedEvent>());
-        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::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

@@ -1,13 +1,21 @@
 #pragma once
 
+#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:
 //
@@ -24,10 +32,17 @@ class QKeyEvent;
 class InputMapper
 {
 public:
+    // The build hotkey that selects the given building type, spelled for display on
+    // its build button's badge (REQ-UI-BUILD-COST): "1" for a plain digit, "⇧1" for
+    // a Shift+digit, and an empty string for a building type with no build hotkey.
+    // Lives here so the badge and the key handling read the same binding table.
+    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 +1,60 @@
+#include "ItemProducers.h"
+
+#include "GameConfig.h"
+#include "RecipesConfig.h"
+#include "Simulation.h"
+
+namespace
+{
+
+bool producesItem(const RecipeDef& recipe, const std::string& itemId)
+{
+    for (const RecipeOutput& output : recipe.outputs)
+    {
+        if (output.item == itemId)
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
+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

@@ -7,15 +7,19 @@
 
 #include <QApplication>
 #include <QCloseEvent>
+#include <QDialog>
 #include <QDir>
 #include <QFile>
+#include <QInputDialog>
+#include <QLineEdit>
 #include <QMessageBox>
 #include <QPushButton>
 #include <QResizeEvent>
 #include <QVBoxLayout>
 
-#include "BlueprintPanel.h"
-#include "BuildButtonGrid.h"
+#include "BlueprintLibrary.h"
+#include "BlueprintSelectionDialog.h"
+#include "BuildButtonBar.h"
 #include "BuildingSystem.h"
 #include "Command.h"
 #include "CommandRequestedEvent.h"
@@ -25,9 +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"
@@ -45,50 +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);
 
-    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 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(),
+                                          m_buildingIcons.get(), m_itemIcons.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();
+    // 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_selectedBuildingPanel = new SelectedBuildingPanel(sim, &sim->getConfig(), m_sidePanel);
-    m_buildButtonGrid       = new BuildButtonGrid(sim, &sim->getConfig(), iconDir, m_itemIcons.get(), m_sidePanel);
-    m_blueprintPanel        = new BlueprintPanel(sim, &sim->getConfig(), m_sidePanel);
+    // 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);
 
-    sideLayout->addWidget(m_selectedBuildingPanel, 1);
-    sideLayout->addWidget(m_buildButtonGrid,       1);
-    sideLayout->addWidget(m_blueprintPanel,        1);
-
-    // Draw a thin border around each of the three side-panel sections. The class
-    // scoped selectors keep the border on the panels themselves rather than
-    // cascading onto their child widgets; WA_StyledBackground lets the plain
-    // QWidget subclasses honor the stylesheet box (border/background).
-    for (QWidget* panel : { static_cast<QWidget*>(m_selectedBuildingPanel),
-                            static_cast<QWidget*>(m_buildButtonGrid),
-                            static_cast<QWidget*>(m_blueprintPanel) })
-    {
-        panel->setAttribute(Qt::WA_StyledBackground, true);
-    }
-    m_sidePanel->setStyleSheet(QStringLiteral(
-        "SelectedBuildingPanel, BuildButtonGrid, BlueprintPanel {"
-        " 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).
@@ -158,13 +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);
+    // 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)
@@ -172,7 +224,8 @@ 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();
 
     std::shared_ptr<ApplySchematicChoiceCommand> command =
@@ -232,6 +285,9 @@ 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)
@@ -262,7 +318,10 @@ 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 =
@@ -274,6 +333,45 @@ 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
@@ -330,7 +428,9 @@ 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>();
@@ -359,6 +459,47 @@ void MainWindow::handleEvent(std::shared_ptr<const RecipeSelectionRequestedEvent
     }
 }
 
+void MainWindow::handleEvent(std::shared_ptr<const BlueprintSaveRequestedEvent> /*event*/)
+{
+    // Ctrl+C has effect only when something player-placeable is selected; otherwise no
+    // dialog opens at all (REQ-UI-BLUEPRINT-CREATE).
+    if (!m_blueprintLibrary->getCanCaptureSelection()) { return; }
+
+    // Both scopes are held across the naming dialog and the selection dialog it hands
+    // over to, so the dim never blinks off and the simulation is not resumed in between
+    // (REQ-UI-MODAL-DIM).
+    ModalPauseScope pause(*m_gameWorldView);
+    ModalDimScope   dim(*m_dimOverlay);
+
+    bool ok = false;
+    const QString name = QInputDialog::getText(
+        this, tr("Create Blueprint"), tr("Blueprint name:"), QLineEdit::Normal,
+        QString(), &ok);
+    // Cancel, Escape, or an empty name: no blueprint, and no selection dialog.
+    if (!ok || name.trimmed().isEmpty()) { return; }
+
+    m_blueprintLibrary->saveSelectionAs(name.trimmed());
+    showBlueprintSelectionDialog();
+}
+
+void MainWindow::handleEvent(std::shared_ptr<const BlueprintSelectionRequestedEvent> /*event*/)
+{
+    ModalPauseScope pause(*m_gameWorldView);
+    ModalDimScope   dim(*m_dimOverlay);
+    showBlueprintSelectionDialog();
+}
+
+void MainWindow::showBlueprintSelectionDialog()
+{
+    BlueprintSelectionDialog dialog(m_blueprintLibrary.get(), m_itemIcons.get(), this);
+    if (dialog.exec() == QDialog::Accepted && dialog.getChosenIndex().has_value())
+    {
+        // Entered after the dialog has closed, which is the order REQ-UI-BLUEPRINT-CARD
+        // describes: clicking a card closes the dialog and enters placement mode.
+        m_blueprintLibrary->beginPlacement(*dialog.getChosenIndex());
+    }
+}
+
 void MainWindow::handleEvent(std::shared_ptr<const GameOverEvent> /*event*/)
 {
     const Tick tick = m_sim->getCurrentTick();

src/ui/MainWindow.h

@@ -7,9 +7,12 @@
 
 #include <QWidget>
 
+#include "BlueprintSaveRequestedEvent.h"
+#include "BlueprintSelectionRequestedEvent.h"
 #include "BuildingId.h"
 #include "EscapeMenuRequestedEvent.h"
 #include "EventHandler.h"
+#include "FloatingLayoutInvalidatedEvent.h"
 #include "GameConfig.h"
 #include "GameOverEvent.h"
 #include "LayoutDialogRequestedEvent.h"
@@ -26,11 +29,14 @@ struct ParsedReplay;
 class Simulation;
 class GameWorldView;
 class HeaderBar;
-class SelectedBuildingPanel;
-class BuildButtonGrid;
-class BlueprintPanel;
+class SelectionPanel;
+class ControlsPanel;
+class BuildButtonBar;
+class BlueprintLibrary;
+class BuildingIconCache;
 class ItemIconCache;
 class QCloseEvent;
+class QDialog;
 class QResizeEvent;
 
 class MainWindow : public QWidget,
@@ -39,7 +45,10 @@ class MainWindow : public QWidget,
                                                WinEvent,
                                                EscapeMenuRequestedEvent,
                                                LayoutDialogRequestedEvent,
-                                               RecipeSelectionRequestedEvent>
+                                               RecipeSelectionRequestedEvent,
+                                               BlueprintSaveRequestedEvent,
+                                               BlueprintSelectionRequestedEvent,
+                                               FloatingLayoutInvalidatedEvent>
 {
     Q_OBJECT
 
@@ -59,6 +68,9 @@ private:
     void handleEvent(std::shared_ptr<const EscapeMenuRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const LayoutDialogRequestedEvent> event) override;
     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
@@ -71,6 +83,19 @@ private:
     void openShipLayoutDialog(BuildingId shipyardId,
                               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:
@@ -78,16 +103,25 @@ private:
     VisualsConfig          m_visuals;
     Simulation*            m_sim;
     // One per-item icon cache for the whole window (REQ-UI-ITEM-ICON): the header,
-    // build grid, world view, and recipe dialog all rasterize the same SVGs.
+    // 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;
-    BuildButtonGrid*       m_buildButtonGrid;
-    BlueprintPanel*        m_blueprintPanel;
-    QWidget*               m_sidePanel;
+    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;
     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 +1,196 @@
+#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
+
+
+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.outputs.empty())
+    {
+        const QChar rightArrow(0x2192);  // U+2192 RIGHTWARDS ARROW
+        addAndShow(m_amountsLayout, new QLabel(QString(rightArrow), m_amountsRow));
+    }
+    addAmounts(spec.outputs);
+
+    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 +1,115 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <vector>
+
+#include <QString>
+#include <QWidget>
+
+#include "BuildingType.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;
+        // 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<Amount>         outputs;
+        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 && outputs == other.outputs
+                && durationSeconds == other.durationSeconds
+                && durationIsAddition == other.durationIsAddition;
+        }
+
+        bool isEmpty() const { return inputs.empty() && outputs.empty(); }
+    };
+
+    // 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

@@ -2,60 +2,46 @@
 
 #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 "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)
+std::vector<RecipeLineRow::Amount> toAmounts(const std::vector<RecipeOutput>& outputs)
 {
-    const QString name = QString::fromStdString(toDisplayName(def.id));
-
-    QStringList lines;
-    lines << QObject::tr("Ship: %1").arg(name);
-
-    if (def.schematic.materials.empty())
+    std::vector<RecipeLineRow::Amount> amounts;
+    amounts.reserve(outputs.size());
+    for (const RecipeOutput& output : outputs)
     {
-        lines << QObject::tr("Materials: none");
+        amounts.push_back(RecipeLineRow::Amount{ output.item, output.amount });
     }
-    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');
+    return amounts;
 }
 
 }  // namespace
@@ -64,16 +50,30 @@ 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 +87,15 @@ 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.outputs         = toAmounts(recipe.outputs);
+            line.durationSeconds = recipe.durationSeconds;
+
             options.push_back({recipe.id,
                                QString::fromStdString(toDisplayName(recipe.id)),
-                               buildRecipeTooltip(recipe),
-                               iconItemId});
+                               line});
         }
     }
 
@@ -105,46 +104,77 @@ 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 +183,9 @@ RecipeSelectionDialog::RecipeSelectionDialog(
             onOptionClicked(index);
         });
     }
+    listLayout->addStretch(1);
+
+    scrollArea->setWidget(list);
 }
 
 std::optional<std::string> RecipeSelectionDialog::getChosenId() const

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.
@@ -20,23 +22,23 @@ 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.
 class RecipeSelectionDialog : public QDialog
@@ -44,12 +46,10 @@ 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;
 

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 +6,35 @@
 #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;
+}
+
+std::vector<RecipeLineRow::Amount> toAmounts(const std::vector<RecipeOutput>& outputs)
+{
+    std::vector<RecipeLineRow::Amount> amounts;
+    amounts.reserve(outputs.size());
+    for (const RecipeOutput& output : outputs)
+    {
+        amounts.push_back(RecipeLineRow::Amount{ output.item, output.amount });
+    }
+    return amounts;
+}
+
 QString grantKindLabel(SchematicType type)
 {
     switch (type)
@@ -28,7 +51,8 @@ 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 +80,12 @@ 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 +137,24 @@ 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.outputs         = toAmounts(def->outputs);
+                    spec.durationSeconds = def->durationSeconds;
+
+                    RecipeLineRow* line =
+                        new RecipeLineRow(itemIcons, buildingIcons, card);
+                    line->setCardChrome(true);
+                    cardLayout->addWidget(line);
+                    line->setLine(spec);
                 }
             }
         }