Rename Demolish to Deconstruct; add build button grid icons

Rename the Demolish* terminology to Deconstruct* across the simulation,
events, UI, tests, and docs (DemolishCommand and the DemolishMode* events
become their Deconstruct* equivalents), aligning with the deconstruction
queue at HEAD.

Add per-building SVG icons for the build button grid (REQ-UI-BUILD-GRID):
one color-chip icon per placeable building under data/icons/buildings,
loaded from disk at runtime and rendered with QtSvg onto each build button.
An unaffordable building's button shows a grey-recolored variant via a
QIcon Disabled-mode pixmap (REQ-UI-BUILD-DISABLED). Adds the Qt5::Svg
dependency and deploys Qt5Svg.dll.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y7N59FsLA5e2kuVdqe4Uhc

CMakeLists.txt

@@ -24,7 +24,7 @@ set(CMAKE_BUILD_TYPE_INIT "Release")
 
 # Qt ---------------------------------------------------------------------------
 
-find_package(Qt5 COMPONENTS Widgets Network Multimedia Charts REQUIRED)
+find_package(Qt5 COMPONENTS Widgets Network Multimedia Charts Svg REQUIRED)
 
 if(Qt5Widgets_FOUND)
 	message(STATUS "Found Qt ${Qt5Widgets_VERSION_STRING}")
@@ -64,6 +64,7 @@ function(COPY_QT_BINARIES TARGET_DIR IS_DEBUG)
 	configure_file("${QT_BINARY_DIR}/Qt5Network${SUFFIX}.dll" "${TARGET_DIR}/Qt5Network${SUFFIX}.dll" COPYONLY)
 	configure_file("${QT_BINARY_DIR}/Qt5Widgets${SUFFIX}.dll" "${TARGET_DIR}/Qt5Widgets${SUFFIX}.dll" COPYONLY)
 	configure_file("${QT_BINARY_DIR}/Qt5Multimedia${SUFFIX}.dll" "${TARGET_DIR}/Qt5Multimedia${SUFFIX}.dll" COPYONLY)
+	configure_file("${QT_BINARY_DIR}/Qt5Svg${SUFFIX}.dll" "${TARGET_DIR}/Qt5Svg${SUFFIX}.dll" COPYONLY)
 endfunction(COPY_QT_BINARIES)
 
 

bin/app/data/config/modules.toml

@@ -7,10 +7,9 @@
 # Combat stats are placeholders until the arena balancing pass;
 # production_time_seconds values come from the numbers pass.
 #
-# Unlock progression is mostly disabled (unlock_at_station_level = -1) pending
-# the pacing pass. The railguns are the exception: railgun_m is gated to
-# station level 1, and railgun_l requires railgun_m to be unlocked first
-# (unlock_requires) — a demonstration of the prerequisite chain.
+# Unlock gating is defined in unlocks.toml, not here (REQ-LOCK-EXPLICIT): a
+# module id granted by an unlock group starts locked and is awarded via a
+# defence station drop; ids absent from unlocks.toml (railgun_s) start unlocked.
 #
 # Surface mask footprint ladder — footprints gate which hulls can mount a
 # module, purely through geometry (see ships.toml for the matching hull
@@ -33,7 +32,6 @@
 [[module]]
 id = "railgun_s"
 tooltip = "Small railgun. Fast-firing, short range, low damage; fits any hull."
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "railgun_s_module", amount = 1}]
 production_time_seconds = 1
@@ -49,7 +47,6 @@ attack_rate_hz = 2.0
 [[module]]
 id = "railgun_m"
 tooltip = "Medium railgun. Higher damage at longer range; needs a 2x2 slot."
-unlock_at_station_level = 2
 surface_mask = [
     "OO",
     "OO"]
@@ -67,8 +64,6 @@ attack_rate_hz = 1.5
 [[module]]
 id = "railgun_l"
 tooltip = "Large railgun. Heavy damage at long range; needs a 3x3 slot."
-unlock_at_station_level = 6
-unlock_requires = ["railgun_m"]
 surface_mask = [
     "OOO",
     "OOO",
@@ -90,7 +85,6 @@ attack_rate_hz = 0.8
 [[module]]
 id = "salvager"
 tooltip = "Collects scrap from wrecks and stores it in the ship's cargo hold."
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "salvager_module", amount = 1}]
 production_time_seconds = 1
@@ -106,7 +100,6 @@ collection_rate_hz = 0.5
 [[module]]
 id = "repair_tool"
 tooltip = "Repairs damaged friendly ships and defence stations within range."
-unlock_at_station_level = 0
 surface_mask = ["O"]
 materials = [{item = "repair_tool_module", amount = 1}]
 production_time_seconds = 1
@@ -125,7 +118,6 @@ repair_range_m = 80
 [[module]]
 id = "afterburner"
 tooltip = "Greatly boosts top speed and forward acceleration."
-unlock_at_station_level = 2
 surface_mask = ["OOO"]
 materials = [{item = "afterburner_module", amount = 1}]
 production_time_seconds = 1
@@ -140,7 +132,6 @@ added_main_acceleration_mpss = 60
 [[module]]
 id = "maneuvering_thrusters"
 tooltip = "Improves top speed and lateral/braking acceleration."
-unlock_at_station_level = 1
 surface_mask = ["OO"]
 materials = [{item = "maneuvering_thrusters_module", amount = 1}]
 production_time_seconds = 1
@@ -158,7 +149,6 @@ added_maneuvering_acceleration_mpss = 10
 [[module]]
 id = "armor_plates"
 tooltip = "Adds a large flat bonus to the ship's hit points."
-unlock_at_station_level = 0
 surface_mask = ["OO"]
 materials = [{item = "armor_plates_module", amount = 1}]
 production_time_seconds = 1
@@ -172,7 +162,6 @@ added_hp = 1200
 [[module]]
 id = "sensor_booster"
 tooltip = "Extends the ship's sensor range."
-unlock_at_station_level = 1
 surface_mask = ["OO"]
 materials = [{item = "sensor_booster_module", amount = 1}]
 production_time_seconds = 1
@@ -189,7 +178,6 @@ added_sensor_range_m = 50
 [[module]]
 id = "weapon_upgrade"
 tooltip = "Increases the damage of all weapons on the ship."
-unlock_at_station_level = 4
 surface_mask = [
     "OO",
     "OX",
@@ -206,7 +194,6 @@ multiplied_damage = 1.2
 [[module]]
 id = "weapon_primer"
 tooltip = "Increases the fire rate of all weapons on the ship."
-unlock_at_station_level = 4
 surface_mask = [
     "OO",
     "OX",
@@ -223,7 +210,6 @@ multiplied_attack_rate_hz = 1.2
 [[module]]
 id = "weapon_stabilizer"
 tooltip = "Extends weapon range at the cost of some fire rate."
-unlock_at_station_level = 3
 surface_mask = [
     "OO",
     "OX",
@@ -247,7 +233,6 @@ multiplied_attack_rate_hz = 0.8
 [[module]]
 id = "drone_bay"
 tooltip = "Drone launch bay (capability not yet implemented)."
-unlock_at_station_level = 5
 surface_mask = [
     "OO",
     "OO"]
@@ -260,7 +245,6 @@ glyph = "Db"
 [[module]]
 id = "drone_hangar"
 tooltip = "Large drone hangar (capability not yet implemented)."
-unlock_at_station_level = 9
 surface_mask = [
     "OOOOOO",
     "OOOOOO"]

bin/app/data/config/recipes.toml

@@ -142,12 +142,12 @@ duration_seconds = 1.5
 
 # Depth-3 chain (ore -> ingot -> plate -> block) is the factory's
 # doubling-time knob; see the block economy rules in docs/balancing/rules.md.
-# Explicitly unlocked at start (-1): building blocks appear in no
-# schematic's materials, so implicit unlocking can never reach this recipe.
+# 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"
-unlock_at_station_level = -1
 building = "assembler"
+unlocked_at_start = true
 inputs = [{item = "steel_plate", amount = 2}]
 outputs = [{item = "building_block", amount = 4}]
 duration_seconds = 2.0
@@ -220,15 +220,14 @@ outputs = [{item = "capital_core", amount = 1}]
 duration_seconds = 10.0
 
 # -----------------------------------------------------------------------------
-# Shortcut recipes — drop-only assembler recipe schematics
-# (unlock_at_station_level >= 0). Pure rewards: item threat stays defined by
+# 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.
 # -----------------------------------------------------------------------------
 
 [[recipe]]
 id = "shortcut_steel_plate"
-unlock_at_station_level = 1
 building = "assembler"
 inputs = [{item = "iron_ore", amount = 3}]
 outputs = [{item = "steel_plate", amount = 1}]
@@ -236,7 +235,6 @@ duration_seconds = 2.0
 
 [[recipe]]
 id = "shortcut_control_chip"
-unlock_at_station_level = 2
 building = "assembler"
 inputs = [{item = "quartz", amount = 2}]
 outputs = [{item = "control_chip", amount = 1}]
@@ -244,7 +242,6 @@ duration_seconds = 4.0
 
 [[recipe]]
 id = "shortcut_hardened_steel"
-unlock_at_station_level = 2
 building = "assembler"
 inputs = [{item = "iron_ingot", amount = 4}]
 outputs = [{item = "hardened_steel", amount = 1}]

bin/app/data/config/ships.toml

@@ -4,10 +4,9 @@
 # content; stats, materials, and production times are placeholders until the
 # recipe and balancing passes.
 #
-# Unlock progression is mostly disabled (unlock_at_station_level = -1) pending
-# the balancing pass. The capital hulls are the exception: battleship is gated
-# to station level 1, and dreadnought (level 2) requires battleship to be
-# unlocked first (unlock_requires) — a demonstration of the prerequisite chain.
+# Unlock gating is defined in unlocks.toml, not here (REQ-LOCK-EXPLICIT): a ship
+# id granted by an unlock group starts locked and is awarded via a defence
+# station drop; ids absent from unlocks.toml (drone, frigate) start unlocked.
 #
 # Size classes:
 #   xs  drone                      1 cell — exactly one 1x1 module
@@ -22,7 +21,6 @@
 
 [[ship]]
 id = "drone"
-unlock_at_station_level = -1
 layout = ["O"]
 default_modules = [{type = "railgun_s", x = 0, y = 0, rotation = "east"}]
 
@@ -49,7 +47,6 @@ sensor_range_m = 150
 # L-shaped weapon modifier, or an afterburner spanning the full center line.
 [[ship]]
 id = "frigate"
-unlock_at_station_level = -1
 layout = [
     "XOX",
     "OOO",
@@ -84,7 +81,6 @@ sensor_range_m = 200
 # mount medium hardware.
 [[ship]]
 id = "destroyer"
-unlock_at_station_level = 0
 layout = [
     "OXOXO",
     "OOOOO",
@@ -120,7 +116,6 @@ sensor_range_m = 220
 # supports; no 3x3 area exists for an l gun.
 [[ship]]
 id = "cruiser"
-unlock_at_station_level = 2
 layout = [
     "XOOX",
     "OOOO",
@@ -158,8 +153,6 @@ sensor_range_m = 250
 # stern leave no 3x3 area for an l gun and no 2x6 area for a drone hangar.
 [[ship]]
 id = "battlecruiser"
-unlock_at_station_level = 4
-unlock_requires = ["cruiser"]
 layout = [
     "OOXXOO",
     "OOOOOO",
@@ -201,8 +194,6 @@ sensor_range_m = 260
 # so no 2x6 drone hangar fits.
 [[ship]]
 id = "battleship"
-unlock_at_station_level = 6
-unlock_requires = ["battlecruiser"]
 layout = [
     "XOOOOX",
     "OOOOOO",
@@ -244,8 +235,6 @@ sensor_range_m = 280
 # stay the only hangar hull. Bow and stern strips hold supports.
 [[ship]]
 id = "dreadnought"
-unlock_at_station_level = 8
-unlock_requires = ["battleship"]
 layout = [
     "XXXOOOOOXXX",
     "OOOXOOOXOOO",
@@ -288,8 +277,6 @@ sensor_range_m = 300
 # the lower decks hold supports and 2x2 point-defense m guns.
 [[ship]]
 id = "carrier"
-unlock_at_station_level = 9
-unlock_requires = ["battleship"]
 layout = [
     "XOOOOOOOOX",
     "OOOOOOOOOO",

bin/app/data/config/unlocks.toml

@@ -0,0 +1,140 @@
+# Unlock groups (REQ-LOCK-EXPLICIT, REQ-DEF-SCHEMATIC-DROP).
+#
+# Each [[unlock]] is a group of ships/modules/buildings/recipes awarded together
+# from a single defence station drop. Anything NOT granted by any group is
+# available from game start. `station_level` gates when a group becomes eligible;
+# `requires` lists prerequisite unlock-group ids (REQ-LOCK-PREREQ).
+#
+# Most entries below are single-item groups that reproduce the previous per-item
+# progression. The salvage_operations and reprocessing groups are the grouped
+# unlocks: they lock the salvager module + salvage bay, and the reprocessing
+# plant, from game start.
+
+# --- Grouped unlocks -------------------------------------------------------
+
+[[unlock]]
+id = "salvage_operations"
+station_level = 1
+modules = ["salvager"]
+buildings = ["salvage_bay"]
+
+[[unlock]]
+id = "reprocessing"
+station_level = 2
+buildings = ["reprocessing_plant"]
+
+# --- Ships -----------------------------------------------------------------
+
+[[unlock]]
+id = "destroyer"
+station_level = 0
+ships = ["destroyer"]
+
+[[unlock]]
+id = "cruiser"
+station_level = 2
+ships = ["cruiser"]
+
+[[unlock]]
+id = "battlecruiser"
+station_level = 4
+requires = ["cruiser"]
+ships = ["battlecruiser"]
+
+[[unlock]]
+id = "battleship"
+station_level = 6
+requires = ["battlecruiser"]
+ships = ["battleship"]
+
+[[unlock]]
+id = "dreadnought"
+station_level = 8
+requires = ["battleship"]
+ships = ["dreadnought"]
+
+[[unlock]]
+id = "carrier"
+station_level = 9
+requires = ["battleship"]
+ships = ["carrier"]
+
+# --- Modules ---------------------------------------------------------------
+
+[[unlock]]
+id = "repair_tool"
+station_level = 0
+modules = ["repair_tool"]
+
+[[unlock]]
+id = "armor_plates"
+station_level = 0
+modules = ["armor_plates"]
+
+[[unlock]]
+id = "maneuvering_thrusters"
+station_level = 1
+modules = ["maneuvering_thrusters"]
+
+[[unlock]]
+id = "sensor_booster"
+station_level = 1
+modules = ["sensor_booster"]
+
+[[unlock]]
+id = "railgun_m"
+station_level = 2
+modules = ["railgun_m"]
+
+[[unlock]]
+id = "afterburner"
+station_level = 2
+modules = ["afterburner"]
+
+[[unlock]]
+id = "weapon_stabilizer"
+station_level = 3
+modules = ["weapon_stabilizer"]
+
+[[unlock]]
+id = "weapon_upgrade"
+station_level = 4
+modules = ["weapon_upgrade"]
+
+[[unlock]]
+id = "weapon_primer"
+station_level = 4
+modules = ["weapon_primer"]
+
+[[unlock]]
+id = "drone_bay"
+station_level = 5
+modules = ["drone_bay"]
+
+[[unlock]]
+id = "railgun_l"
+station_level = 6
+requires = ["railgun_m"]
+modules = ["railgun_l"]
+
+[[unlock]]
+id = "drone_hangar"
+station_level = 9
+modules = ["drone_hangar"]
+
+# --- Assembler recipes -----------------------------------------------------
+
+[[unlock]]
+id = "shortcut_steel_plate"
+station_level = 1
+recipes = ["shortcut_steel_plate"]
+
+[[unlock]]
+id = "shortcut_control_chip"
+station_level = 2
+recipes = ["shortcut_control_chip"]
+
+[[unlock]]
+id = "shortcut_hardened_steel"
+station_level = 2
+recipes = ["shortcut_hardened_steel"]

bin/app/data/config/visuals.toml

@@ -335,7 +335,7 @@ salvage_color = "#33ccff"
 width_px      = 2
 
 # -----------------------------------------------------------------------------
-# Build / demolish / selection overlays
+# Build / deconstruct / selection overlays
 #
 # All overlay colors carry an alpha channel so they composite over the
 # underlying scene.
@@ -344,7 +344,7 @@ width_px      = 2
 [overlays]
 ghost_valid    = "#ffffff44"   # builder-mode ghost, placement allowed (REQ-BLD-GHOST)
 ghost_invalid  = "#ff000044"   # builder-mode ghost, placement invalid (REQ-BLD-PLACE-VALID)
-demolish_tint  = "#ff000033"   # demolish-mode hover tint
+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)

bin/app/data/config/world.toml

@@ -1,6 +1,7 @@
 [world]
 height_tiles = 40
 refund_percentage = 100
+deconstruction_time_seconds = 0.1
 starting_building_blocks = 200
 scrap_despawn_seconds = 120
 scrap_per_threat = 0.25

bin/app/data/icons/buildings/assembler.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#3a6fa8"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <circle cx="16" cy="16" r="6.2"/><circle cx="16" cy="16" r="2.2"/><path d="M16 5.5v3M16 23.5v3M5.5 16h3M23.5 16h3M8.6 8.6 10.7 10.7M23.4 8.6 21.3 10.7M8.6 23.4 10.7 21.3M23.4 23.4 21.3 21.3"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/belt.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#6a6a6a"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <rect x="4" y="10" width="24" height="12" rx="3"/><path d="M9 13 12.5 16 9 19"/><path d="M14.5 13 18 16 14.5 19"/><path d="M20 13 23.5 16 20 19"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/deconstruct.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#cc3333"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M7 10h18"/><path d="M9.5 10 11 26h10l1.5-16"/><path d="M13 10V6.5h6V10"/><path d="M13.5 14v8M18.5 14v8"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/miner.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#6b4a2c"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <rect x="9" y="5" width="14" height="8" rx="1.5"/><path d="M11 13 16 26 21 13"/><path d="M13 17.5h6"/><path d="M14.5 21.5h3"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/reprocessing_plant.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#6a3a8a"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <circle cx="12" cy="18" r="4"/><circle cx="20" cy="18" r="4"/><path d="M10.6 16.6 13.4 19.4M13.4 16.6 10.6 19.4M18.6 16.6 21.4 19.4M21.4 16.6 18.6 19.4"/><path d="M16 4v8"/><path d="M13 9 16 12 19 9"/><path d="M16 24v4"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/salvage_bay.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#b8a23a"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M7 13h18l-2 13H9z"/><path d="M16 3v7"/><path d="M12 7 16 11 20 7"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/shipyard.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#3f6580"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M16 4c2 3 2.6 6 2.6 9.5V16h-5.2v-2.5C13.4 10 14 7 16 4z"/><circle cx="16" cy="10" r="1.3"/><path d="M13.4 15 11 18h2.4z"/><path d="M18.6 15 21 18h-2.4z"/><path d="M14.7 17 16 21 17.3 17"/><path d="M9 25h14"/><path d="M12 25v-2M20 25v-2"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/smelter.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#b85a1e"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M9 9h14l-2.5 8h-9z"/><path d="M8 9h16"/><path d="M11 26c-1-1.8.4-3 .4-4 .9 1 1.6 2.2 1.6 4"/><path d="M16 26c-1-2 .4-3.4.4-4.4 .9 1 1.6 2.6 1.6 4.4"/><path d="M21 26c-1-1.8.4-3 .4-4 .9 1 1.6 2.2 1.6 4"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/splitter.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#7a7a5a"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M5 16h11"/><path d="M16 8v16"/><path d="M13.5 10.5 16 8 18.5 10.5"/><path d="M13.5 21.5 16 24 18.5 21.5"/>
+  </g>
+</svg>

bin/app/data/icons/buildings/tunnel_entry.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <rect width="100" height="100" rx="22" fill="#4f7562"/>
+  <g transform="translate(13,13) scale(2.3125)" fill="none" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M4 9h24"/><path d="M8 9C8 24 24 24 24 9"/><path d="M14.5 18.5 17.5 20 14.5 21.5"/>
+  </g>
+</svg>

bin/test/data/config/modules.toml

@@ -1,7 +1,6 @@
 [[module]]
 id = "armor_plate"
 tooltip = "Adds a large flat bonus to hit points."
-unlock_at_station_level = -1
 surface_mask = ["OO"]
 materials = [{item = "iron_ingot", amount = 2}]
 production_time_seconds = 3
@@ -13,7 +12,6 @@ multiplied_hp = 1.5
 
 [[module]]
 id = "sensor_booster"
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "circuit_board", amount = 1}]
 production_time_seconds = 2
@@ -25,7 +23,6 @@ added_sensor_range_m = 100
 
 [[module]]
 id = "weapon_upgrade"
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "iron_ingot", amount = 1}, {item = "circuit_board", amount = 1}]
 production_time_seconds = 4
@@ -37,7 +34,6 @@ multiplied_damage = 1.2
 
 [[module]]
 id = "laser_cannon"
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "iron_ingot", amount = 1}]
 production_time_seconds = 5
@@ -51,7 +47,6 @@ attack_rate_hz = 2.0
 
 [[module]]
 id = "salvager"
-unlock_at_station_level = -1
 surface_mask = ["OO"]
 materials = [{item = "iron_ingot", amount = 2}]
 production_time_seconds = 5
@@ -65,7 +60,6 @@ collection_rate_hz = 0.5
 
 [[module]]
 id = "repair_tool"
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "circuit_board", amount = 2}]
 production_time_seconds = 5
@@ -79,7 +73,6 @@ repair_range_m = 800
 
 [[module]]
 id = "weapon_primer"
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "iron_ingot", amount = 1}]
 production_time_seconds = 4
@@ -91,7 +84,6 @@ multiplied_attack_rate_hz = 1.2
 
 [[module]]
 id = "weapon_stabilizer"
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "iron_ingot", amount = 1}]
 production_time_seconds = 4
@@ -104,7 +96,6 @@ multiplied_attack_rate_hz = 0.8
 
 [[module]]
 id = "afterburner"
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "iron_ingot", amount = 1}]
 production_time_seconds = 2
@@ -117,7 +108,6 @@ added_main_acceleration_mpss = 60
 
 [[module]]
 id = "maneuvering_thrusters"
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "iron_ingot", amount = 1}]
 production_time_seconds = 2

bin/test/data/config/recipes.toml

@@ -43,7 +43,7 @@ duration_seconds = 4.0
 [[recipe]]
 id = "premium_circuit"
 building = "assembler"
-unlock_at_station_level = -1
+unlocked_at_start = true
 inputs = [{item = "circuit_board", amount = 1}]
 outputs = [{item = "premium_circuit", amount = 1}]
 duration_seconds = 8.0
@@ -51,7 +51,6 @@ duration_seconds = 8.0
 [[recipe]]
 id = "quick_circuit"
 building = "assembler"
-unlock_at_station_level = 0
 inputs = [{item = "copper_ingot", amount = 3}]
 outputs = [{item = "circuit_board", amount = 1}]
 duration_seconds = 3.0
@@ -59,7 +58,6 @@ duration_seconds = 3.0
 [[recipe]]
 id = "advanced_circuit"
 building = "assembler"
-unlock_at_station_level = 1
 inputs = [{item = "iron_ingot", amount = 5}]
 outputs = [{item = "circuit_board", amount = 1}]
 duration_seconds = 6.0
@@ -67,7 +65,6 @@ duration_seconds = 6.0
 [[recipe]]
 id = "exotic_alloy"
 building = "assembler"
-unlock_at_station_level = 0
 inputs = [{item = "exotic_ore", amount = 2}]
 outputs = [{item = "exotic_alloy", amount = 1}]
 duration_seconds = 10.0

bin/test/data/config/ships.toml

@@ -1,6 +1,5 @@
 [[ship]]
 id = "interceptor"
-unlock_at_station_level = -1
 layout = ["XOX", "OOO", "XOX"]
 default_modules = [{type = "laser_cannon", x = 1, y = 1, rotation = "east"}]
 
@@ -24,7 +23,6 @@ sensor_range_m = 2000
 
 [[ship]]
 id = "destroyer"
-unlock_at_station_level = -1
 layout = ["XOOX", "OOOO", "XOOX"]
 default_modules = [{type = "laser_cannon", x = 1, y = 1, rotation = "east"}]
 
@@ -48,7 +46,6 @@ sensor_range_m = 3000
 
 [[ship]]
 id = "salvage_ship"
-unlock_at_station_level = -1
 layout = ["OOO", "OOO"]
 
 [ship.schematic]
@@ -71,7 +68,6 @@ sensor_range_m = 2500
 
 [[ship]]
 id = "repair_ship"
-unlock_at_station_level = 0
 layout = ["XOX", "OOO", "XOX"]
 
 [ship.schematic]

bin/test/data/config/unlocks.toml

@@ -0,0 +1,21 @@
+# Unlock groups for the test config (REQ-LOCK-EXPLICIT). Mirrors the previous
+# per-item gating: repair_ship, quick_circuit, advanced_circuit start locked and
+# are awarded via defence station drops. exotic_alloy is intentionally NOT here:
+# it stays implicitly gated (its output/inputs are unreachable), so it is never
+# unlocked. premium_circuit uses unlocked_at_start in recipes.toml. Everything
+# else (interceptor, destroyer, salvage_ship, all modules) starts unlocked.
+
+[[unlock]]
+id = "repair_ship"
+station_level = 0
+ships = ["repair_ship"]
+
+[[unlock]]
+id = "quick_circuit"
+station_level = 0
+recipes = ["quick_circuit"]
+
+[[unlock]]
+id = "advanced_circuit"
+station_level = 1
+recipes = ["advanced_circuit"]

bin/test/data/config/world.toml

@@ -1,6 +1,7 @@
 [world]
 height_tiles = 60
 refund_percentage = 75
+deconstruction_time_seconds = 0.1
 starting_building_blocks = 100
 scrap_despawn_seconds = 30
 scrap_per_threat = 1.0

docs/architecture.md

@@ -15,7 +15,7 @@ This document captures the architectural decisions for the project. It is a comp
 A strict separation between the game simulation and the Qt Widgets UI.
 
 - The **simulation** is a pure C++ library that depends only on Qt Core and Qt Gui (QPoint, QVector2D, QRect, etc., as required by the coding guidelines), toml++, and tinyexpr. It contains no QtWidgets, no painting, and no QApplication. Note: in Qt 5, vector math types such as QVector2D live in Qt::Gui rather than Qt::Core, so the lib links both.
-- The **UI** reads simulation state and renders it. It owns all widgets, painting, and input handling, and drives the simulation via a small command interface (place building, demolish, clear belt tiles, change recipe, set game speed, etc.).
+- The **UI** reads simulation state and renders it. It owns all widgets, painting, and input handling, and drives the simulation via a small command interface (place building, deconstruct, clear belt tiles, change recipe, set game speed, etc.).
 
 This split is enforced at the CMake target level (see below). Tests link only against the simulation library and run without a display server.
 
@@ -93,7 +93,7 @@ Schematic drops: when an enemy station set is destroyed, the simulation generate
 
 ### UI Events
 
-All UI interactions — building selection, builder/blueprint mode transitions, speed changes, demolish 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()`.
+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`).
 
@@ -325,7 +325,7 @@ Sim and UI run on the same thread for v1. `paintEvent` reads sim state directly
 4. **Scrap** — glyphs at world positions.
 5. **Ships** — colored arrows oriented by velocity; color keyed to role (player combat / salvage / repair / enemy).
 6. **Laser beams** — lines derived from live `BeamFiredEvent`s kept by the renderer for 0.3 s, colored per `BeamKind` (weapon/repair/salvage) (REQ-SHP-FIRING-BEAM).
-7. **Build overlays** — ghost in builder mode (REQ-BLD-GHOST), demolish-mode tint, tile highlight under cursor, box-drag selection rectangle.
+7. **Build overlays** — ghost in builder mode (REQ-BLD-GHOST), deconstruct-mode tint, tile highlight under cursor, box-drag selection rectangle.
 8. **Screen-space UI** — screen-anchored elements, drawn after resetting the world-space transform.
 
 ### Coordinates and Scrolling
@@ -372,7 +372,7 @@ width_px = 2
 [overlays]
 ghost_valid    = "#ffffff44"
 ghost_invalid  = "#ff000044"
-demolish_tint  = "#ff000033"
+deconstruct_tint  = "#ff000033"
 selection_rect = "#00ff00"
 
 [toast]

docs/replay_design.md

@@ -55,7 +55,7 @@ data, not the UI gesture. Example: placing a miner records
 One command per sim-mutating operation (the complete mutation surface):
 
 - `PlaceBuilding`
-- `Demolish`
+- `Deconstruct`
 - `RotateInPlace`
 - `SetRecipe`
 - `SetShipLayout`
@@ -125,7 +125,7 @@ the only way production code can reach them is `apply(command)`.
 > `BeltSystem` directly, and every production `buildings()`/`belts()` call is a const query.
 > So:
 >
-> - `Simulation::tryPlaceBuilding`, `demolish`, and `applySchematicChoice` are **private**.
+> - `Simulation::tryPlaceBuilding`, `deconstruct`, and `applySchematicChoice` are **private**.
 > - The mutable subsystem accessors are private and renamed `buildingsMutable()` /
 >   `beltsMutable()`; only `const BuildingSystem& buildings() const` / `belts() const` are
 >   public (queries). UI query sites bind to the const overload unchanged.
@@ -377,7 +377,7 @@ The whole feature rests on a deterministic sim, so prove that before building on
 
 Reshape mutations to flow through one path; behaviour unchanged.
 
-- Defined `Command` base + derived types (`PlaceBuilding`, `Demolish`, `RotateInPlace`,
+- Defined `Command` base + derived types (`PlaceBuilding`, `Deconstruct`, `RotateInPlace`,
   `SetRecipe`, `SetShipLayout`, `SetSiteSplitterFilters`, `SetSplitterFilters`,
   `ClearBeltTiles`, `ApplySchematicChoice`, `Reset`) in `lib`, each with a `playerId` (always 0
   now). `PlaceBuilding` is atomic (carries optional config — see the refinement note above).

docs/requirements.md

@@ -4,11 +4,12 @@
 
 Config files use the TOML format. The following config files drive game parameters:
 
-- **world.toml** — world dimensions, region widths, expansion amounts, building refund percentage, 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).
-- **recipes.toml** — crafting recipes: inputs, outputs, quantities, durations, and reprocessing plant probabilities. Assembler recipe entries may optionally define `unlock_at_station_level` (integer): -1 means the recipe is explicitly unlocked at game start; a value ≥ 0 means the recipe starts locked and a schematic for it can be awarded via defence station destruction (see REQ-LOCK-EXPLICIT, REQ-DEF-SCHEMATIC-DROP). An assembler recipe schematic entry may also define an optional `unlock_requires` list of prerequisite schematic ids (REQ-LOCK-PREREQ).
-- **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, the station level at which the schematic becomes available for unlock (`unlock_at_station_level`; -1 means the player starts with the schematic already unlocked), an optional `unlock_requires` prerequisite list (REQ-LOCK-PREREQ), a layout grid defining the ship's module slots, and a `default_modules` list used for enemy wave ships (see REQ-WAV-DEFAULT-MODULES).
-- **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), the station level at which the schematic becomes available for unlock (`unlock_at_station_level`; -1 means the player starts with the module schematic already unlocked), an optional `unlock_requires` prerequisite list (REQ-LOCK-PREREQ), and an optional capability section and/or stat modifier formulas. 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).
+- **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).
+- **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.
 - **visuals.toml** — rendering-only config (not game parameters): fill and outline colors and glyphs for every building type, item type, ship schematic, and station type; a distinct beam color per tool type (weapon, repair, salvage) and beam width; overlay and toast colors; and building status light colors (grey, green, red, and yellow fills plus the outline color, REQ-UI-STATUS-LIGHT). Loaded by the UI at startup; the simulation does not read it.
 - **ship_layouts.toml** — named layout blueprints per ship type; written and read by the application to persist the layout blueprint panel (REQ-MOD-UI-BLUEPRINT-PANEL through REQ-MOD-UI-BLUEPRINT-FILE-LOAD). Not a game parameter file; the simulation does not read it.
@@ -65,6 +66,28 @@ Modules in `modules.toml` define a `surface_mask` — a list of strings that des
 - `O` — module cell: must be placed on an unoccupied buildable cell (`O`) of the ship's layout.
 - `X` — ignored cell: may overlap any cell (non-buildable, unoccupied buildable, or occupied buildable) or extend outside the layout grid entirely.
 
+### Unlock Group Format
+
+Unlock groups in `unlocks.toml` define what the player can be awarded from defence station drops (REQ-DEF-SCHEMATIC-DROP); by their absence they also define what is available from game start (REQ-LOCK-EXPLICIT). Each entry:
+
+```toml
+[[unlock]]
+id = "salvage_operations"           # unique unlock-group id
+station_level = 2                   # eligible once a destroyed station set's level >= this
+requires = []                       # prerequisite unlock-group ids (REQ-LOCK-PREREQ); default empty
+ships = []                          # ship schematic ids granted (from ships.toml)
+modules = ["salvager"]              # module schematic ids granted (from modules.toml)
+buildings = ["salvage_bay"]         # building type ids granted (from buildings.toml)
+recipes = []                        # assembler recipe ids granted (from recipes.toml)
+```
+
+- `id` — unique identifier of the unlock group; referenced by other groups' `requires`. Its display name in the schematic choice dialog is derived from the id (same convention as building, module, and recipe ids); there is no separate name field for now.
+- `station_level` — the minimum destroyed enemy defence station level at which this group becomes eligible to drop (REQ-DEF-SCHEMATIC-DROP).
+- `requires` — optional list of prerequisite unlock-group ids that must already have been awarded before this group can drop (REQ-LOCK-PREREQ). Defaults to empty.
+- `ships`, `modules`, `buildings`, `recipes` — the ids granted when this group is awarded. Each list defaults to empty, but a group must grant at least one item overall. Every id must resolve to a definition in the corresponding config file, and `recipes` ids must name **assembler** recipes. Each grantable id (ship, module, building, or assembler recipe) may be granted by **at most one** unlock group; violations fail config load (REQ-LOCK-EXPLICIT).
+
+Any ship, module, building, or assembler recipe id that appears in no unlock group's grant lists is available from game start (REQ-LOCK-EXPLICIT).
+
 ## 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.
@@ -105,7 +128,7 @@ Modules in `modules.toml` define a `surface_mask` — a list of strings that des
 - 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 demolishing 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-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-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.
@@ -119,11 +142,12 @@ Modules in `modules.toml` define a `surface_mask` — a list of strings that des
   - **Resolving the type.** If neither match exists, the ghost is a Tunnel Entry (the default). If only one kind of match exists, the ghost is the kind that produces it (Tunnel Exit for an exit-completion match, Tunnel Entry for an entry-completion match). If **both** an exit-completion match (an existing Entry) and an entry-completion match (an existing Exit) exist, the mode resolves to the completion whose **existing partner building is closer to the mouse cursor position** — the actual sub-tile cursor position, not the hovered tile's center — and the ghost becomes the corresponding type (a Tunnel Exit to complete the nearer Entry, or a Tunnel Entry to complete the nearer Exit). Because the comparison uses the sub-tile cursor position, when the two partners are at the same tile distance the player can move the cursor within the hovered tile to switch which end is placed. When more than one candidate qualifies on a side, the nearest qualifying partner on that side is used.
   - **Connection preview (green).** Whenever a completion match is resolved, the matched existing partner building is highlighted green, and every tile strictly between that partner and the hovered ghost tile (along the tunnel's straight run) is marked green, previewing the connection that placing the ghost would create.
   - **Invalid positions.** The completion tests, type switch, and green preview apply only while the hovered position is a valid placement (REQ-BLD-PLACE-VALID). At an invalid position the ordinary invalid-colored ghost is shown (REQ-BLD-GHOST) with no green preview and no switch away from the default Tunnel Entry.
-- REQ-BLD-DEMOLISH: The player can demolish a placed factory building. Demolition returns `world.toml [world].refund_percentage` percent of the original building block cost (default 75%) to the global stock. Exception: if the building is still in the construction queue (not yet fully built, including the one currently being constructed), it is removed from the queue and the **full** building block cost is refunded. The HQ and player defence stations cannot be demolished.
-- REQ-BLD-DEMOLISH-CLICK: While in demolish mode (REQ-UI-HOTKEYS, REQ-UI-DEMOLISH-BUTTON), left-clicking a placed factory building or construction site in the game world demolishes it, following the refund rules of REQ-BLD-DEMOLISH — the partial refund for built buildings and the full refund for still-queued construction sites. Clicking a building that cannot be demolished (the HQ or a player defence station, per REQ-BLD-DEMOLISH), or clicking empty world space, has no effect. Demolish mode stays active after a demolition so the player can demolish further buildings without re-entering the mode; it is exited via the Q toggle (REQ-UI-HOTKEYS) or the Demolish button (REQ-UI-DEMOLISH-BUTTON).
-- REQ-BLD-DEMOLISH-BOX: While in demolish mode (REQ-UI-HOTKEYS, REQ-UI-DEMOLISH-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, every placed factory building and construction site covered by the box is demolished, each following the refund rules of REQ-BLD-DEMOLISH — the partial refund for built buildings and the full refund for still-queued construction sites. Buildings that cannot be demolished (the HQ and player defence stations, per REQ-BLD-DEMOLISH) are excluded from the box demolition; ships and defence stations are never affected.
+- REQ-BLD-DECONSTRUCT: The player can deconstruct a placed factory building. Deconstructing a **fully-built** factory building does not remove it instantly: it is added to the deconstruction queue (REQ-BLD-DECON-QUEUE) and, once its deconstruction completes, `world.toml [world].refund_percentage` percent of the original building block cost (default 75%) is returned to the global stock. Exception: if the building is still in the construction queue (not yet fully built, including the one currently being constructed), it is **not** queued for deconstruction but removed instantly from the construction queue, and the **full** building block cost is refunded immediately. The HQ and player defence stations cannot be deconstructed.
+- REQ-BLD-DECON-QUEUE: Fully-built factory buildings marked for demolition (REQ-BLD-DECONSTRUCT) enter a **deconstruction queue** that is processed one building at a time and runs in parallel with the construction queue (REQ-BLD-QUEUE) — the two queues advance independently and simultaneously. Each building takes `world.toml [world].deconstruction_time_seconds` (default 0.1) to deconstruct, the same duration for every building type. When a building's deconstruction completes it is removed from the world and its refund is credited (REQ-BLD-DECONSTRUCT). A building **stops operating the moment it enters the queue**: it runs no production and transports no items, and no longer participates as a live building (its tunnel pairing is re-evaluated as if it were gone, REQ-BLD-TUNNEL-PAIR), but it still physically occupies its tiles until removed, so those tiles stay blocked for placement. A queued building can be taken back out of the deconstruction queue before it is removed (REQ-BLD-DECONSTRUCT-CLICK, REQ-BLD-DECONSTRUCT-BOX) — including the one currently being deconstructed; doing so discards any deconstruction progress, credits no refund, and the building resumes operating (and re-pairs, REQ-BLD-TUNNEL-PAIR). Construction sites never enter the deconstruction queue (REQ-BLD-DECONSTRUCT). Every building in the deconstruction queue is rendered with the deconstruct tint — the `visuals.toml [overlays].deconstruct_tint` color, the same tint applied to a building hovered in deconstruct mode (REQ-UI-DECONSTRUCT-BORDER) — so queued buildings are visually distinct.
+- REQ-BLD-DECONSTRUCT-CLICK: While in deconstruct mode (REQ-UI-HOTKEYS, REQ-UI-DECONSTRUCT-BUTTON), left-clicking a placed factory building or construction site in the game world marks it for demolition, following the rules of REQ-BLD-DECONSTRUCT: a fully-built building is added to the deconstruction queue (REQ-BLD-DECON-QUEUE), and a construction site is removed instantly with the full refund. Left-clicking a fully-built building that is **already in the deconstruction queue** instead removes it from the queue (un-queues it, REQ-BLD-DECON-QUEUE), with no refund; repeated clicks on the same building therefore alternate between queueing and un-queueing it. Clicking a building that cannot be deconstructed (the HQ or a player defence station, per REQ-BLD-DECONSTRUCT), or clicking empty world space, has no effect. Deconstruct mode stays active after each action so the player can continue without re-entering the mode; it is exited via the Q toggle (REQ-UI-HOTKEYS) or the Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON).
+- REQ-BLD-DECONSTRUCT-BOX: While in deconstruct mode (REQ-UI-HOTKEYS, REQ-UI-DECONSTRUCT-BUTTON), the player can click and drag a selection box in the game world. A selection rectangle is drawn while dragging, using the same box-drag gesture and coverage semantics as the multi-select box (REQ-UI-MULTI-SELECT). On mouse up, following the rules of REQ-BLD-DECONSTRUCT: every construction site covered by the box is removed instantly with the full refund; and among the fully-built deconstructible buildings covered by the box, if **all** of them are already in the deconstruction queue they are all removed from it (un-queued, REQ-BLD-DECON-QUEUE), otherwise every covered building not yet in the queue is added to the deconstruction queue (already-queued ones stay). Buildings that cannot be deconstructed (the HQ and player defence stations, per REQ-BLD-DECONSTRUCT) are excluded from the box demolition; ships and defence stations are never affected.
 - REQ-BLD-SITE-CONFIG: A construction site — a building that has been placed but is still queued or under construction (REQ-BLD-QUEUE) — can be selected and configured exactly like the equivalent operational building, before it finishes building. Whatever configuration the building type supports is available on the site: the recipe for a Miner or Assembler (REQ-UI-SELECT-BUTTON), the produced-ship schematic and its module layout for a Shipyard (REQ-UI-SELECT-BUTTON, REQ-MOD-UI-PREVIEW, REQ-MOD-UI-DIALOG), and the output filters for a Splitter (REQ-BLD-SPLITTER) — all set through the same Selected Building Panel controls (REQ-UI-CONFIG-INLINE). Only currently unlocked recipes and schematics are offered, exactly as for operational buildings (REQ-LOCK-UI-RECIPE, REQ-LOCK-UI-SCHEMATIC, REQ-LOCK-UI-SPLITTER). The configuration is stored on the construction site and carries over unchanged when construction completes, so the building becomes operational already configured. A construction site has no input/output buffers and runs no production cycle, so the buffer and production-progress portions of the panel (REQ-UI-SINGLE-SELECTION, REQ-UI-PRODUCTION-PROGRESS) are not shown for it; only its construction progress (REQ-UI-CONSTRUCTION-PROGRESS) and its configuration controls appear. (Blueprint placement already applies a stored recipe or schematic to a construction site on placement per REQ-UI-BLUEPRINT-PLACE; this requirement additionally lets the player set or change that configuration directly on an existing site.)
-- REQ-BLD-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 demolish mode is active it is disabled, so it never clashes with placement or demolition clicks.
+- 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.
@@ -147,12 +171,12 @@ Modules in `modules.toml` define a `surface_mask` — a list of strings that des
   - In all alternation cases, if one output is blocked the item goes to the other output until it unblocks.
 - REQ-BLD-TUNNEL-ENTRY: **Tunnel Entry** (1×1): The sending end of a tunnel pair. The player sets a direction (N, S, E, W) at placement, rotatable with R/Shift+R. Items arriving from an adjacent belt tile on a non-output edge (i.e. not the mouth edge in the entry's facing direction — see REQ-MAT-ACCEPT-DIR) whose direction points into the entry are forwarded through the tunnel to the paired Tunnel Exit (see REQ-BLD-TUNNEL-PAIR, REQ-BLD-TUNNEL-TRANSIT). If the entry is unpaired, or if the paired exit's output is blocked, the entry blocks like a full belt tile.
 - REQ-BLD-TUNNEL-EXIT: **Tunnel Exit** (1×1): The receiving end of a tunnel pair. The player sets a direction at placement, rotatable with R/Shift+R. Items received from the paired Tunnel Entry emerge from the output side of the exit tile — the tile adjacent in the exit's facing direction — continuing in that direction. If the exit is unpaired or its output is blocked, it holds received items until they can advance.
-- REQ-BLD-TUNNEL-PAIR: **Tunnel pairing rules.** Pairing is re-evaluated for all Tunnel Entries whenever any Tunnel Entry or Tunnel Exit is placed or demolished.
+- REQ-BLD-TUNNEL-PAIR: **Tunnel pairing rules.** Pairing is re-evaluated for all Tunnel Entries whenever any Tunnel Entry or Tunnel Exit is placed, deconstructed, or enters or leaves the deconstruction queue (REQ-BLD-DECON-QUEUE; a tunnel end that is queued for deconstruction counts as removed for pairing).
   - A Tunnel Entry searches tile-by-tile in its facing direction for a partner. Any tunnel building (entry or exit) that faces a *different* direction is ignored and skipped. The search stops at the first tunnel building that faces the *same* direction as the searching entry.
   - If that first same-direction tunnel building is a Tunnel Exit, is within `tunnel_max_distance` tiles of the entry, and is not already paired with a closer entry, the two form a pair.
   - Otherwise the entry is unpaired.
   - Pairing is one-to-one: each Tunnel Entry pairs with at most one Tunnel Exit, and vice versa. A Tunnel Exit is claimed by the nearest Tunnel Entry that can validly reach it; all other entries for which it would otherwise qualify are unpaired.
-  - When one end of a pair is demolished, the pair is dissolved and any items currently in transit are discarded.
+  - When one end of a pair is deconstructed, the pair is dissolved and any items currently in transit are discarded.
 - REQ-BLD-TUNNEL-TRANSIT: **Tunnel transit.** Items inside a tunnel are not rendered (they travel invisibly). Transit time equals the tile-coordinate distance between entry and exit divided by `world.toml [world].belt_speed_tiles_per_second`, matching the time a chain of belt tiles of equivalent length would take. Multiple items may be in transit simultaneously, spaced as they would be on a belt chain of the same length. Clearing a tunnel entry or exit tile (REQ-UI-BELT-CLEAR) also discards all items currently in transit through that tunnel.
 - REQ-BLD-TUNNEL-SELECT-HIGHLIGHT: **Selected-tunnel connection highlight.** While a Tunnel Entry or Tunnel Exit — operational building or construction site — is part of the current selection (single selection or multi-selection, REQ-UI-MULTI-SELECT), its tunnel connection is marked green in the game world, using the same `visuals.toml [overlays].tunnel_preview` green as the placement connection preview (REQ-BLD-TUNNEL-MODE). The matching end is found by applying the pairing scan of REQ-BLD-TUNNEL-PAIR over both built tunnels **and** construction-site tunnels (site-inclusive, matching the placement preview): for a selected entry, the first same-direction tunnel within `tunnel_max_distance` along its facing direction, if it is a Tunnel Exit; for a selected exit, the first same-direction tunnel within `tunnel_max_distance` opposite its facing direction, if it is a Tunnel Entry. When a matching end is found, the entry tile, the exit tile, and every tile strictly between them (along the tunnel's straight run) are marked green. A selected tunnel with no matching end shows no green highlight (it still receives the normal selection outline). In multi-selection each selected tunnel end that has a matching end contributes its connection, and a given connection is shown whenever either of its ends is selected. The highlight is presentation-only and has no effect on the simulation.
 
@@ -193,7 +217,7 @@ Modules in `modules.toml` define a `surface_mask` — a list of strings that des
 ## Ships
 
 - REQ-SHP-AUTONOMOUS: Ships are produced by shipyards and are fully autonomous once produced.
-- REQ-SHP-STATS: Base hull stats are defined as plain values in `ships.toml`: HP (`[ship.health].hp`), max linear speed (`[ship.movement].speed`), sensor range (`[ship.sensors].range`), main acceleration (`[ship.movement].main_acceleration`, tiles/s²), maneuvering acceleration (`[ship.movement].maneuvering_acceleration`, tiles/s²), angular acceleration (`[ship.movement].angular_acceleration`, rad/s²), max rotation speed (`[ship.movement].max_rotation_speed`, rad/s). Required build materials (`[ship.schematic].materials`) and the station level at which the schematic becomes available for unlock (`[[ship]].unlock_at_station_level`; -1 = player starts with the schematic already unlocked) are also defined there. Combat, salvage, and repair capabilities are provided by modules (see REQ-MOD-CONFIG). Final hull stats incorporate passive module modifiers per REQ-MOD-STAT-CALC.
+- REQ-SHP-STATS: Base hull stats are defined as plain values in `ships.toml`: HP (`[ship.health].hp`), max linear speed (`[ship.movement].speed`), sensor range (`[ship.sensors].range`), main acceleration (`[ship.movement].main_acceleration`, tiles/s²), maneuvering acceleration (`[ship.movement].maneuvering_acceleration`, tiles/s²), angular acceleration (`[ship.movement].angular_acceleration`, rad/s²), max rotation speed (`[ship.movement].max_rotation_speed`, rad/s). Required build materials (`[ship.schematic].materials`) are also defined there; whether the schematic starts unlocked or must be awarded during play is defined in `unlocks.toml` (REQ-LOCK-EXPLICIT). Combat, salvage, and repair capabilities are provided by modules (see REQ-MOD-CONFIG). Final hull stats incorporate passive module modifiers per REQ-MOD-STAT-CALC.
 - REQ-SHP-SPAWN-PLAYER: A ship produced by a shipyard spawns centered on the shipyard's output port tile.
 - REQ-SHP-SPAWN-ENEMY: Enemy ships spawn at a uniformly random position within the current enemy buffer zone — random X across the buffer's width and random Y across the world height.
 - REQ-SHP-MOVEMENT: Ships move using a physics-based model. Each ship has a velocity and a facing direction, both updated each tick. The main acceleration (`main_acceleration`) is applied along the ship's current facing direction only. The maneuvering acceleration (`maneuvering_acceleration`) can be applied in any direction independently of the facing direction, enabling lateral or braking movement without rotating. The angular acceleration (`angular_acceleration`) controls how quickly the ship rotates. Linear speed is capped at the ship's `speed` value; rotation rate is capped at the ship's `max_rotation_speed` value. Ship position refers to the ship's center for all range, sensor, and attack checks.
@@ -234,8 +258,6 @@ Modules in `modules.toml` define a `surface_mask` — a list of strings that des
   - `id` — unique identifier, also used as the display name in the UI.
   - `surface_mask` — footprint within the ship layout grid (see Module Surface Mask Format).
   - `materials` — list of materials required per instance (added to the ship's build cost).
-  - `unlock_at_station_level` — the enemy defence station level at which this module's schematic becomes available for unlock; -1 means the player starts with the module schematic already unlocked.
-  - `unlock_requires` — optional list of prerequisite schematic ids that must already be unlocked before this module's schematic can drop (REQ-LOCK-PREREQ). Defaults to empty.
   - `production_time_seconds` — time added to the ship's production cycle per instance.
   - `fill_color` — fill color used to render this module's cells in the layout grid.
   - `glyph` — single character rendered on this module's cells in the layout grid and preview widget.
@@ -349,35 +371,27 @@ Modules in `modules.toml` define a `surface_mask` — a list of strings that des
 - REQ-DEF-ENEMY-FIRE: Enemy defence stations automatically fire at player ships within range.
 - REQ-DEF-NO-CROSSFIRE: Enemy and player defence stations are never in each other's firing range.
 - REQ-DEF-PUSH: When both enemy defence stations in a set are destroyed, the boss countdown is advanced (REQ-WAV-BOSS-ADVANCE), the scrollable area is extended (REQ-GW-PUSH-EXPAND), a new set of enemy defence stations is placed at the new boundary, and exactly one schematic drop is awarded for the destroyed set (REQ-DEF-SCHEMATIC-DROP).
-- REQ-DEF-SCHEMATIC-DROP: Each destroyed set of enemy defence stations awards exactly one schematic drop (not one per station). The drop opens a **schematic choice dialog** — a modal dialog that pauses the game (speed set to 0×; on close, speed is restored to what it was before the dialog opened). Before drawing schematic picks, an artifact roll is made: evaluate `world.toml [world].artifact_chance_formula` with `x` set to the level of the destroyed station set, clamp the result to [0, 1], then compare against a uniform random value in [0, 1). If the roll succeeds, the dialog presents one **artifact option** plus two schematic picks drawn from the eligible pool; otherwise it presents three schematic picks. Up to three (or two, if an artifact option is present) schematic options are drawn uniformly at random **without replacement** from the eligible drop pool. If the pool contains fewer than the required number of entries, only that many schematic options are shown (the artifact option is always shown if the roll succeeded). The eligible drop pool contains:
-  - All **ship schematics** and **module schematics** whose `unlock_at_station_level` is ≥ 0 and ≤ the level of the destroyed station set, and which have not yet been unlocked.
-  - All **assembler recipe schematics** whose `unlock_at_station_level` is ≥ 0 and ≤ the level of the destroyed station set, whose output item is currently implicitly unlocked (REQ-LOCK-IMPLICIT), and which have not yet been awarded.
+- REQ-DEF-SCHEMATIC-DROP: Each destroyed set of enemy defence stations awards exactly one drop (not one per station). The drop opens a **schematic choice dialog** — a modal dialog that pauses the game (speed set to 0×; on close, speed is restored to what it was before the dialog opened). Before drawing picks, an artifact roll is made: evaluate `world.toml [world].artifact_chance_formula` with `x` set to the level of the destroyed station set, clamp the result to [0, 1], then compare against a uniform random value in [0, 1). If the roll succeeds, the dialog presents one **artifact option** plus two unlock picks drawn from the eligible pool; otherwise it presents three unlock picks. Up to three (or two, if an artifact option is present) unlock options are drawn uniformly at random **without replacement** from the eligible pool. If the pool contains fewer than the required number of entries, only that many unlock options are shown (the artifact option is always shown if the roll succeeded).
 
-  In addition to the conditions above, a schematic is included in the eligible drop pool only when every prerequisite in its optional `unlock_requires` list is currently satisfied (REQ-LOCK-PREREQ). Because the pool is rebuilt for each drop, a schematic gated behind prerequisites first appears only after all of its prerequisites have themselves been unlocked.
+  The eligible pool contains every **unlock group** (REQ-LOCK-EXPLICIT) that (a) has not yet been awarded, (b) whose `station_level` is ≤ the level of the destroyed station set, and (c) every prerequisite in its `requires` list is currently satisfied (REQ-LOCK-PREREQ). Because the pool is rebuilt for each drop, an unlock group gated behind prerequisites first appears only after all of its prerequisites have themselves been awarded.
 
-  Each option in the dialog displays: the schematic name (ship `id` from `ships.toml`, module `id` from `modules.toml`, or assembler recipe `id` from `recipes.toml`) and the schematic type (ship, module, or assembler recipe). The artifact option (if present) is displayed as a distinct entry with the name "Artifact".
+  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 assembler recipes (without `unlock_at_station_level`) that are not currently implicitly unlocked but would become so after applying this option's effect:
-  - For a ship or module schematic, its `materials` are added to the base set per REQ-LOCK-IMPLICIT step 1a before recomputation.
-  - For an assembler recipe schematic, its output item is added to the base set per REQ-LOCK-IMPLICIT step 1b before recomputation.
+  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 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".
 
-  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 schematic is applied. Otherwise, the selected schematic is applied and the dialog closes:
-
-  For a **ship or module schematic**: it is unlocked (ship schematics unlock the corresponding shipyard selection; module schematics unlock the module type for placement in the layout configuration dialog (REQ-MOD-UI-DIALOG)).
-
-  For an **assembler recipe schematic**: the recipe is explicitly unlocked and becomes available in the assembler recipe-selection dialog (subject to REQ-LOCK-UI-RECIPE). The schematic is removed from the drop pool permanently (REQ-LOCK-EXPLICIT). The implicit unlock set is recomputed (REQ-LOCK-IMPLICIT).
+  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).
 
 ## Progression & Locking
 
-- REQ-LOCK-EXPLICIT: Ship schematics, module schematics, and **assembler recipe schematics** (assembler recipes in `recipes.toml` that define `unlock_at_station_level`) are **explicitly** locked or unlocked. A schematic starts unlocked if its `unlock_at_station_level` is -1; all others start locked. Locked schematics are unlocked only by REQ-DEF-SCHEMATIC-DROP. Once unlocked, a schematic is never re-locked within a run; lock states reset to their initial values on Restart (REQ-CFG-RELOAD). Unlike ship and module schematics, an assembler recipe schematic is removed from the drop pool permanently once awarded and cannot be dropped again.
+- REQ-LOCK-EXPLICIT: The unit of unlocking is an **unlock group**, defined by an `[[unlock]]` entry in `unlocks.toml` (see Unlock Group Format). Each unlock group grants a set of ship schematics, module schematics, building types, and/or assembler recipes. A ship, module, building, or assembler recipe is **locked at game start if and only if some unlock group grants it**; anything not granted by any unlock group starts unlocked. (For assembler recipes this "starts unlocked" is further governed by implicit gating — see REQ-LOCK-IMPLICIT; an assembler recipe granted by an unlock group is explicitly gated and never subject to implicit unlocking, while one flagged `unlocked_at_start` is always available.) A locked item is unlocked only by awarding its unlock group via REQ-DEF-SCHEMATIC-DROP, which grants all of the group's members at once. Once awarded, an unlock group and its members are never re-locked within a run, and the group is removed from the drop pool permanently; lock states reset to their initial values on Restart (REQ-CFG-RELOAD). Each grantable id may be granted by **at most one** unlock group; a grant id that names no defined ship/module/building/assembler-recipe, that names a non-assembler recipe, or that is granted by more than one unlock group, is a configuration error that fails config load with a descriptive message (REQ-CFG-RELOAD).
 
-- REQ-LOCK-PREREQ: A ship schematic, module schematic, or assembler recipe schematic may optionally define `unlock_requires` — a list of prerequisite schematic ids (a ship `id`, module `id`, or assembler recipe `id`) that must already be unlocked before this schematic may enter the drop pool. A prerequisite is **satisfied** only when the schematic it names is currently **explicitly unlocked** (REQ-LOCK-EXPLICIT) — that is, the referenced schematic either started unlocked with `unlock_at_station_level = -1` or has been awarded via a drop. This prerequisite check is applied in addition to the per-schematic conditions in REQ-DEF-SCHEMATIC-DROP: a schematic enters the eligible drop pool only when its `unlock_at_station_level` condition is met, it has not yet been unlocked/awarded, and every id in its `unlock_requires` is satisfied. `unlock_requires` defaults to empty (no prerequisites), which reproduces the prior behaviour. The check is re-evaluated against the current explicit-unlock set every time a drop pool is built (after each REQ-DEF-SCHEMATIC-DROP and on Restart per REQ-CFG-RELOAD), so a gated schematic becomes eligible in the first drop after its last prerequisite is unlocked. Every id listed in any `unlock_requires` must resolve to a schematic that is itself explicitly unlockable (a ship, module, or assembler recipe schematic defined in config); an id that names no such schematic is a configuration error that fails config load with a descriptive message (config is loaded at startup and reloaded on Restart, REQ-CFG-RELOAD). A schematic that lists itself, or a cycle of mutually dependent prerequisites, is not a load error but can never become eligible, since no schematic in the cycle can be the first to unlock.
+- REQ-LOCK-PREREQ: An unlock group may optionally define `requires` — a list of prerequisite **unlock-group ids** that must already have been awarded before this group may enter the drop pool. A prerequisite is **satisfied** only when the unlock group it names has been awarded (REQ-LOCK-EXPLICIT). This check is applied in addition to the conditions in REQ-DEF-SCHEMATIC-DROP: a group enters the eligible pool only when its `station_level` condition is met, it has not yet been awarded, and every id in its `requires` is satisfied. `requires` defaults to empty (no prerequisites). The check is re-evaluated against the current set of awarded unlock groups every time a drop pool is built (after each REQ-DEF-SCHEMATIC-DROP and on Restart per REQ-CFG-RELOAD), so a gated group becomes eligible in the first drop after its last prerequisite is awarded. Every id listed in any `requires` must resolve to an unlock group defined in `unlocks.toml`; an id that names no such group is a configuration error that fails config load with a descriptive message (config is loaded at startup and reloaded on Restart, REQ-CFG-RELOAD). An unlock group that lists itself, or a cycle of mutually dependent prerequisites, is not a load error but can never become eligible, since no group in the cycle can be the first to be awarded.
 
 - REQ-LOCK-IMPLICIT: Item types and miner/assembler recipes are **implicitly** unlocked or locked based on the current set of unlocked ship, module, and assembler recipe schematics. The implicit unlock set is recomputed whenever any schematic changes lock state (on Restart or after REQ-DEF-SCHEMATIC-DROP). Computation:
-  1. Start with the union of: (a) all item types listed in `materials` across all currently unlocked ship schematics and all currently unlocked module schematics, and (b) the output item type of every currently explicitly unlocked assembler recipe schematic (REQ-LOCK-EXPLICIT).
-  2. For each item type in the current set: for every recipe (miner, smelter, or assembler) that produces it — skipping any assembler recipe schematic that defines `unlock_at_station_level` and is not yet explicitly unlocked — add each of that recipe's input item types to the set. If the recipe is a miner recipe or an assembler recipe that does not define `unlock_at_station_level`, mark it as implicitly unlocked. Explicitly unlocked assembler recipe schematics are available in the assembler recipe-selection dialog by virtue of REQ-LOCK-EXPLICIT; their inputs are also added to the implicit set in this step.
+  1. Start with the union of: (a) all item types listed in `materials` across all currently unlocked ship schematics and all currently unlocked module schematics, and (b) the output item type of every assembler recipe that is currently **explicitly available** — that is, either flagged `unlocked_at_start` in `recipes.toml`, or granted by an unlock group that has been awarded (REQ-LOCK-EXPLICIT).
+  2. For each item type in the current set: for every recipe (miner, smelter, or assembler) that produces it — skipping any assembler recipe that is granted by an unlock group whose group has not yet been awarded — add each of that recipe's input item types to the set. If the recipe is a miner recipe, or an assembler recipe that is not granted by any unlock group, mark it as implicitly unlocked. Assembler recipes that are explicitly available (flagged `unlocked_at_start`, or granted by an awarded unlock group) are available in the assembler recipe-selection dialog by virtue of REQ-LOCK-EXPLICIT; their inputs are also added to the implicit set in this step.
   3. Repeat step 2 until no new item types are added.
   Item types and miner/assembler recipes not reached by this process (and not explicitly unlocked) are locked. Smelter recipes participate in the traversal to propagate unlocking to their inputs but are never themselves shown in any UI dropdown.
 
@@ -387,9 +401,11 @@ Modules in `modules.toml` define a `surface_mask` — a list of strings that des
 
 - 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-UI-SPLITTER: Item types that are not implicitly unlocked are excluded from splitter filter dropdowns (REQ-BLD-SPLITTER).
 
-- REQ-LOCK-UI-BLUEPRINT: When a blueprint is placed (REQ-UI-BLUEPRINT-PLACE): if a stored recipe ID for a miner or assembler is currently locked, that building's recipe is left unset rather than applied; if a stored splitter filter entry refers to a locked item type, that entry is silently removed. (The analogous rule for locked ship schematics is defined in REQ-UI-BLUEPRINT-PLACE.)
+- REQ-LOCK-UI-BLUEPRINT: When a blueprint is placed (REQ-UI-BLUEPRINT-PLACE): if a building in the blueprint is of a currently locked building type (REQ-LOCK-BUILDING), that building is silently skipped — no ghost, no validity check, no construction site, and its cost is excluded from the total — exactly as if it were not part of the blueprint; if a stored recipe ID for a miner or assembler is currently locked, that building's recipe is left unset rather than applied; if a stored splitter filter entry refers to a locked item type, that entry is silently removed. (The analogous rule for locked ship schematics is defined in REQ-UI-BLUEPRINT-PLACE.)
 
 ## Threat Level & Enemy Waves
 
@@ -442,7 +458,7 @@ The screen is divided into two columns: a main column (75% width) containing the
 - REQ-UI-BOSS-STATUS: The header bar displays, to the left of the speed buttons, the current boss wave counter (REQ-WAV-BOSS-COUNTER) and the time remaining on the boss countdown (REQ-WAV-BOSS-COUNTDOWN). The boss wave counter is shown as `Boss Wave #<x>` and the countdown as `Next boss: <M:SS>`, where `<M:SS>` is the remaining seconds formatted as whole minutes and two-digit seconds. Both values update continuously as the simulation runs.
 - REQ-UI-SPEED: The game speed controls in the header bar are buttons for 0×, 0.5×, 1×, 2×, and 10× speed. The currently active speed is shown as selected. All game simulation (production, movement, threat accumulation, wave timing) scales with the selected speed. 0× pauses the game.
 - 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-DEMOLISH-BORDER: While demolish mode is active (REQ-UI-DEMOLISH-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 demolish 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].demolish_tint`, the same demolish-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 demolish mode, both vignettes are drawn and compose over each other.
+- 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> Blocks`, 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). 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).
@@ -476,7 +492,7 @@ The screen is divided into two columns: a main column (75% width) containing the
   - **W** — increases game speed by one step in the sequence 0×, 0.5×, 1×, 2×, 10× (no wrap-around past 10×).
   - **S** — decreases game speed by one step in the same sequence (no wrap-around past 0×).
   - **A / D** — scroll the view left / right (REQ-UI-SCROLL).
-  - **Q** — context-sensitive. If a build mode is active (builder mode or blueprint placement mode), pressing Q exits it. Otherwise, pressing Q toggles demolish mode: it enters demolish mode if inactive, or exits demolish mode if already active. (See also REQ-UI-DEMOLISH-BUTTON for the equivalent button.)
+  - **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).
@@ -537,9 +553,9 @@ The screen is divided into two columns: a main column (75% width) containing the
 
 - 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, e.g. "Belt: 2 Blocks".
-- 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 Demolish button (REQ-UI-DEMOLISH-BUTTON) is not a building type and has no config-defined tooltip.
+- 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 has no config-defined tooltip.
 - REQ-UI-BUILD-DISABLED: Buttons for buildings the player cannot currently afford are shown as disabled.
-- REQ-UI-DEMOLISH-BUTTON: A dedicated **Demolish** button is shown in the build button grid. Clicking it toggles demolish mode on and off, equivalent to the Q demolish toggle (REQ-UI-HOTKEYS). The button is shown in a visually active/pressed state while demolish mode is active.
+- 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.
 
 ### Blueprint Panel
 
@@ -547,15 +563,15 @@ The screen is divided into two columns: a main column (75% width) containing the
 
 - 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-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 demolish 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.
+- 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.
 
 - 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-MODE: In blueprint placement mode a ghost is rendered for every building in the 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.
+- 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.
 
-- REQ-UI-BLUEPRINT-PLACE: Left-clicking in blueprint placement mode places the 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.
+- 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.
 
 - 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.
 

src/CMakeLists.txt

@@ -117,6 +117,7 @@ target_link_libraries(${TARGET_UI_NAME}
     Qt5::Network
     Qt5::Multimedia
     Qt5::Charts
+    Qt5::Svg
 )
 target_compile_definitions(${TARGET_UI_NAME} PRIVATE TOML_FLOAT_CHARCONV=0)
 

src/lib/config/CMakeLists.txt

@@ -8,6 +8,7 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/StationsConfig.h
     ${CMAKE_CURRENT_SOURCE_DIR}/GameConfig.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ModulesConfig.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/UnlocksConfig.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ConfigLoader.h
     ${CMAKE_CURRENT_SOURCE_DIR}/SurfaceMask.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSerializer.h

src/lib/config/ConfigLoader.cpp

@@ -263,6 +263,7 @@ WorldConfig ConfigLoader::loadWorld(const std::string& path)
 
     cfg.heightTiles                = static_cast<int>(requireInt(tbl["world"]["height_tiles"], file, "world.height_tiles"));
     cfg.refundPercentage           = static_cast<int>(requireInt(tbl["world"]["refund_percentage"], file, "world.refund_percentage"));
+    cfg.deconstructionTimeSeconds  = requireDouble(tbl["world"]["deconstruction_time_seconds"], file, "world.deconstruction_time_seconds");
     cfg.startingBuildingBlocks     = static_cast<int>(requireInt(tbl["world"]["starting_building_blocks"], file, "world.starting_building_blocks"));
     cfg.scrapDespawnSeconds        = requireDouble(tbl["world"]["scrap_despawn_seconds"], file, "world.scrap_despawn_seconds");
     cfg.scrapPerThreat             = requireDouble(tbl["world"]["scrap_per_threat"], file, "world.scrap_per_threat");
@@ -404,18 +405,10 @@ RecipesConfig ConfigLoader::loadRecipes(const std::string& path)
         }
         def.building = *parsedType;
 
-        if (def.building == BuildingType::Assembler)
+        if (def.building == BuildingType::Assembler && mt.contains("unlocked_at_start"))
         {
-            const auto level = mt["unlock_at_station_level"].value<int64_t>();
-            if (level)
-            {
-                def.unlockAtStationLevel = static_cast<int>(*level);
-            }
-            if (mt.contains("unlock_requires"))
-            {
-                def.unlockRequires = requireStringArray(mt["unlock_requires"], file,
-                    elemPath + ".unlock_requires");
-            }
+            def.unlockedAtStart = requireBool(mt["unlocked_at_start"], file,
+                elemPath + ".unlocked_at_start");
         }
 
         // inputs may be omitted (e.g. miner recipes). An empty array is fine.
@@ -454,11 +447,6 @@ ShipsConfig ConfigLoader::loadShips(const std::string& path)
 
         ShipDef def;
         def.id                 = requireString(mt["id"],                 file, elemPath + ".id");
-        def.unlockAtStationLevel = static_cast<int>(requireInt(mt["unlock_at_station_level"], file, elemPath + ".unlock_at_station_level"));
-        if (mt.contains("unlock_requires"))
-        {
-            def.unlockRequires = requireStringArray(mt["unlock_requires"], file, elemPath + ".unlock_requires");
-        }
         def.layout             = requireStringArray(mt["layout"],       file, elemPath + ".layout");
 
         // Schematic
@@ -608,12 +596,6 @@ ModulesConfig ConfigLoader::loadModules(const std::string& path)
 
         ModuleDef def;
         def.id                      = requireString(mt["id"], file, elemPath + ".id");
-        def.unlockAtStationLevel    = static_cast<int>(
-            mt["unlock_at_station_level"].value_or<int64_t>(-1));
-        if (mt.contains("unlock_requires"))
-        {
-            def.unlockRequires = requireStringArray(mt["unlock_requires"], file, elemPath + ".unlock_requires");
-        }
         def.surfaceMask             = requireStringArray(mt["surface_mask"], file, elemPath + ".surface_mask");
         def.productionTimeSeconds = requireDouble(
             mt["production_time_seconds"], file, elemPath + ".production_time_seconds");
@@ -731,62 +713,141 @@ ModulesConfig ConfigLoader::loadModules(const std::string& path)
     return cfg;
 }
 
+UnlocksConfig ConfigLoader::loadUnlocks(const std::string& path)
+{
+    const std::string file = "unlocks.toml";
+    toml::table tbl = parseFile(path, file);
+
+    UnlocksConfig cfg;
+    if (!tbl.contains("unlock"))
+    {
+        return cfg;
+    }
+
+    const toml::array& arr = requireArray(tbl["unlock"], file, "unlock");
+
+    for (std::size_t i = 0; i < arr.size(); ++i)
+    {
+        const std::string elemPath = "unlock[" + std::to_string(i) + "]";
+        const toml::table* ut = arr[i].as_table();
+        if (ut == nullptr)
+        {
+            throw makeError(file, elemPath, "not a table");
+        }
+        toml::table& mt = const_cast<toml::table&>(*ut);
+
+        UnlockGroupDef def;
+        def.id           = requireString(mt["id"], file, elemPath + ".id");
+        def.stationLevel = static_cast<int>(
+            requireInt(mt["station_level"], file, elemPath + ".station_level"));
+        if (mt.contains("requires"))
+        {
+            def.requiredGroupIds = requireStringArray(mt["requires"], file, elemPath + ".requires");
+        }
+        if (mt.contains("ships"))
+        {
+            def.ships = requireStringArray(mt["ships"], file, elemPath + ".ships");
+        }
+        if (mt.contains("modules"))
+        {
+            def.modules = requireStringArray(mt["modules"], file, elemPath + ".modules");
+        }
+        if (mt.contains("buildings"))
+        {
+            def.buildings = requireStringArray(mt["buildings"], file, elemPath + ".buildings");
+        }
+        if (mt.contains("recipes"))
+        {
+            def.recipes = requireStringArray(mt["recipes"], file, elemPath + ".recipes");
+        }
+
+        cfg.groups.push_back(std::move(def));
+    }
+
+    return cfg;
+}
+
 namespace
 {
 
-// Throws if any id in requiredIds is not a valid explicitly-unlockable schematic.
-void checkUnlockRequires(const std::vector<std::string>& requiredIds,
-                         const std::unordered_set<std::string>& schematicIds,
-                         const std::string& file,
-                         const std::string& path)
+// Validates unlocks.toml against the rest of the config (REQ-LOCK-EXPLICIT,
+// REQ-LOCK-PREREQ): each granted id resolves to the right kind of definition
+// (recipe grants must name assembler recipes), each grantable id is granted by
+// at most one group, group ids are unique, every group grants at least one
+// item, and every `requires` id names a defined group.
+void validateUnlocks(const GameConfig& cfg)
 {
-    for (const std::string& requiredId : requiredIds)
-    {
-        if (schematicIds.count(requiredId) == 0)
-        {
-            throw makeError(file, path,
-                "references unknown schematic '" + requiredId + "'");
-        }
-    }
-}
+    const std::string file = "unlocks.toml";
 
-// Validates that every id listed in an `unlock_requires` (REQ-LOCK-PREREQ)
-// resolves to an explicitly-unlockable schematic: a ship, a module, or an
-// assembler recipe that carries `unlock_at_station_level` (a recipe schematic,
-// per REQ-LOCK-EXPLICIT). An unresolved id is a config error surfaced at load.
-void validateUnlockRequires(const GameConfig& cfg)
-{
-    std::unordered_set<std::string> schematicIds;
-    for (const ShipDef& def : cfg.ships.ships)
-    {
-        schematicIds.insert(def.id);
-    }
-    for (const ModuleDef& def : cfg.modules.modules)
-    {
-        schematicIds.insert(def.id);
-    }
+    std::unordered_set<std::string> shipIds;
+    for (const ShipDef& def : cfg.ships.ships) { shipIds.insert(def.id); }
+    std::unordered_set<std::string> moduleIds;
+    for (const ModuleDef& def : cfg.modules.modules) { moduleIds.insert(def.id); }
+    std::unordered_set<std::string> buildingIds;
+    for (const BuildingDef& def : cfg.buildings.buildings) { buildingIds.insert(def.id); }
+    std::unordered_set<std::string> assemblerRecipeIds;
     for (const RecipeDef& def : cfg.recipes.recipes)
     {
-        if (def.building == BuildingType::Assembler && def.unlockAtStationLevel.has_value())
-        {
-            schematicIds.insert(def.id);
-        }
+        if (def.building == BuildingType::Assembler) { assemblerRecipeIds.insert(def.id); }
     }
 
-    for (const ShipDef& def : cfg.ships.ships)
+    std::unordered_set<std::string> groupIds;
+    std::unordered_set<std::string> grantedShipIds;
+    std::unordered_set<std::string> grantedModuleIds;
+    std::unordered_set<std::string> grantedBuildingIds;
+    std::unordered_set<std::string> grantedRecipeIds;
+
+    const auto checkGrants = [&](const std::vector<std::string>& ids,
+                                 const std::unordered_set<std::string>& valid,
+                                 std::unordered_set<std::string>& granted,
+                                 const std::string& kind,
+                                 const std::string& gPath)
     {
-        checkUnlockRequires(def.unlockRequires, schematicIds, "ships.toml",
-                            "ship '" + def.id + "'.unlock_requires");
+        for (const std::string& id : ids)
+        {
+            if (valid.count(id) == 0)
+            {
+                throw makeError(file, gPath, "grants unknown " + kind + " '" + id + "'");
+            }
+            if (!granted.insert(id).second)
+            {
+                throw makeError(file, gPath,
+                    "grants " + kind + " '" + id + "' which is already granted by another unlock group");
+            }
+        }
+    };
+
+    for (const UnlockGroupDef& group : cfg.unlocks.groups)
+    {
+        const std::string gPath = "unlock '" + group.id + "'";
+        if (!groupIds.insert(group.id).second)
+        {
+            throw makeError(file, gPath, "duplicate unlock group id");
+        }
+
+        if (group.ships.empty() && group.modules.empty()
+            && group.buildings.empty() && group.recipes.empty())
+        {
+            throw makeError(file, gPath, "grants no items (must grant at least one)");
+        }
+
+        checkGrants(group.ships,     shipIds,            grantedShipIds,     "ship",             gPath);
+        checkGrants(group.modules,   moduleIds,          grantedModuleIds,   "module",           gPath);
+        checkGrants(group.buildings, buildingIds,        grantedBuildingIds, "building",         gPath);
+        checkGrants(group.recipes,   assemblerRecipeIds, grantedRecipeIds,   "assembler recipe", gPath);
     }
-    for (const ModuleDef& def : cfg.modules.modules)
+
+    // requires must reference defined group ids (checked once all group ids known).
+    for (const UnlockGroupDef& group : cfg.unlocks.groups)
     {
-        checkUnlockRequires(def.unlockRequires, schematicIds, "modules.toml",
-                            "module '" + def.id + "'.unlock_requires");
-    }
-    for (const RecipeDef& def : cfg.recipes.recipes)
-    {
-        checkUnlockRequires(def.unlockRequires, schematicIds, "recipes.toml",
-                            "recipe '" + def.id + "'.unlock_requires");
+        for (const std::string& req : group.requiredGroupIds)
+        {
+            if (groupIds.count(req) == 0)
+            {
+                throw makeError(file, "unlock '" + group.id + "'.requires",
+                    "references unknown unlock group '" + req + "'");
+            }
+        }
     }
 }
 
@@ -801,7 +862,8 @@ GameConfig ConfigLoader::loadFromDirectory(const std::string& configDir)
     cfg.ships     = loadShips(configDir + "/ships.toml");
     cfg.stations  = loadStations(configDir + "/stations.toml");
     cfg.modules   = loadModules(configDir + "/modules.toml");
-    validateUnlockRequires(cfg);
+    cfg.unlocks   = loadUnlocks(configDir + "/unlocks.toml");
+    validateUnlocks(cfg);
     cfg.threatCosts = computeThreatCostTable(cfg);
     return cfg;
 }

src/lib/config/ConfigLoader.h

@@ -22,4 +22,5 @@ public:
     static ShipsConfig loadShips(const std::string& path);
     static StationsConfig loadStations(const std::string& path);
     static ModulesConfig loadModules(const std::string& path);
+    static UnlocksConfig loadUnlocks(const std::string& path);
 };

src/lib/config/GameConfig.h

@@ -6,6 +6,7 @@
 #include "ShipsConfig.h"
 #include "StationsConfig.h"
 #include "ModulesConfig.h"
+#include "UnlocksConfig.h"
 #include "ThreatCostCalculator.h"
 
 // Aggregate of all simulation config files. Loaded at startup and reloaded
@@ -18,5 +19,6 @@ struct GameConfig
     ShipsConfig ships;
     StationsConfig stations;
     ModulesConfig modules;
+    UnlocksConfig unlocks;
     ThreatCostTable threatCosts;
 };

src/lib/config/ModulesConfig.h

@@ -40,10 +40,6 @@ struct ModuleRepairCapability
 struct ModuleDef
 {
     std::string id;
-    int unlockAtStationLevel;
-    // Prerequisite schematic ids that must be explicitly unlocked before this
-    // schematic can enter the drop pool (REQ-LOCK-PREREQ). Empty = none.
-    std::vector<std::string> unlockRequires;
     std::vector<std::string> surfaceMask;
     std::vector<RecipeIngredient> materials;
     double productionTimeSeconds;

src/lib/config/RecipesConfig.h

@@ -32,14 +32,12 @@ struct RecipeDef
     std::vector<RecipeIngredient> inputs;
     std::vector<RecipeOutput> outputs;
     double durationSeconds;
-    // Assembler only. nullopt = implicit-only locking. -1 = explicitly unlocked
-    // at game start. >= 0 = locked; schematic enters drop pool at that station
-    // level once the output item is implicitly unlocked (REQ-LOCK-EXPLICIT).
-    std::optional<int> unlockAtStationLevel;
-    // Assembler recipe schematics only. Prerequisite schematic ids that must be
-    // explicitly unlocked before this schematic can enter the drop pool
-    // (REQ-LOCK-PREREQ). Empty = none.
-    std::vector<std::string> unlockRequires;
+    // 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.
+    // Otherwise an assembler recipe is either explicitly gated (granted by an
+    // unlock group, REQ-LOCK-EXPLICIT) or implicitly gated via the item graph.
+    bool unlockedAtStart = false;
 };
 
 struct RecipesConfig

src/lib/config/ShipsConfig.h

@@ -35,10 +35,6 @@ struct ShipSensor
 struct ShipDef
 {
     std::string id;
-    int unlockAtStationLevel;
-    // Prerequisite schematic ids that must be explicitly unlocked before this
-    // schematic can enter the drop pool (REQ-LOCK-PREREQ). Empty = none.
-    std::vector<std::string> unlockRequires;
     std::vector<std::string> layout;
 
     ShipSchematic schematic;

src/lib/config/UnlocksConfig.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+// A single [[unlock]] entry from unlocks.toml — an unlock group, the unit of
+// loot awarded by defence station drops (REQ-DEF-SCHEMATIC-DROP,
+// REQ-LOCK-EXPLICIT). Awarding a group unlocks all of its granted members at
+// once. Anything not granted by any group is available from game start.
+struct UnlockGroupDef
+{
+    std::string id;                              // Unique unlock-group id.
+    int stationLevel;                            // Min destroyed station level to become eligible.
+    std::vector<std::string> requiredGroupIds;   // Prerequisite unlock-group ids (REQ-LOCK-PREREQ).
+
+    // Granted ids by kind (each defaults to empty; a group grants >= 1 item).
+    std::vector<std::string> ships;
+    std::vector<std::string> modules;
+    std::vector<std::string> buildings;
+    std::vector<std::string> recipes;            // Assembler recipe ids only.
+};
+
+struct UnlocksConfig
+{
+    std::vector<UnlockGroupDef> groups;
+};

src/lib/config/WorldConfig.h

@@ -67,7 +67,8 @@ struct WorldScroll
 struct WorldConfig
 {
     int heightTiles;                    // REQ-GW-HEIGHT
-    int refundPercentage;               // REQ-BLD-DEMOLISH
+    int refundPercentage;               // REQ-BLD-DECONSTRUCT
+    double deconstructionTimeSeconds;   // REQ-BLD-DECON-QUEUE
     int startingBuildingBlocks;         // REQ-HQ-STARTING-BLOCKS
     double scrapDespawnSeconds;         // REQ-RES-SCRAP-DROP
     double scrapPerThreat;              // REQ-RES-SCRAP-DROP, REQ-THREAT-SCRAP (scrap dropped per unit threat)

src/lib/core/SchematicChoiceOption.h

@@ -3,23 +3,43 @@
 #include <string>
 #include <vector>
 
+// The kind of a single granted schematic within an unlock option.
 enum class SchematicType
 {
     Ship,
     Module,
-    Recipe,
-    Artifact
+    Building,
+    Recipe
+};
+
+// One item granted by an unlock group (REQ-LOCK-EXPLICIT), shown in the
+// schematic choice dialog's granted-items list.
+struct GrantedSchematic
+{
+    SchematicType type;
+    std::string id;
+    std::string displayName;
 };
 
 // One option presented to the player in the schematic choice dialog
 // (REQ-DEF-SCHEMATIC-DROP). Built by the simulation when enemy stations are
-// destroyed; the UI reads these to populate the dialog.
+// destroyed; the UI reads these to populate the dialog. A non-artifact option
+// represents one unlock group; selecting it awards the whole group.
 struct SchematicChoiceOption
 {
-    std::string schematicId;
-    SchematicType type;
+    bool isArtifact = false;
+
+    // Unlock group id (empty for the artifact option).
+    std::string unlockGroupId;
+
+    // Display name shown as the option's title: the unlock group's derived name,
+    // or "Artifact" for the artifact option.
     std::string displayName;
 
+    // The ships, modules, buildings, and assembler recipes this group grants
+    // (empty for the artifact option).
+    std::vector<GrantedSchematic> grantedItems;
+
     // Ids of miner/assembler recipes that would newly become implicitly
     // unlocked (REQ-LOCK-IMPLICIT) if this option is selected. Sorted
     // alphabetically by display name; empty if none.

src/lib/eventsystem/event/CMakeLists.txt

@@ -12,14 +12,15 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/GameOverEvent.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}/EscapeMenuRequestedEvent.h
-	${CMAKE_CURRENT_SOURCE_DIR}/DemolishModeChangedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/DeconstructModeChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BuildingTypeSelectedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BuildHotkeyPressedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/ExitBuilderModeRequestedEvent.h
-	${CMAKE_CURRENT_SOURCE_DIR}/DemolishModeToggleRequestedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/DeconstructModeToggleRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BlueprintPlacementRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/ExitBlueprintModeRequestedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/TemporaryBlueprintRequestedEvent.h

src/lib/eventsystem/event/DeconstructModeChangedEvent.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "Event.h"
+
+class DeconstructModeChangedEvent : public Event
+{
+public:
+    explicit DeconstructModeChangedEvent(bool active) : active(active) {}
+    const bool active;
+};

src/lib/eventsystem/event/DeconstructModeToggleRequestedEvent.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include "Event.h"
+
+class DeconstructModeToggleRequestedEvent : public Event
+{
+};

src/lib/eventsystem/event/DemolishModeChangedEvent.h

@@ -1,10 +0,0 @@
-#pragma once
-
-#include "Event.h"
-
-class DemolishModeChangedEvent : public Event
-{
-public:
-    explicit DemolishModeChangedEvent(bool active) : active(active) {}
-    const bool active;
-};

src/lib/eventsystem/event/DemolishModeToggleRequestedEvent.h

@@ -1,7 +0,0 @@
-#pragma once
-
-#include "Event.h"
-
-class DemolishModeToggleRequestedEvent : public Event
-{
-};

src/lib/eventsystem/event/UnlockedBuildingsChangedEvent.h

@@ -0,0 +1,13 @@
+#ifndef UNLOCKED_BUILDINGS_CHANGED_EVENT_H
+#define UNLOCKED_BUILDINGS_CHANGED_EVENT_H
+
+#include "Event.h"
+
+// 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.
+class UnlockedBuildingsChangedEvent : public Event
+{
+};
+
+#endif   // UNLOCKED_BUILDINGS_CHANGED_EVENT_H

src/lib/sim/BeltSystem.h

@@ -52,7 +52,7 @@ public:
     // tile are held and routed to one of the two outputs.
     void placeSplitter(QPoint tile, Rotation outputA, Rotation outputB);
 
-    // Remove a belt or splitter tile (on demolish).  Items are discarded.
+    // Remove a belt or splitter tile (on deconstruct).  Items are discarded.
     void removeTile(QPoint tile);
 
     // -- Splitter filter configuration (REQ-BLD-SPLITTER) -------------------

src/lib/sim/Building.h

@@ -129,5 +129,10 @@ struct Building
 
     // Module layout for shipyards (REQ-MOD-LAYOUT).
     std::optional<ShipLayoutConfig> shipLayout;
+
+    // True while this building sits in the deconstruction queue (REQ-BLD-DECON-QUEUE).
+    // A queued building stops operating immediately (all tick loops skip it) but keeps
+    // occupying its tiles until its deconstruction completes.
+    bool queuedForDeconstruction = false;
 };
 

src/lib/sim/BuildingSystem.cpp

@@ -21,6 +21,17 @@ bool isAutoRecipeBuildingType(BuildingType type)
         || type == BuildingType::ReprocessingPlant;
 }
 
+// Belts, splitters, and tunnel ends keep their runtime data in the belt subsystem
+// rather than in the Building instance, so placing/removing them must register or
+// unregister a tile with BeltSystem.
+bool isBeltSubsystemType(BuildingType type)
+{
+    return type == BuildingType::Belt
+        || type == BuildingType::Splitter
+        || type == BuildingType::TunnelEntry
+        || type == BuildingType::TunnelExit;
+}
+
 // The building body tile that owns an output port, given the port's outside tile
 // (port.tile) and its facing direction. The virtual output belt occupies this tile
 // and flows toward port.tile (REQ-MAT-OUTPUT-EMERGE).
@@ -486,12 +497,13 @@ bool BuildingSystem::isPlacementValid(BuildingType type, QPoint anchor,
 }
 
 // ---------------------------------------------------------------------------
-// Demolish
+// Deconstruct
 // ---------------------------------------------------------------------------
 
-int BuildingSystem::demolish(BuildingId id)
+int BuildingSystem::deconstruct(BuildingId id, Tick currentTick)
 {
-    // Construction queue?
+    // Construction site? Removed instantly with the full refund; never queued
+    // for deconstruction (REQ-BLD-DECONSTRUCT).
     for (std::deque<ConstructionSite>::iterator it = m_constructionQueue.begin();
          it != m_constructionQueue.end();
          ++it)
@@ -512,35 +524,60 @@ int BuildingSystem::demolish(BuildingId id)
         }
     }
 
-    // Operational building?
-    for (std::vector<Building>::iterator it = m_buildings.begin();
-         it != m_buildings.end();
-         ++it)
+    // Operational building? Append it to the deconstruction queue rather than
+    // removing it now; the partial refund is credited on completion in
+    // tickDeconstruction (REQ-BLD-DECON-QUEUE).
+    for (Building& building : m_buildings)
     {
-        if (it->id == id)
+        if (building.id != id) { continue; }
+        if (building.queuedForDeconstruction) { return 0; }  // already queued
+
+        building.queuedForDeconstruction = true;
+
+        DeconstructionEntry entry;
+        entry.id = id;
+
+        // A queued belt/tunnel/splitter stops transporting at once: capture a
+        // splitter's filters (so an un-queue can restore them), then unregister
+        // its tile, discarding items on it and re-pairing tunnels as if it were
+        // gone (REQ-BLD-TUNNEL-PAIR).
+        if (building.type == BuildingType::Splitter)
         {
-            if (it->type == BuildingType::Belt || it->type == BuildingType::Splitter
-                || it->type == BuildingType::TunnelEntry || it->type == BuildingType::TunnelExit)
+            if (const std::optional<BeltSystem::SplitterInfo> info =
+                    m_belts.getSplitterInfo(building.anchor))
             {
-                m_belts.removeTile(it->anchor);
+                entry.splitterFilterA = info->filterA;
+                entry.splitterFilterB = info->filterB;
             }
-            const BuildingDef* def = findBuildingDef(it->type);
-            for (const QPoint& cell : it->bodyCells)
-            {
-                m_tileOccupancy.erase({cell.x(), cell.y()});
-            }
-            m_buildings.erase(it);
-            if (def)
-            {
-                return def->cost * m_config.world.refundPercentage / 100;
-            }
-            return 0;
         }
+        if (isBeltSubsystemType(building.type))
+        {
+            m_belts.removeTile(building.anchor);
+        }
+
+        const bool wasEmpty = m_deconstructionQueue.empty();
+        m_deconstructionQueue.push_back(std::move(entry));
+        if (wasEmpty)
+        {
+            startFrontDeconstruction(currentTick);
+        }
+        return 0;
     }
 
     return 0;
 }
 
+void BuildingSystem::startFrontDeconstruction(Tick currentTick)
+{
+    if (m_deconstructionQueue.empty()) { return; }
+    DeconstructionEntry& front = m_deconstructionQueue.front();
+    if (front.completesAt == 0)
+    {
+        front.completesAt =
+            currentTick + secondsToTicks(m_config.world.deconstructionTimeSeconds);
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Set recipe
 // ---------------------------------------------------------------------------
@@ -780,31 +817,9 @@ void BuildingSystem::tickConstruction(Tick currentTick)
         }
     }
 
-    // Register with BeltSystem before the move (mask stays valid).
-    if (front.type == BuildingType::Belt)
-    {
-        m_belts.placeBelt(front.anchor, front.rotation);
-    }
-    else if (front.type == BuildingType::Splitter)
-    {
-        assert(mask.outputPorts.size() >= 2);
-        m_belts.placeSplitter(front.anchor,
-                              mask.outputPorts[0].direction,
-                              mask.outputPorts[1].direction);
-        // Carry over any filters configured while under construction
-        // (REQ-BLD-SITE-CONFIG).
-        m_belts.setSplitterFilters(front.anchor,
-                                   front.splitterFilterA,
-                                   front.splitterFilterB);
-    }
-    else if (front.type == BuildingType::TunnelEntry)
-    {
-        m_belts.placeTunnelEntry(front.anchor, front.rotation, m_config.world.tunnelMaxDistance_tiles);
-    }
-    else if (front.type == BuildingType::TunnelExit)
-    {
-        m_belts.placeTunnelExit(front.anchor, front.rotation);
-    }
+    // Register with BeltSystem before the move (mask/building stays valid). Any
+    // filters configured while under construction carry over (REQ-BLD-SITE-CONFIG).
+    reregisterBeltTile(building, front.splitterFilterA, front.splitterFilterB);
 
     m_buildings.push_back(std::move(building));
 
@@ -822,6 +837,114 @@ void BuildingSystem::tickConstruction(Tick currentTick)
     }
 }
 
+void BuildingSystem::reregisterBeltTile(const Building& building,
+                                        const std::vector<ItemType>& splitterFilterA,
+                                        const std::vector<ItemType>& splitterFilterB)
+{
+    switch (building.type)
+    {
+        case BuildingType::Belt:
+            m_belts.placeBelt(building.anchor, building.rotation);
+            break;
+        case BuildingType::Splitter:
+            assert(building.outputPorts.size() >= 2);
+            m_belts.placeSplitter(building.anchor,
+                                  building.outputPorts[0].direction,
+                                  building.outputPorts[1].direction);
+            m_belts.setSplitterFilters(building.anchor, splitterFilterA, splitterFilterB);
+            break;
+        case BuildingType::TunnelEntry:
+            m_belts.placeTunnelEntry(building.anchor, building.rotation,
+                                     m_config.world.tunnelMaxDistance_tiles);
+            break;
+        case BuildingType::TunnelExit:
+            m_belts.placeTunnelExit(building.anchor, building.rotation);
+            break;
+        default:
+            break;
+    }
+}
+
+void BuildingSystem::tickDeconstruction(Tick currentTick)
+{
+    TRACE();
+    if (m_deconstructionQueue.empty())
+    {
+        return;
+    }
+
+    DeconstructionEntry& front = m_deconstructionQueue.front();
+
+    // Guard: if the front entry's timer was never started, start it now.
+    if (front.completesAt == 0)
+    {
+        startFrontDeconstruction(currentTick);
+        return;
+    }
+
+    if (currentTick < front.completesAt)
+    {
+        return;
+    }
+
+    // Remove the building from the world and credit its refund (REQ-BLD-DECONSTRUCT).
+    // Belt/tunnel/splitter tiles were already unregistered when the building was
+    // queued (see deconstruct), so only tile occupancy and the record remain.
+    for (std::vector<Building>::iterator it = m_buildings.begin();
+         it != m_buildings.end();
+         ++it)
+    {
+        if (it->id != front.id) { continue; }
+
+        const BuildingDef* def = findBuildingDef(it->type);
+        for (const QPoint& cell : it->bodyCells)
+        {
+            m_tileOccupancy.erase({cell.x(), cell.y()});
+        }
+        m_buildings.erase(it);
+        if (def)
+        {
+            m_addBuildingBlocks(def->cost * m_config.world.refundPercentage / 100);
+        }
+        break;
+    }
+
+    m_deconstructionQueue.pop_front();
+
+    // Start the next queued deconstruction, if any.
+    startFrontDeconstruction(currentTick);
+}
+
+void BuildingSystem::cancelDeconstruction(BuildingId id)
+{
+    for (std::deque<DeconstructionEntry>::iterator it = m_deconstructionQueue.begin();
+         it != m_deconstructionQueue.end();
+         ++it)
+    {
+        if (it->id != id) { continue; }
+
+        // Resume operation: clear the flag and re-register belt/tunnel/splitter
+        // tiles that were unregistered at enqueue (which re-pairs tunnels,
+        // REQ-BLD-TUNNEL-PAIR). Deconstruction progress is discarded; no refund.
+        if (Building* building = findBuildingMutable(id))
+        {
+            building->queuedForDeconstruction = false;
+            reregisterBeltTile(*building, it->splitterFilterA, it->splitterFilterB);
+        }
+
+        m_deconstructionQueue.erase(it);
+        // If the running front was removed, the new front (completesAt == 0) has
+        // its timer started by the next tickDeconstruction guard.
+        return;
+    }
+}
+
+bool BuildingSystem::isQueuedForDeconstruction(BuildingId id) const
+{
+    const Building* building = findBuilding(id);
+    return building && building->queuedForDeconstruction;
+}
+
 void BuildingSystem::tickBeltPull()
 {
 	TRACE();
@@ -831,6 +954,9 @@ void BuildingSystem::tickBeltPull()
 
     for (Building& building : m_buildings)
     {
+        // A building queued for deconstruction stops operating (REQ-BLD-DECON-QUEUE).
+        if (building.queuedForDeconstruction) { continue; }
+
         const bool isHq = (building.type == BuildingType::Hq);
 
         // 1. Advance every input belt and deliver arrivals (progress >= 0.5) into
@@ -922,6 +1048,10 @@ bool BuildingSystem::tryDirectCoupleDeposit(BuildingId producerId,
     {
         return false;  // an unbuilt construction site, or not an operational building
     }
+    if (consumer->queuedForDeconstruction)
+    {
+        return false;  // queued for deconstruction: stopped operating (REQ-BLD-DECON-QUEUE)
+    }
 
     // The coupling is the consumer input port meeting this output port: same flow
     // direction, feeding the producer's output-port tile (REQ-MAT-DIRECT-COUPLE).
@@ -943,6 +1073,9 @@ void BuildingSystem::tickProduction(Tick currentTick)
 	TRACE();
     for (Building& building : m_buildings)
     {
+        // A building queued for deconstruction stops operating (REQ-BLD-DECON-QUEUE).
+        if (building.queuedForDeconstruction) { continue; }
+
         // Skip types without a recipe-based production loop.
         if (building.type == BuildingType::Belt     ||
             building.type == BuildingType::Splitter  ||
@@ -1043,6 +1176,9 @@ void BuildingSystem::tickShipyardProduction(Tick currentTick)
 	TRACE();
     for (Building& building : m_buildings)
     {
+        // A building queued for deconstruction stops operating (REQ-BLD-DECON-QUEUE).
+        if (building.queuedForDeconstruction) { continue; }
+
         if (building.type != BuildingType::Shipyard)
         {
             continue;
@@ -1140,6 +1276,9 @@ void BuildingSystem::tickOutputBelts()
 
     for (Building& building : m_buildings)
     {
+        // A building queued for deconstruction stops operating (REQ-BLD-DECON-QUEUE).
+        if (building.queuedForDeconstruction) { continue; }
+
         for (std::size_t p = 0; p < building.outputPorts.size(); ++p)
         {
             const Port& port = building.outputPorts[p];
@@ -1493,7 +1632,7 @@ std::optional<BuildingId> BuildingSystem::findRotateInPlaceTarget(
     BuildingType type, QPoint anchor, Rotation rot) const
 {
     // Tunnel Entries and Tunnel Exits cannot be rotated in place; re-orienting a
-    // tunnel requires demolishing and re-placing it (REQ-BLD-ROTATE-IN-PLACE).
+    // tunnel requires deconstructing and re-placing it (REQ-BLD-ROTATE-IN-PLACE).
     if (type == BuildingType::TunnelEntry || type == BuildingType::TunnelExit)
     {
         return std::nullopt;
@@ -1647,6 +1786,10 @@ bool BuildingSystem::deliverScrapToSalvageBay(BuildingId bayId)
     {
         return false;
     }
+    if (bay->queuedForDeconstruction)
+    {
+        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)
@@ -1820,6 +1963,7 @@ void BuildingSystem::appendChecksum(Hasher& hasher) const
             appendItems(hasher, b.production->chosenOutputs);
         }
         hasher.append(b.shipLayout.has_value());
+        hasher.append(b.queuedForDeconstruction);
     }
 
     hasher.append(m_constructionQueue.size());
@@ -1840,6 +1984,17 @@ void BuildingSystem::appendChecksum(Hasher& hasher) const
         for (const ItemType& type : s.splitterFilterB) { hasher.append(type.id); }
     }
 
+    hasher.append(m_deconstructionQueue.size());
+    for (const DeconstructionEntry& e : m_deconstructionQueue)
+    {
+        hasher.append(e.id);
+        hasher.append(e.completesAt);
+        hasher.append(e.splitterFilterA.size());
+        for (const ItemType& type : e.splitterFilterA) { hasher.append(type.id); }
+        hasher.append(e.splitterFilterB.size());
+        for (const ItemType& type : e.splitterFilterB) { hasher.append(type.id); }
+    }
+
     // std::map iterates in sorted key order.
     hasher.append(m_tileOccupancy.size());
     for (const std::pair<const std::pair<int, int>, BuildingId>& entry : m_tileOccupancy)

src/lib/sim/BuildingSystem.h

@@ -54,7 +54,7 @@ public:
                    std::function<bool(const std::string&)> isItemUnlocked,
                    std::mt19937& rng);
 
-    // -- Placement / demolish ------------------------------------------------
+    // -- Placement / deconstruct ------------------------------------------------
     // Returns the new entity id, or nullopt if the placement falls outside the
     // world bounds (vertical extent and asteroid left edge).  Belt and Splitter
     // register with BeltSystem directly; other types enter the construction
@@ -77,10 +77,22 @@ public:
     // Defaults to world.regions.asteroid_width_tiles at construction.
     void setAsteroidWidth_tiles(int widthTiles) { m_asteroidWidth_tiles = widthTiles; }
 
-    // Remove a building or construction site by id.  Returns the refund in
-    // building blocks (floor(cost * refundPercentage / 100)).  Returns 0 for
-    // unknown ids.
-    int demolish(BuildingId id);
+    // Mark a building or construction site for demolition (REQ-BLD-DECONSTRUCT).
+    // A construction site is removed instantly and the full cost is returned.
+    // A fully-built building is instead appended to the deconstruction queue
+    // (REQ-BLD-DECON-QUEUE) and stops operating at once; its (partial) refund is
+    // credited later, on completion in tickDeconstruction, so this returns 0 for
+    // it. Returns 0 for unknown ids and for a building already queued.
+    int deconstruct(BuildingId id, Tick currentTick);
+
+    // Take a building back out of the deconstruction queue before it is removed
+    // (REQ-BLD-DECON-QUEUE). Clears its queued flag and resumes operation
+    // (re-registering belt/tunnel/splitter tiles); discards deconstruction
+    // progress and credits no refund. No-op if the id is not queued.
+    void cancelDeconstruction(BuildingId id);
+
+    // True if the building is currently in the deconstruction queue.
+    bool isQueuedForDeconstruction(BuildingId id) const;
 
     // Set the recipe (or schematic id for shipyard) on a building or queued
     // construction site.  Clears both buffers on an operational building.
@@ -104,6 +116,10 @@ public:
 
     // -- Tick hooks (called from Simulation::tick in the documented order) ---
     void tickConstruction(Tick currentTick);
+    // Advances the deconstruction queue (REQ-BLD-DECON-QUEUE): one building at a
+    // time, in parallel with tickConstruction. Removes the front building and
+    // credits its refund when its timer elapses.
+    void tickDeconstruction(Tick currentTick);
     void tickBeltPull();
     void tickProduction(Tick currentTick);
     void tickShipyardProduction(Tick currentTick);
@@ -205,6 +221,17 @@ public:
     void appendChecksum(Hasher& hasher) const;
 
 private:
+    // Starts the front deconstruction-queue entry's timer if not yet started
+    // (mirrors how tickConstruction starts a queued construction site).
+    void                 startFrontDeconstruction(Tick currentTick);
+
+    // Registers a belt/splitter/tunnel building's tile with the belt subsystem
+    // (on construction completion, or when un-queuing a deconstruction). No-op for
+    // non-belt-subsystem types. Splitter filters are (re)applied after placement.
+    void                 reregisterBeltTile(const Building& building,
+                                            const std::vector<ItemType>& splitterFilterA,
+                                            const std::vector<ItemType>& splitterFilterB);
+
     Building*            findBuildingMutable(BuildingId id);
     // 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
@@ -273,6 +300,19 @@ private:
     std::vector<Building>           m_buildings;
     std::deque<ConstructionSite>    m_constructionQueue;
 
+    // One pending demolition of a fully-built building (REQ-BLD-DECON-QUEUE).
+    // completesAt == 0 means "queued but its timer has not started yet"
+    // (mirrors ConstructionSite). For a Splitter, the filters it had are captured
+    // here so cancelDeconstruction can restore them on re-registration.
+    struct DeconstructionEntry
+    {
+        BuildingId            id          = kInvalidBuildingId;
+        Tick                  completesAt = 0;
+        std::vector<ItemType> splitterFilterA;
+        std::vector<ItemType> splitterFilterB;
+    };
+    std::deque<DeconstructionEntry> m_deconstructionQueue;
+
     // Maps every occupied body-cell coordinate to the entity that owns it.
     std::map<std::pair<int, int>, BuildingId> m_tileOccupancy;
 };

src/lib/sim/Command.h

@@ -27,7 +27,8 @@ class GameConfig;
 enum class CommandKind
 {
     PlaceBuilding,
-    Demolish,
+    Deconstruct,
+    CancelDeconstruction,
     RotateInPlace,
     SetRecipe,
     SetShipLayout,
@@ -72,9 +73,19 @@ struct PlaceBuildingCommand : Command
     std::vector<ItemType>           splitterFilterB;
 };
 
-struct DemolishCommand : Command
+// Marks a building for demolition: a construction site is removed instantly, a
+// built building is queued for deconstruction (REQ-BLD-DECONSTRUCT, REQ-BLD-DECON-QUEUE).
+struct DeconstructCommand : Command
 {
-    DemolishCommand() : Command(CommandKind::Demolish) {}
+    DeconstructCommand() : Command(CommandKind::Deconstruct) {}
+    std::optional<BuildingId> id;
+};
+
+// Takes a building back out of the deconstruction queue (REQ-BLD-DECONSTRUCT-CLICK,
+// REQ-BLD-DECONSTRUCT-BOX). No-op if the id is not currently queued.
+struct CancelDeconstructionCommand : Command
+{
+    CancelDeconstructionCommand() : Command(CommandKind::CancelDeconstruction) {}
     std::optional<BuildingId> id;
 };
 

src/lib/sim/CommandSerializer.cpp

@@ -128,8 +128,12 @@ std::string serializeCommand(const Command& command)
         }
         break;
     }
-    case CommandKind::Demolish:
-        out << "demolish " << static_cast<const DemolishCommand&>(command).id.value();
+    case CommandKind::Deconstruct:
+        out << "deconstruct " << static_cast<const DeconstructCommand&>(command).id.value();
+        break;
+    case CommandKind::CancelDeconstruction:
+        out << "cancel_deconstruct "
+            << static_cast<const CancelDeconstructionCommand&>(command).id.value();
         break;
     case CommandKind::RotateInPlace:
     {
@@ -239,9 +243,18 @@ std::shared_ptr<Command> parseCommand(const std::string& tokens)
         }
         return c;
     }
-    if (verb == "demolish")
+    if (verb == "deconstruct")
     {
-        std::shared_ptr<DemolishCommand> c = std::make_shared<DemolishCommand>();
+        std::shared_ptr<DeconstructCommand> c = std::make_shared<DeconstructCommand>();
+        BuildingId id = 0;
+        if (!(in >> id)) { return nullptr; }
+        c->id = id;
+        return c;
+    }
+    if (verb == "cancel_deconstruct")
+    {
+        std::shared_ptr<CancelDeconstructionCommand> c =
+            std::make_shared<CancelDeconstructionCommand>();
         BuildingId id = 0;
         if (!(in >> id)) { return nullptr; }
         c->id = id;

src/lib/sim/Simulation.cpp

@@ -75,34 +75,7 @@ Simulation::Simulation(GameConfig config, unsigned int seed)
     m_waveSystem     = std::make_unique<WaveSystem>(m_config, m_rng);
     m_combatSystem   = std::make_unique<CombatSystem>(m_config);
 
-    // Initialize ship schematic unlock state.
-    for (const ShipDef& def : m_config.ships.ships)
-    {
-        SchematicState state;
-        state.unlocked = (def.unlockAtStationLevel == -1);
-        m_schematicLevels[def.id] = state;
-    }
-
-    // Initialize module schematic unlock state.
-    for (const ModuleDef& def : m_config.modules.modules)
-    {
-        SchematicState state;
-        state.unlocked = (def.unlockAtStationLevel == -1);
-        m_moduleSchematicLevels[def.id] = state;
-    }
-
-    // Initialize assembler recipe schematic unlock state.
-    for (const RecipeDef& def : m_config.recipes.recipes)
-    {
-        if (def.building == BuildingType::Assembler
-            && def.unlockAtStationLevel.has_value()
-            && def.unlockAtStationLevel.value() == -1)
-        {
-            m_unlockedRecipeSchematicIds.insert(def.id);
-        }
-    }
-
-    recomputeUnlocked();
+    initializeUnlockState();
     placeInitialStructures();
 	registerForEvents();
 }
@@ -174,11 +147,33 @@ void Simulation::reset(unsigned int seed)
     m_waveSystem     = std::make_unique<WaveSystem>(m_config, m_rng);
     m_combatSystem   = std::make_unique<CombatSystem>(m_config);
 
+    initializeUnlockState();
+    placeInitialStructures();
+}
+
+void Simulation::initializeUnlockState()
+{
+    // Cache the ids granted by some unlock group (REQ-LOCK-EXPLICIT); an item
+    // starts locked iff it is granted by a group.
+    m_grantedShipIds.clear();
+    m_grantedModuleIds.clear();
+    m_grantedBuildingIds.clear();
+    m_grantedRecipeIds.clear();
+    for (const UnlockGroupDef& group : m_config.unlocks.groups)
+    {
+        m_grantedShipIds.insert(group.ships.begin(), group.ships.end());
+        m_grantedModuleIds.insert(group.modules.begin(), group.modules.end());
+        m_grantedBuildingIds.insert(group.buildings.begin(), group.buildings.end());
+        m_grantedRecipeIds.insert(group.recipes.begin(), group.recipes.end());
+    }
+
+    m_awardedUnlockGroupIds.clear();
+
     m_schematicLevels.clear();
     for (const ShipDef& def : m_config.ships.ships)
     {
         SchematicState state;
-        state.unlocked = (def.unlockAtStationLevel == -1);
+        state.unlocked = (m_grantedShipIds.count(def.id) == 0);
         m_schematicLevels[def.id] = state;
     }
 
@@ -186,23 +181,23 @@ void Simulation::reset(unsigned int seed)
     for (const ModuleDef& def : m_config.modules.modules)
     {
         SchematicState state;
-        state.unlocked = (def.unlockAtStationLevel == -1);
+        state.unlocked = (m_grantedModuleIds.count(def.id) == 0);
         m_moduleSchematicLevels[def.id] = state;
     }
 
-    m_unlockedRecipeSchematicIds.clear();
-    for (const RecipeDef& def : m_config.recipes.recipes)
+    m_buildingLevels.clear();
+    for (const BuildingDef& def : m_config.buildings.buildings)
     {
-        if (def.building == BuildingType::Assembler
-            && def.unlockAtStationLevel.has_value()
-            && def.unlockAtStationLevel.value() == -1)
-        {
-            m_unlockedRecipeSchematicIds.insert(def.id);
-        }
+        SchematicState state;
+        state.unlocked = (m_grantedBuildingIds.count(def.id) == 0);
+        m_buildingLevels[def.id] = state;
     }
 
+    // Gated assembler recipes start locked; unlocked_at_start recipes are handled
+    // in the REQ-LOCK-IMPLICIT traversal, not tracked here.
+    m_unlockedRecipeSchematicIds.clear();
+
     recomputeUnlocked();
-    placeInitialStructures();
 }
 
 // ---------------------------------------------------------------------------
@@ -236,8 +231,11 @@ void Simulation::apply(const Command& command)
         }
         break;
     }
-    case CommandKind::Demolish:
-        demolish(*static_cast<const DemolishCommand&>(command).id);
+    case CommandKind::Deconstruct:
+        deconstruct(*static_cast<const DeconstructCommand&>(command).id);
+        break;
+    case CommandKind::CancelDeconstruction:
+        cancelDeconstruction(*static_cast<const CancelDeconstructionCommand&>(command).id);
         break;
     case CommandKind::RotateInPlace:
     {
@@ -312,6 +310,7 @@ void Simulation::tick()
 
     // Construction + production pipeline
     m_buildingSystem->tickConstruction(m_currentTick);
+    m_buildingSystem->tickDeconstruction(m_currentTick); // parallel to construction
     m_buildingSystem->tickBeltPull();                    // step 3
     m_buildingSystem->tickProduction(m_currentTick);     // step 4
     m_buildingSystem->tickShipyardProduction(m_currentTick); // step 4b
@@ -628,43 +627,16 @@ void Simulation::tickDeathsAndLoot()
 
 void Simulation::generateSchematicChoices(int destroyedStationLevel)
 {
-    enum class DropType { Ship, Module, Recipe };
-    struct PoolEntry { std::string id; DropType type; };
-    std::vector<PoolEntry> pool;
-
-    // Owned schematics leave the pool (REQ-DEF-SCHEMATIC-DROP): only offer
-    // ship/module schematics that are gated to a station level in range and not
-    // yet unlocked. Schematics with unlock_at_station_level -1 start unlocked, so
-    // they are always owned and never eligible.
-    for (const ShipDef& def : m_config.ships.ships)
+    // Build the eligible pool of unlock groups (REQ-DEF-SCHEMATIC-DROP,
+    // REQ-LOCK-EXPLICIT, REQ-LOCK-PREREQ): not yet awarded, station level in
+    // range, and every prerequisite group already awarded.
+    std::vector<const UnlockGroupDef*> pool;
+    for (const UnlockGroupDef& group : m_config.unlocks.groups)
     {
-        if (def.unlockAtStationLevel < 0 || def.unlockAtStationLevel > destroyedStationLevel) { continue; }
-        if (m_schematicLevels.at(def.id).unlocked) { continue; }
-        if (!prerequisitesSatisfied(def.unlockRequires)) { continue; }
-        pool.push_back({def.id, DropType::Ship});
-    }
-    for (const ModuleDef& def : m_config.modules.modules)
-    {
-        if (def.unlockAtStationLevel < 0 || def.unlockAtStationLevel > destroyedStationLevel) { continue; }
-        if (m_moduleSchematicLevels.at(def.id).unlocked) { continue; }
-        if (!prerequisitesSatisfied(def.unlockRequires)) { continue; }
-        pool.push_back({def.id, DropType::Module});
-    }
-    for (const RecipeDef& def : m_config.recipes.recipes)
-    {
-        if (def.building != BuildingType::Assembler) { continue; }
-        if (!def.unlockAtStationLevel.has_value()) { continue; }
-        const int level = def.unlockAtStationLevel.value();
-        if (level < 0 || level > destroyedStationLevel) { continue; }
-        if (m_unlockedRecipeSchematicIds.count(def.id) > 0) { continue; }
-        bool outputUnlocked = false;
-        for (const RecipeOutput& out : def.outputs)
-        {
-            if (m_unlockedItemIds.count(out.item) > 0) { outputUnlocked = true; break; }
-        }
-        if (!outputUnlocked) { continue; }
-        if (!prerequisitesSatisfied(def.unlockRequires)) { continue; }
-        pool.push_back({def.id, DropType::Recipe});
+        if (m_awardedUnlockGroupIds.count(group.id) > 0) { continue; }
+        if (group.stationLevel < 0 || group.stationLevel > destroyedStationLevel) { continue; }
+        if (!prerequisitesSatisfied(group.requiredGroupIds)) { continue; }
+        pool.push_back(&group);
     }
 
     if (pool.empty()) { return; }
@@ -679,9 +651,6 @@ void Simulation::generateSchematicChoices(int destroyedStationLevel)
     const int numChoices = std::min(static_cast<int>(pool.size()), artifactRolled ? 2 : 3);
     m_pendingSchematicChoices.clear();
 
-    const std::set<std::string> currentShipIds   = getUnlockedShipSchematicIds();
-    const std::set<std::string> currentModuleIds = getUnlockedModuleSchematicIds();
-
     for (int i = 0; i < numChoices; ++i)
     {
         std::uniform_int_distribution<int> dist(0, static_cast<int>(pool.size()) - 1 - i);
@@ -689,68 +658,67 @@ void Simulation::generateSchematicChoices(int destroyedStationLevel)
         const std::size_t rollIdx = static_cast<std::size_t>(roll);
         const std::size_t endIdx  = pool.size() - 1 - static_cast<std::size_t>(i);
         std::swap(pool[rollIdx], pool[endIdx]);
-        const PoolEntry& entry = pool[endIdx];
 
-        SchematicChoiceOption option;
-        option.schematicId = entry.id;
-
-        if (entry.type == DropType::Ship)
-        {
-            option.type = SchematicType::Ship;
-            option.displayName = toDisplayName(entry.id);
-        }
-        else if (entry.type == DropType::Module)
-        {
-            option.type = SchematicType::Module;
-            option.displayName = toDisplayName(entry.id);
-        }
-        else
-        {
-            option.type = SchematicType::Recipe;
-            option.displayName = toDisplayName(entry.id);
-        }
-
-        // REQ-DEF-SCHEMATIC-DROP: preview recipes newly implicitly unlocked by this option.
-        std::set<std::string> hypotheticalShipIds              = currentShipIds;
-        std::set<std::string> hypotheticalModuleIds            = currentModuleIds;
-        std::set<std::string> hypotheticalRecipeSchematicIds   = m_unlockedRecipeSchematicIds;
-
-        if (entry.type == DropType::Ship)
-        {
-            hypotheticalShipIds.insert(entry.id);
-        }
-        else if (entry.type == DropType::Module)
-        {
-            hypotheticalModuleIds.insert(entry.id);
-        }
-        else if (entry.type == DropType::Recipe)
-        {
-            hypotheticalRecipeSchematicIds.insert(entry.id);
-        }
-
-        const UnlockedSets hypothetical = computeUnlockedSets(
-            hypotheticalShipIds, hypotheticalModuleIds, hypotheticalRecipeSchematicIds);
-        option.newlyUnlockedRecipeIds = computeNewlyUnlockedRecipeIds(hypothetical);
-
-        m_pendingSchematicChoices.push_back(option);
+        m_pendingSchematicChoices.push_back(makeUnlockOption(*pool[endIdx]));
     }
 
     if (artifactRolled)
     {
         SchematicChoiceOption artifactOption;
-        artifactOption.schematicId  = "";
-        artifactOption.type         = SchematicType::Artifact;
-        artifactOption.displayName  = "Artifact";
+        artifactOption.isArtifact  = true;
+        artifactOption.displayName = "Artifact";
         m_pendingSchematicChoices.push_back(std::move(artifactOption));
     }
 }
 
+SchematicChoiceOption Simulation::makeUnlockOption(const UnlockGroupDef& group) const
+{
+    SchematicChoiceOption option;
+    option.isArtifact    = false;
+    option.unlockGroupId = group.id;
+    option.displayName   = toDisplayName(group.id);
+
+    for (const std::string& id : group.ships)
+    {
+        option.grantedItems.push_back({SchematicType::Ship, id, toDisplayName(id)});
+    }
+    for (const std::string& id : group.modules)
+    {
+        option.grantedItems.push_back({SchematicType::Module, id, toDisplayName(id)});
+    }
+    for (const std::string& id : group.buildings)
+    {
+        option.grantedItems.push_back({SchematicType::Building, id, toDisplayName(id)});
+    }
+    for (const std::string& id : group.recipes)
+    {
+        option.grantedItems.push_back({SchematicType::Recipe, id, toDisplayName(id)});
+    }
+
+    // REQ-DEF-SCHEMATIC-DROP: preview recipes newly implicitly unlocked by
+    // awarding this whole group. Seed the hypothetical explicit-unlock sets with
+    // every grant (ship + module materials via step 1a, recipe outputs via step
+    // 1b), then diff against the current implicit set.
+    std::set<std::string> hypotheticalShipIds            = getUnlockedShipSchematicIds();
+    std::set<std::string> hypotheticalModuleIds          = getUnlockedModuleSchematicIds();
+    std::set<std::string> hypotheticalRecipeSchematicIds = m_unlockedRecipeSchematicIds;
+    for (const std::string& id : group.ships)   { hypotheticalShipIds.insert(id); }
+    for (const std::string& id : group.modules) { hypotheticalModuleIds.insert(id); }
+    for (const std::string& id : group.recipes) { hypotheticalRecipeSchematicIds.insert(id); }
+
+    const UnlockedSets hypothetical = computeUnlockedSets(
+        hypotheticalShipIds, hypotheticalModuleIds, hypotheticalRecipeSchematicIds);
+    option.newlyUnlockedRecipeIds = computeNewlyUnlockedRecipeIds(hypothetical);
+
+    return option;
+}
+
 void Simulation::applySchematicChoice(int choiceIndex)
 {
     assert(choiceIndex >= 0 && choiceIndex < static_cast<int>(m_pendingSchematicChoices.size()));
     const SchematicChoiceOption& chosen = m_pendingSchematicChoices[static_cast<std::size_t>(choiceIndex)];
 
-    if (chosen.type == SchematicType::Artifact)
+    if (chosen.isArtifact)
     {
         m_artifactCount += 1;
         if (m_artifactCount >= m_config.world.artifacts.artifactWinCount)
@@ -761,16 +729,18 @@ void Simulation::applySchematicChoice(int choiceIndex)
         return;
     }
 
-    if (chosen.type == SchematicType::Recipe)
+    // Award the whole unlock group (REQ-DEF-SCHEMATIC-DROP): unlock every granted
+    // ship, module, building, and assembler recipe at once.
+    m_awardedUnlockGroupIds.insert(chosen.unlockGroupId);
+    for (const GrantedSchematic& grant : chosen.grantedItems)
     {
-        m_unlockedRecipeSchematicIds.insert(chosen.schematicId);
-    }
-    else
-    {
-        SchematicState& state = (chosen.type == SchematicType::Module)
-            ? m_moduleSchematicLevels.at(chosen.schematicId)
-            : m_schematicLevels.at(chosen.schematicId);
-        state.unlocked = true;
+        switch (grant.type)
+        {
+        case SchematicType::Ship:     m_schematicLevels.at(grant.id).unlocked = true;       break;
+        case SchematicType::Module:   m_moduleSchematicLevels.at(grant.id).unlocked = true; break;
+        case SchematicType::Building: m_buildingLevels.at(grant.id).unlocked = true;        break;
+        case SchematicType::Recipe:   m_unlockedRecipeSchematicIds.insert(grant.id);        break;
+        }
     }
 
     recomputeUnlocked();
@@ -809,28 +779,13 @@ std::set<std::string> Simulation::getUnlockedModuleSchematicIds() const
     return ids;
 }
 
-bool Simulation::isSchematicIdExplicitlyUnlocked(const std::string& schematicId) const
+bool Simulation::prerequisitesSatisfied(const std::vector<std::string>& requiredGroupIds) const
 {
-    // A prerequisite is satisfied only by an explicitly-unlocked schematic
-    // (REQ-LOCK-PREREQ): a ship or module schematic marked unlocked, or a recipe
-    // schematic in the explicit-unlock set. Cross-type ids are looked up with
-    // find/count so an id from one namespace never throws against another.
-    const std::map<std::string, SchematicState>::const_iterator shipIt =
-        m_schematicLevels.find(schematicId);
-    if (shipIt != m_schematicLevels.end() && shipIt->second.unlocked) { return true; }
-
-    const std::map<std::string, SchematicState>::const_iterator moduleIt =
-        m_moduleSchematicLevels.find(schematicId);
-    if (moduleIt != m_moduleSchematicLevels.end() && moduleIt->second.unlocked) { return true; }
-
-    return m_unlockedRecipeSchematicIds.count(schematicId) > 0;
-}
-
-bool Simulation::prerequisitesSatisfied(const std::vector<std::string>& unlockRequires) const
-{
-    for (const std::string& requiredId : unlockRequires)
+    // A prerequisite is satisfied only once the named unlock group has been
+    // awarded (REQ-LOCK-PREREQ).
+    for (const std::string& groupId : requiredGroupIds)
     {
-        if (!isSchematicIdExplicitlyUnlocked(requiredId)) { return false; }
+        if (m_awardedUnlockGroupIds.count(groupId) == 0) { return false; }
     }
     return true;
 }
@@ -860,9 +815,11 @@ Simulation::UnlockedSets Simulation::computeUnlockedSets(
     }
     for (const RecipeDef& def : m_config.recipes.recipes)
     {
+        // An assembler recipe seeds the base set when it is explicitly available:
+        // flagged unlocked_at_start (base recipes the graph can't reach), or a
+        // gated recipe whose unlock group has been awarded (REQ-LOCK-EXPLICIT).
         if (def.building == BuildingType::Assembler
-            && def.unlockAtStationLevel.has_value()
-            && unlockedRecipeSchematicIds.count(def.id) > 0)
+            && (def.unlockedAtStart || unlockedRecipeSchematicIds.count(def.id) > 0))
         {
             for (const RecipeOutput& out : def.outputs)
             {
@@ -883,8 +840,10 @@ Simulation::UnlockedSets Simulation::computeUnlockedSets(
             {
                 continue;
             }
+            // Skip a gated assembler recipe (granted by an unlock group) whose
+            // group has not yet been awarded (REQ-LOCK-IMPLICIT step 2).
             if (recipe.building == BuildingType::Assembler
-                && recipe.unlockAtStationLevel.has_value()
+                && m_grantedRecipeIds.count(recipe.id) > 0
                 && unlockedRecipeSchematicIds.count(recipe.id) == 0)
             {
                 continue;
@@ -1000,6 +959,8 @@ unsigned long long Simulation::computeStateChecksum() const
     // Schematic / unlock state (std::map and std::set iterate in sorted order).
     appendSchematicMap(hasher, m_schematicLevels);
     appendSchematicMap(hasher, m_moduleSchematicLevels);
+    appendSchematicMap(hasher, m_buildingLevels);
+    appendStringSet(hasher, m_awardedUnlockGroupIds);
     appendStringSet(hasher, m_unlockedRecipeSchematicIds);
     appendStringSet(hasher, m_unlockedRecipeIds);
     appendStringSet(hasher, m_unlockedItemIds);
@@ -1193,8 +1154,28 @@ bool Simulation::isModuleSchematicUnlocked(const std::string& moduleId) const
     return it->second.unlocked;
 }
 
+bool Simulation::isBuildingUnlocked(BuildingType type) const
+{
+    const BuildingDef* def = m_config.buildings.findBuildingDef(type);
+    if (def == nullptr)
+    {
+        // Types without a config entry (e.g. HQ, defence stations) are unrestricted.
+        return true;
+    }
+    const std::map<std::string, SchematicState>::const_iterator it =
+        m_buildingLevels.find(def->id);
+    return it == m_buildingLevels.end() ? true : it->second.unlocked;
+}
+
 std::optional<BuildingId> Simulation::tryPlaceBuilding(BuildingType type, QPoint anchor, Rotation rotation)
 {
+    // Locked building types cannot be placed (REQ-LOCK-BUILDING); the build menu
+    // hides them, this is the simulation-side backstop (e.g. blueprint placement).
+    if (!isBuildingUnlocked(type))
+    {
+        return std::nullopt;
+    }
+
     if (!m_buildingSystem->isPlacementValid(type, anchor, rotation))
     {
         return std::nullopt;
@@ -1217,9 +1198,14 @@ std::optional<BuildingId> Simulation::tryPlaceBuilding(BuildingType type, QPoint
     return m_buildingSystem->place(type, anchor, rotation, m_currentTick);
 }
 
-void Simulation::demolish(BuildingId id)
+void Simulation::deconstruct(BuildingId id)
 {
-    m_buildingBlocksStock += m_buildingSystem->demolish(id);
+    m_buildingBlocksStock += m_buildingSystem->deconstruct(id, m_currentTick);
+}
+
+void Simulation::cancelDeconstruction(BuildingId id)
+{
+    m_buildingSystem->cancelDeconstruction(id);
 }
 
 BuildingSystem& Simulation::getBuildingsMutable()

src/lib/sim/Simulation.h

@@ -100,6 +100,10 @@ public:
     bool isRecipeUnlocked(const std::string& recipeId) const;
     bool isItemUnlocked(const std::string& itemId) const;
 
+    // Building unlock query (REQ-LOCK-BUILDING). True if the building type is not
+    // gated by any unlock group, or its granting group has been awarded.
+    bool isBuildingUnlocked(BuildingType type) const;
+
     // -- Determinism (see docs/replay_design.md) -----------------------------
     // 64-bit fingerprint of the RNG stream state. Cheap; written to the replay
     // file periodically + after each command for desync detection.
@@ -135,8 +139,13 @@ private:
     // Returns the new entity id, or nullopt if blocks are insufficient.
     std::optional<BuildingId> tryPlaceBuilding(BuildingType type, QPoint anchor, Rotation rotation);
 
-    // Demolishes the building with the given id and refunds building blocks.
-    void demolish(BuildingId id);
+    // Marks the building with the given id for demolition: a construction site is
+    // removed instantly (full refund), a built building is queued for timed
+    // deconstruction (REQ-BLD-DECON-QUEUE), refunded on completion.
+    void deconstruct(BuildingId id);
+
+    // Takes a queued building back out of the deconstruction queue (REQ-BLD-DECON-QUEUE).
+    void cancelDeconstruction(BuildingId id);
 
     // Applies the player's chosen schematic from the pending choices.
     // choiceIndex must be in [0, pendingChoices.size()).
@@ -196,6 +205,24 @@ private:
     };
     std::map<std::string, SchematicState> m_schematicLevels;
     std::map<std::string, SchematicState> m_moduleSchematicLevels;
+    std::map<std::string, SchematicState> m_buildingLevels;
+
+    // Unlock groups awarded so far (REQ-LOCK-EXPLICIT). Group ids.
+    std::set<std::string> m_awardedUnlockGroupIds;
+
+    // Ids granted by some unlock group, per kind — cached from config at init.
+    // An item starts locked iff it appears in the corresponding set.
+    std::set<std::string> m_grantedShipIds;
+    std::set<std::string> m_grantedModuleIds;
+    std::set<std::string> m_grantedBuildingIds;
+    std::set<std::string> m_grantedRecipeIds;
+
+    // Builds the granted-id sets and initializes all per-item unlock maps from
+    // them (shared by the constructor and reset). Ends with recomputeUnlocked().
+    void initializeUnlockState();
+
+    // Builds a schematic choice option for one unlock group (REQ-DEF-SCHEMATIC-DROP).
+    SchematicChoiceOption makeUnlockOption(const UnlockGroupDef& group) const;
 
     // Determinism helpers — fold sub-state into the hasher in deterministic order.
     static void appendSchematicMap(Hasher& hasher,
@@ -228,11 +255,8 @@ private:
     std::set<std::string> getUnlockedShipSchematicIds() const;
     std::set<std::string> getUnlockedModuleSchematicIds() const;
 
-    // True if schematicId names a currently explicitly-unlocked ship, module, or
-    // assembler recipe schematic (REQ-LOCK-PREREQ satisfaction basis).
-    bool isSchematicIdExplicitlyUnlocked(const std::string& schematicId) const;
-    // True if every prerequisite in unlockRequires is explicitly unlocked (REQ-LOCK-PREREQ).
-    bool prerequisitesSatisfied(const std::vector<std::string>& unlockRequires) const;
+    // True if every prerequisite unlock group has been awarded (REQ-LOCK-PREREQ).
+    bool prerequisitesSatisfied(const std::vector<std::string>& requiredGroupIds) const;
 
     // Ids (sorted alphabetically by display name) of the recipes in
     // hypothetical.recipeIds that are not yet in m_unlockedRecipeIds.

src/test/ArtifactWinConditionTest.cpp

@@ -36,7 +36,7 @@ static int findArtifactChoiceIndex(const Simulation& sim)
     const auto& choices = sim.getPendingSchematicChoices();
     for (int i = 0; i < static_cast<int>(choices.size()); ++i)
     {
-        if (choices[static_cast<std::size_t>(i)].type == SchematicType::Artifact)
+        if (choices[static_cast<std::size_t>(i)].isArtifact)
         {
             return i;
         }
@@ -86,7 +86,7 @@ TEST_CASE("ArtifactWinCondition: artifact option appears when chance formula ret
     const auto& choices = sim.getPendingSchematicChoices();
 
     const long artifactCount = std::count_if(choices.begin(), choices.end(),
-        [](const SchematicChoiceOption& opt) { return opt.type == SchematicType::Artifact; });
+        [](const SchematicChoiceOption& opt) { return opt.isArtifact; });
     CHECK(artifactCount == 1);
     // Exactly 2 schematic picks + 1 artifact (or fewer if pool was small)
     CHECK(choices.size() <= 3);
@@ -105,7 +105,7 @@ TEST_CASE("ArtifactWinCondition: at most 2 schematic options accompany the artif
     const auto& choices = sim.getPendingSchematicChoices();
 
     const long schematicCount = std::count_if(choices.begin(), choices.end(),
-        [](const SchematicChoiceOption& opt) { return opt.type != SchematicType::Artifact; });
+        [](const SchematicChoiceOption& opt) { return !opt.isArtifact; });
     CHECK(schematicCount <= 2);
 }
 
@@ -161,7 +161,7 @@ TEST_CASE("ArtifactWinCondition: selecting a non-artifact option does not increm
     // Pick the first non-artifact choice.
     const auto& choices = sim.getPendingSchematicChoices();
     const auto it = std::find_if(choices.begin(), choices.end(),
-        [](const SchematicChoiceOption& opt) { return opt.type != SchematicType::Artifact; });
+        [](const SchematicChoiceOption& opt) { return !opt.isArtifact; });
     REQUIRE(it != choices.end());
 
     SimulationTestAccess::applySchematicChoice(sim,static_cast<int>(it - choices.begin()));

src/test/BeltSystemTest.cpp

@@ -974,7 +974,7 @@ TEST_CASE("BeltSystem: unpaired entry blocks items at front", "[belt]")
     REQUIRE(bs.peekItem(Port{QPoint(3, 0), Rotation::East}).has_value());
 }
 
-TEST_CASE("BeltSystem: demolish entry discards transit items", "[belt]")
+TEST_CASE("BeltSystem: deconstruct entry discards transit items", "[belt]")
 {
     BeltSystem bs(kFastBeltSpeed);
 

src/test/BuildingConfigTest.cpp

@@ -1,5 +1,7 @@
 #include "catch.hpp"
 
+#include <algorithm>
+
 #include "Building.h"
 #include "BuildingConfig.h"
 #include "BuildingSystem.h"
@@ -46,7 +48,17 @@ const ShipDef* findAvailableSchematic(const GameConfig& cfg)
 {
     for (const ShipDef& def : cfg.ships.ships)
     {
-        if (def.unlockAtStationLevel == -1) { return &def; }
+        // A ship starts unlocked iff no unlock group grants it (REQ-LOCK-EXPLICIT).
+        bool granted = false;
+        for (const UnlockGroupDef& group : cfg.unlocks.groups)
+        {
+            if (std::find(group.ships.begin(), group.ships.end(), def.id) != group.ships.end())
+            {
+                granted = true;
+                break;
+            }
+        }
+        if (!granted) { return &def; }
     }
     return nullptr;
 }

src/test/BuildingTest.cpp

@@ -58,6 +58,7 @@ static void runTicks(BuildingSystem& bs, BeltSystem& belts, int n, Tick& tick)
     for (int i = 0; i < n; ++i)
     {
         bs.tickConstruction(tick);
+        bs.tickDeconstruction(tick);
         bs.tickBeltPull();
         bs.tickProduction(tick);
         bs.tickOutputBelts();
@@ -265,33 +266,20 @@ TEST_CASE("BuildingSystem: placed building enters construction queue", "[buildin
     REQUIRE(bs.findSite(id) != nullptr);
 }
 
-TEST_CASE("BuildingSystem: demolish frees tiles and returns refund", "[building]")
+TEST_CASE("BuildingSystem: deconstructing a construction site removes it instantly with full refund",
+          "[building]")
 {
-    const GameConfig cfg = loadConfig();
-    BeltSystem belts(cfg.world.beltSpeed_tps);
-    int stock = 0;
-    std::mt19937 rng(0);
-    BuildingId nextBuildingId = 1;
-    BuildingSystem bs(cfg, belts,
-                      [&nextBuildingId]() { return nextBuildingId++; },
-                      [&stock](int n) { stock += n; },
-                      [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
-                      [](const std::string&) -> bool { return true; },
-                      rng);
+    PlacementFixture f;
+    const BuildingId id =
+        f.bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0).value();
 
-    const BuildingId id = bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0).value();
+    // Still queued for construction (not yet built): instant removal, full cost
+    // refunded immediately, never entering the deconstruction queue (REQ-BLD-DECONSTRUCT).
+    const int refund = f.bs.deconstruct(id, 0);
 
-	// Miner construction_time_seconds = 10.  completesAt = secondsToTicks(10) = 300.
-	// We need to process tick 300 itself, so run 301 ticks (ticks 0..300).
-	Tick tick = 0;
-	runTicks(bs, belts, static_cast<int>(secondsToTicks(10.0)) + 1, tick);
-
-    const int refund = bs.demolish(id);
-
-    // Miner cost = 15, refund = floor(15 * 75 / 100) = 11.
-    REQUIRE(refund == 15 * cfg.world.refundPercentage / 100);
-    REQUIRE_FALSE(bs.isTileOccupied(QPoint(0, 0)));
-    REQUIRE(bs.getAllSites().empty());
+    REQUIRE(refund == 15);  // Miner cost = 15
+    REQUIRE_FALSE(f.bs.isTileOccupied(QPoint(0, 0)));
+    REQUIRE(f.bs.getAllSites().empty());
 }
 
 // ---------------------------------------------------------------------------
@@ -364,6 +352,147 @@ TEST_CASE("BuildingSystem: construction completes after configured duration", "[
     REQUIRE(bs.findBuilding(id) != nullptr);
 }
 
+// ---------------------------------------------------------------------------
+// Deconstruction queue (REQ-BLD-DECON-QUEUE)
+// ---------------------------------------------------------------------------
+
+// Runs ticks until the building with the given id is operational, or fails.
+static void runUntilBuilt(PlacementFixture& f, BuildingId id, Tick& tick)
+{
+    for (int i = 0; i < 100000 && f.bs.findBuilding(id) == nullptr; ++i)
+    {
+        runTicks(f.bs, f.belts, 1, tick);
+    }
+    REQUIRE(f.bs.findBuilding(id) != nullptr);
+}
+
+TEST_CASE("BuildingSystem: deconstructing a built building queues it; refund credited on completion",
+          "[building][decon]")
+{
+    PlacementFixture f;
+    const BuildingId id =
+        f.bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0).value();
+
+    Tick tick = 0;
+    runUntilBuilt(f, id, tick);
+
+    // Deconstructing a built building returns nothing immediately and queues it,
+    // stopping it operating while its tiles stay occupied (REQ-BLD-DECON-QUEUE).
+    const int refund = f.bs.deconstruct(id, tick);
+    REQUIRE(refund == 0);
+    REQUIRE(f.bs.isQueuedForDeconstruction(id));
+    REQUIRE(f.bs.isTileOccupied(QPoint(0, 0)));
+    REQUIRE(f.stock == 0);
+
+    // After the deconstruction time (0.1s = 3 ticks) it is removed and the partial
+    // refund (15 * 75 / 100 = 11) is credited exactly once.
+    runTicks(f.bs, f.belts, static_cast<int>(secondsToTicks(0.1)) + 1, tick);
+    REQUIRE(f.bs.findBuilding(id) == nullptr);
+    REQUIRE_FALSE(f.bs.isTileOccupied(QPoint(0, 0)));
+    REQUIRE(f.stock == 15 * f.cfg.world.refundPercentage / 100);
+}
+
+TEST_CASE("BuildingSystem: deconstruction queue removes one building at a time", "[building][decon]")
+{
+    PlacementFixture f;
+    const BuildingId a = f.bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0).value();
+    const BuildingId b = f.bs.place(BuildingType::Miner, QPoint(5, 5), Rotation::East, 0).value();
+
+    Tick tick = 0;
+    runUntilBuilt(f, a, tick);
+    runUntilBuilt(f, b, tick);
+
+    // Queue both in one tick; 'a' is at the front of the deconstruction queue.
+    f.bs.deconstruct(a, tick);
+    f.bs.deconstruct(b, tick);
+    REQUIRE(f.bs.isQueuedForDeconstruction(a));
+    REQUIRE(f.bs.isQueuedForDeconstruction(b));
+
+    // After one deconstruction interval only the front building is gone; the
+    // second is still queued and its refund not yet credited.
+    runTicks(f.bs, f.belts, static_cast<int>(secondsToTicks(0.1)) + 1, tick);
+    REQUIRE(f.bs.findBuilding(a) == nullptr);
+    REQUIRE(f.bs.findBuilding(b) != nullptr);
+    REQUIRE(f.bs.isQueuedForDeconstruction(b));
+    REQUIRE(f.stock == 15 * f.cfg.world.refundPercentage / 100);
+
+    // The second drains next.
+    runTicks(f.bs, f.belts, static_cast<int>(secondsToTicks(0.1)) + 2, tick);
+    REQUIRE(f.bs.findBuilding(b) == nullptr);
+    REQUIRE(f.stock == 2 * (15 * f.cfg.world.refundPercentage / 100));
+}
+
+TEST_CASE("BuildingSystem: cancelling deconstruction resumes the building with no refund",
+          "[building][decon]")
+{
+    PlacementFixture f;
+    const BuildingId id =
+        f.bs.place(BuildingType::Miner, QPoint(0, 0), Rotation::East, 0).value();
+
+    Tick tick = 0;
+    runUntilBuilt(f, id, tick);
+
+    f.bs.deconstruct(id, tick);
+    REQUIRE(f.bs.isQueuedForDeconstruction(id));
+
+    // Un-queue before it drains: it operates again, no refund, tiles still occupied.
+    f.bs.cancelDeconstruction(id);
+    REQUIRE_FALSE(f.bs.isQueuedForDeconstruction(id));
+    REQUIRE(f.bs.findBuilding(id) != nullptr);
+    REQUIRE(f.bs.isTileOccupied(QPoint(0, 0)));
+    REQUIRE(f.stock == 0);
+
+    // It is never removed even after more than a deconstruction interval passes.
+    runTicks(f.bs, f.belts, static_cast<int>(secondsToTicks(0.1)) + 5, tick);
+    REQUIRE(f.bs.findBuilding(id) != nullptr);
+    REQUIRE(f.stock == 0);
+}
+
+TEST_CASE("BuildingSystem: queued belt stops transporting; cancel restores it", "[building][decon]")
+{
+    PlacementFixture f;
+    const BuildingId id =
+        f.bs.place(BuildingType::Belt, QPoint(0, 0), Rotation::East, 0).value();
+
+    Tick tick = 0;
+    runUntilBuilt(f, id, tick);
+    REQUIRE(f.belts.tryPutItem(QPoint(0, 0), makeItem("iron_ore"), Rotation::East));
+
+    // Queuing a belt unregisters its tile from the belt subsystem, so it no longer
+    // accepts or transports items, though the tile stays occupied (REQ-BLD-DECON-QUEUE).
+    f.bs.deconstruct(id, tick);
+    REQUIRE_FALSE(f.belts.tryPutItem(QPoint(0, 0), makeItem("iron_ore"), Rotation::East));
+    REQUIRE(f.bs.isTileOccupied(QPoint(0, 0)));
+
+    // Un-queuing re-registers the belt tile so it transports again.
+    f.bs.cancelDeconstruction(id);
+    REQUIRE(f.belts.tryPutItem(QPoint(0, 0), makeItem("iron_ore"), Rotation::East));
+}
+
+TEST_CASE("BuildingSystem: splitter filters survive a queue/un-queue round-trip", "[building][decon]")
+{
+    PlacementFixture f;
+    const BuildingId id =
+        f.bs.place(BuildingType::Splitter, QPoint(0, 0), Rotation::East, 0).value();
+
+    Tick tick = 0;
+    runUntilBuilt(f, id, tick);
+
+    f.belts.setSplitterFilters(QPoint(0, 0), {ItemType{"iron_ore"}}, {});
+
+    // Queue: the belt subsystem tile (and its filters) are unregistered, but the
+    // filters are captured so an un-queue can restore them.
+    f.bs.deconstruct(id, tick);
+    REQUIRE_FALSE(f.belts.getSplitterInfo(QPoint(0, 0)).has_value());
+
+    f.bs.cancelDeconstruction(id);
+    const std::optional<BeltSystem::SplitterInfo> info = f.belts.getSplitterInfo(QPoint(0, 0));
+    REQUIRE(info.has_value());
+    REQUIRE(info->filterA.size() == 1);
+    REQUIRE(info->filterA[0].id == "iron_ore");
+    REQUIRE(info->filterB.empty());
+}
+
 TEST_CASE("BuildingSystem: second building starts after first completes", "[building]")
 {
     const GameConfig cfg = loadConfig();

src/test/CMakeLists.txt

@@ -25,6 +25,7 @@ add_files(
     ThreatCostCalculatorTest.cpp
     RecipeSchematicTest.cpp
     UnlockPrereqTest.cpp
+    UnlockGroupTest.cpp
     ArtifactWinConditionTest.cpp
     DeterminismTest.cpp
     CommandTest.cpp

src/test/CommandTest.cpp

@@ -10,6 +10,7 @@
 #include "Rotation.h"
 #include "Simulation.h"
 #include "SimulationTestAccess.h"
+#include "Tick.h"
 
 namespace
 {
@@ -58,7 +59,7 @@ TEST_CASE("apply(PlaceBuildingCommand) with recipe matches place-then-setRecipe"
     REQUIRE(viaCommand.computeStateChecksum() == viaDirect.computeStateChecksum());
 }
 
-TEST_CASE("apply(DemolishCommand) matches direct demolish", "[command]")
+TEST_CASE("apply(DeconstructCommand) matches direct deconstruct", "[command]")
 {
     Simulation viaCommand(loadConfig(), 99);
     Simulation viaDirect(loadConfig(), 99);
@@ -69,11 +70,40 @@ TEST_CASE("apply(DemolishCommand) matches direct demolish", "[command]")
         SimulationTestAccess::place(viaDirect, BuildingType::Miner, QPoint(-3, 0), Rotation::East).value();
     REQUIRE(idA == idB);
 
-    DemolishCommand command;
+    DeconstructCommand command;
     command.id = idA;
     viaCommand.apply(command);
 
-    SimulationTestAccess::demolish(viaDirect, idB);
+    SimulationTestAccess::deconstruct(viaDirect, idB);
+
+    REQUIRE(viaCommand.computeStateChecksum() == viaDirect.computeStateChecksum());
+}
+
+TEST_CASE("apply(CancelDeconstructionCommand) matches direct cancelDeconstruction", "[command]")
+{
+    Simulation viaCommand(loadConfig(), 99);
+    Simulation viaDirect(loadConfig(), 99);
+
+    const BuildingId idA =
+        SimulationTestAccess::place(viaCommand, BuildingType::Miner, QPoint(-3, 0), Rotation::East).value();
+    const BuildingId idB =
+        SimulationTestAccess::place(viaDirect, BuildingType::Miner, QPoint(-3, 0), Rotation::East).value();
+    REQUIRE(idA == idB);
+
+    // Build the miners, then queue both for deconstruction identically.
+    for (int i = 0; i < static_cast<int>(secondsToTicks(10.0)) + 1; ++i)
+    {
+        viaCommand.tick();
+        viaDirect.tick();
+    }
+    SimulationTestAccess::deconstruct(viaCommand, idA);
+    SimulationTestAccess::deconstruct(viaDirect, idB);
+
+    CancelDeconstructionCommand command;
+    command.id = idA;
+    viaCommand.apply(command);
+
+    SimulationTestAccess::cancelDeconstruction(viaDirect, idB);
 
     REQUIRE(viaCommand.computeStateChecksum() == viaDirect.computeStateChecksum());
 }

src/test/ConfigLoaderTest.cpp

@@ -10,6 +10,7 @@
 
 #include "BuildingType.h"
 #include "ConfigLoader.h"
+#include "UnlocksConfig.h"
 
 namespace
 {
@@ -210,6 +211,7 @@ TEST_CASE("Missing field in world.toml is rejected with the field path", "[confi
 [world]
 height_tiles = 60
 refund_percentage = 75
+deconstruction_time_seconds = 0.1
 scrap_despawn_seconds = 30
 scrap_per_threat = 0.01
 tile_size_m = 10
@@ -261,6 +263,7 @@ TEST_CASE("Malformed formula in world.toml is rejected with field identification
 [world]
 height_tiles = 60
 refund_percentage = 75
+deconstruction_time_seconds = 0.1
 scrap_despawn_seconds = 30
 scrap_per_threat = 0.01
 tile_size_m = 10
@@ -313,6 +316,7 @@ TEST_CASE("Inverted wave gap range is rejected", "[config]")
 [world]
 height_tiles = 60
 refund_percentage = 75
+deconstruction_time_seconds = 0.1
 scrap_despawn_seconds = 30
 scrap_per_threat = 0.01
 tile_size_m = 10
@@ -407,99 +411,42 @@ void copyConfigInto(const std::filesystem::path& dir)
 
 } // namespace
 
-TEST_CASE("unlock_requires parses into a ship def", "[config]")
+TEST_CASE("loadUnlocks parses id, station_level, requires, and grants", "[config]")
 {
     TempConfigDir dir;
-    writeFile(dir.path() / "ships.toml", R"(
-[[ship]]
-id = "alpha"
-unlock_at_station_level = 1
-unlock_requires = ["beta", "gamma"]
-layout = ["O"]
-[ship.schematic]
-materials = []
-production_time_seconds = 5
-[ship.health]
-hp = 10
-[ship.movement]
-speed_mps = 1
-main_acceleration_mpss = 1
-maneuvering_acceleration_mpss = 1
-angular_acceleration_radpss = 1
-max_rotation_speed_radps = 1
-[ship.sensor]
-sensor_range_m = 10
+    writeFile(dir.path() / "unlocks.toml", R"(
+[[unlock]]
+id = "base"
+station_level = 0
+buildings = ["salvage_bay"]
+
+[[unlock]]
+id = "gated"
+station_level = 3
+requires = ["base"]
+ships = ["cruiser"]
+modules = ["railgun_m"]
+recipes = ["shortcut_steel_plate"]
 )");
 
-    const ShipsConfig cfg = ConfigLoader::loadShips((dir.path() / "ships.toml").string());
-    REQUIRE(cfg.ships.size() == 1);
-    CHECK(cfg.ships[0].unlockRequires == std::vector<std::string>{"beta", "gamma"});
+    const UnlocksConfig cfg = ConfigLoader::loadUnlocks((dir.path() / "unlocks.toml").string());
+    REQUIRE(cfg.groups.size() == 2);
+    CHECK(cfg.groups[0].id == "base");
+    CHECK(cfg.groups[0].stationLevel == 0);
+    CHECK(cfg.groups[0].buildings == std::vector<std::string>{"salvage_bay"});
+    CHECK(cfg.groups[1].requiredGroupIds == std::vector<std::string>{"base"});
+    CHECK(cfg.groups[1].ships == std::vector<std::string>{"cruiser"});
+    CHECK(cfg.groups[1].modules == std::vector<std::string>{"railgun_m"});
+    CHECK(cfg.groups[1].recipes == std::vector<std::string>{"shortcut_steel_plate"});
 }
 
-TEST_CASE("unlock_requires parses into a module def", "[config]")
-{
-    TempConfigDir dir;
-    writeFile(dir.path() / "modules.toml", R"(
-[[module]]
-id = "m1"
-unlock_at_station_level = 0
-unlock_requires = ["dep"]
-surface_mask = ["O"]
-materials = [{item = "iron_ingot", amount = 1}]
-production_time_seconds = 1
-fill_color = "#ffffff"
-glyph = "M"
-)");
-
-    const ModulesConfig cfg = ConfigLoader::loadModules((dir.path() / "modules.toml").string());
-    REQUIRE(cfg.modules.size() == 1);
-    CHECK(cfg.modules[0].unlockRequires == std::vector<std::string>{"dep"});
-}
-
-TEST_CASE("unlock_requires parses only for assembler recipes", "[config]")
-{
-    TempConfigDir dir;
-    writeFile(dir.path() / "recipes.toml", R"(
-[[recipe]]
-id = "gated_asm"
-building = "assembler"
-unlock_at_station_level = 1
-unlock_requires = ["prereq_recipe"]
-inputs = []
-outputs = [{item = "foo", amount = 1}]
-duration_seconds = 1.0
-
-[[recipe]]
-id = "a_miner"
-building = "miner"
-unlock_requires = ["ignored"]
-inputs = []
-outputs = [{item = "ore", amount = 1}]
-duration_seconds = 1.0
-)");
-
-    const RecipesConfig cfg = ConfigLoader::loadRecipes((dir.path() / "recipes.toml").string());
-    REQUIRE(cfg.recipes.size() == 2);
-    CHECK(cfg.recipes[0].unlockRequires == std::vector<std::string>{"prereq_recipe"});
-    // The field is only consumed for assembler recipe schematics; a miner recipe
-    // leaves it unparsed (empty).
-    CHECK(cfg.recipes[1].unlockRequires.empty());
-}
-
-TEST_CASE("unlock_requires referencing an unknown schematic is rejected at load", "[config]")
+TEST_CASE("validateUnlocks rejects a grant that names no definition", "[config]")
 {
     TempConfigDir dir;
     copyConfigInto(dir.path());
 
-    std::ofstream out((dir.path() / "recipes.toml").string(), std::ios::app);
-    out << "\n[[recipe]]\n"
-           "id = \"gated_bogus\"\n"
-           "building = \"assembler\"\n"
-           "unlock_at_station_level = 1\n"
-           "unlock_requires = [\"___does_not_exist___\"]\n"
-           "inputs = []\n"
-           "outputs = [{item = \"circuit_board\", amount = 1}]\n"
-           "duration_seconds = 1.0\n";
+    std::ofstream out((dir.path() / "unlocks.toml").string(), std::ios::app);
+    out << "\n[[unlock]]\nid = \"bogus\"\nstation_level = 0\nships = [\"___nope___\"]\n";
     out.close();
 
     try
@@ -509,26 +456,103 @@ TEST_CASE("unlock_requires referencing an unknown schematic is rejected at load"
     }
     catch (const std::runtime_error& e)
     {
-        const std::string msg = e.what();
-        REQUIRE(msg.find("___does_not_exist___") != std::string::npos);
+        REQUIRE(std::string(e.what()).find("___nope___") != std::string::npos);
     }
 }
 
-TEST_CASE("unlock_requires referencing a real schematic loads without error", "[config]")
+TEST_CASE("validateUnlocks rejects an id granted by two groups", "[config]")
 {
     TempConfigDir dir;
     copyConfigInto(dir.path());
 
-    // "interceptor" is a ship schematic in the test config — a valid prerequisite.
-    std::ofstream out((dir.path() / "recipes.toml").string(), std::ios::app);
-    out << "\n[[recipe]]\n"
-           "id = \"gated_ok\"\n"
-           "building = \"assembler\"\n"
-           "unlock_at_station_level = 1\n"
-           "unlock_requires = [\"interceptor\"]\n"
-           "inputs = []\n"
-           "outputs = [{item = \"circuit_board\", amount = 1}]\n"
-           "duration_seconds = 1.0\n";
+    // repair_ship is already granted by the test config's unlocks.toml.
+    std::ofstream out((dir.path() / "unlocks.toml").string(), std::ios::app);
+    out << "\n[[unlock]]\nid = \"dup\"\nstation_level = 0\nships = [\"repair_ship\"]\n";
+    out.close();
+
+    try
+    {
+        ConfigLoader::loadFromDirectory(dir.path().string());
+        FAIL("Expected exception");
+    }
+    catch (const std::runtime_error& e)
+    {
+        REQUIRE(std::string(e.what()).find("already granted") != std::string::npos);
+    }
+}
+
+TEST_CASE("validateUnlocks rejects a non-assembler recipe grant", "[config]")
+{
+    TempConfigDir dir;
+    copyConfigInto(dir.path());
+
+    // mine_iron_ore is a miner recipe, not an assembler recipe.
+    std::ofstream out((dir.path() / "unlocks.toml").string(), std::ios::app);
+    out << "\n[[unlock]]\nid = \"badrecipe\"\nstation_level = 0\nrecipes = [\"mine_iron_ore\"]\n";
+    out.close();
+
+    try
+    {
+        ConfigLoader::loadFromDirectory(dir.path().string());
+        FAIL("Expected exception");
+    }
+    catch (const std::runtime_error& e)
+    {
+        REQUIRE(std::string(e.what()).find("mine_iron_ore") != std::string::npos);
+    }
+}
+
+TEST_CASE("validateUnlocks rejects requires naming an unknown group", "[config]")
+{
+    TempConfigDir dir;
+    copyConfigInto(dir.path());
+
+    std::ofstream out((dir.path() / "unlocks.toml").string(), std::ios::app);
+    out << "\n[[unlock]]\nid = \"needsmissing\"\nstation_level = 0\n"
+           "requires = [\"___missing___\"]\nships = [\"interceptor\"]\n";
+    out.close();
+
+    try
+    {
+        ConfigLoader::loadFromDirectory(dir.path().string());
+        FAIL("Expected exception");
+    }
+    catch (const std::runtime_error& e)
+    {
+        REQUIRE(std::string(e.what()).find("___missing___") != std::string::npos);
+    }
+}
+
+TEST_CASE("validateUnlocks rejects a group that grants nothing", "[config]")
+{
+    TempConfigDir dir;
+    copyConfigInto(dir.path());
+
+    std::ofstream out((dir.path() / "unlocks.toml").string(), std::ios::app);
+    out << "\n[[unlock]]\nid = \"empty\"\nstation_level = 0\n";
+    out.close();
+
+    try
+    {
+        ConfigLoader::loadFromDirectory(dir.path().string());
+        FAIL("Expected exception");
+    }
+    catch (const std::runtime_error& e)
+    {
+        REQUIRE(std::string(e.what()).find("grants no items") != std::string::npos);
+    }
+}
+
+TEST_CASE("validateUnlocks accepts a well-formed unlock group", "[config]")
+{
+    TempConfigDir dir;
+    copyConfigInto(dir.path());
+
+    // salvage_ship starts unlocked (not granted elsewhere); repair_ship is an
+    // existing group id, so this new group is valid.
+    std::ofstream out((dir.path() / "unlocks.toml").string(), std::ios::app);
+    out << "\n[[unlock]]\nid = \"extra\"\nstation_level = 2\n"
+           "requires = [\"repair_ship\"]\nships = [\"salvage_ship\"]\n";
     out.close();
 
     REQUIRE_NOTHROW(ConfigLoader::loadFromDirectory(dir.path().string()));

src/test/DeterminismTest.cpp

@@ -22,7 +22,7 @@ GameConfig loadConfig()
 constexpr int kScriptTicks = 2000;
 
 // Runs a fixed scripted session and returns the full-state checksum after every
-// tick. The script places a small factory, demolishes part of it mid-run, and
+// tick. The script places a small factory, deconstructs part of it mid-run, and
 // otherwise lets waves/combat run so the RNG stream and ECS state are exercised.
 std::vector<std::uint64_t> runScriptedSession(unsigned int seed)
 {
@@ -40,7 +40,7 @@ std::vector<std::uint64_t> runScriptedSession(unsigned int seed)
     {
         if (t == 500)
         {
-            // Demolish the second belt mid-run to exercise the removal paths.
+            // Deconstruct the second belt mid-run to exercise the removal paths.
             SimulationTestAccess::place(sim, BuildingType::Smelter, QPoint(-3, 3), Rotation::East);
         }
 

src/test/RecipeSchematicTest.cpp

@@ -57,36 +57,36 @@ static bool awaitRecipeUnlock(Simulation& sim, const std::string& recipeId,
 }
 
 // ---------------------------------------------------------------------------
-// ConfigLoader: parsing unlock_at_station_level on assembler recipes
+// ConfigLoader: unlocked_at_start and unlock-group gating on assembler recipes
 // ---------------------------------------------------------------------------
 
-TEST_CASE("RecipeSchematic: unlock_at_station_level = -1 parsed correctly", "[recipe_schematic]")
+TEST_CASE("RecipeSchematic: unlocked_at_start = true parsed correctly", "[recipe_schematic]")
 {
     const GameConfig cfg = loadConfig();
     const auto it = std::find_if(cfg.recipes.recipes.begin(), cfg.recipes.recipes.end(),
         [](const RecipeDef& r) { return r.id == "premium_circuit"; });
     REQUIRE(it != cfg.recipes.recipes.end());
-    REQUIRE(it->unlockAtStationLevel.has_value());
-    CHECK(it->unlockAtStationLevel.value() == -1);
+    CHECK(it->unlockedAtStart);
 }
 
-TEST_CASE("RecipeSchematic: unlock_at_station_level = 0 parsed correctly", "[recipe_schematic]")
+TEST_CASE("RecipeSchematic: a gated recipe is granted by an unlock group", "[recipe_schematic]")
 {
     const GameConfig cfg = loadConfig();
-    const auto it = std::find_if(cfg.recipes.recipes.begin(), cfg.recipes.recipes.end(),
-        [](const RecipeDef& r) { return r.id == "quick_circuit"; });
-    REQUIRE(it != cfg.recipes.recipes.end());
-    REQUIRE(it->unlockAtStationLevel.has_value());
-    CHECK(it->unlockAtStationLevel.value() == 0);
+    const bool granted = std::any_of(cfg.unlocks.groups.begin(), cfg.unlocks.groups.end(),
+        [](const UnlockGroupDef& g)
+        {
+            return std::find(g.recipes.begin(), g.recipes.end(), "quick_circuit") != g.recipes.end();
+        });
+    CHECK(granted);
 }
 
-TEST_CASE("RecipeSchematic: assembler recipe without the key has nullopt", "[recipe_schematic]")
+TEST_CASE("RecipeSchematic: an untagged assembler recipe has unlocked_at_start = false", "[recipe_schematic]")
 {
     const GameConfig cfg = loadConfig();
     const auto it = std::find_if(cfg.recipes.recipes.begin(), cfg.recipes.recipes.end(),
         [](const RecipeDef& r) { return r.id == "circuit_board"; });
     REQUIRE(it != cfg.recipes.recipes.end());
-    CHECK_FALSE(it->unlockAtStationLevel.has_value());
+    CHECK_FALSE(it->unlockedAtStart);
 }
 
 // ---------------------------------------------------------------------------
@@ -180,11 +180,11 @@ TEST_CASE("RecipeSchematic: eligible recipe schematic is eventually awarded on s
     REQUIRE(awaitRecipeUnlock(sim, "quick_circuit"));
 }
 
-TEST_CASE("RecipeSchematic: recipe whose output is not implicitly unlocked is never awarded",
+TEST_CASE("RecipeSchematic: an implicitly-gated recipe with no unlock group is never awarded",
           "[recipe_schematic]")
 {
-    // exotic_alloy produces exotic_alloy (not implicitly unlocked), so the
-    // output-unlocked guard must keep it out of the drop pool at every level.
+    // exotic_alloy is in no unlock group and its output/inputs are unreachable
+    // via the item graph, so it can never be dropped or implicitly unlocked.
     Simulation sim(loadConfig());
     for (int i = 0; i < 50; ++i)
     {
@@ -241,11 +241,11 @@ TEST_CASE("RecipeSchematic: recipe schematic can appear in pending choices",
         {
             for (const SchematicChoiceOption& opt : sim.getPendingSchematicChoices())
             {
-                if (opt.type == SchematicType::Recipe)
+                for (const GrantedSchematic& grant : opt.grantedItems)
                 {
-                    foundRecipeChoice = true;
-                    break;
+                    if (grant.type == SchematicType::Recipe) { foundRecipeChoice = true; break; }
                 }
+                if (foundRecipeChoice) { break; }
             }
             SimulationTestAccess::applySchematicChoice(sim, 0);
         }
@@ -377,11 +377,14 @@ TEST_CASE("SchematicDrop: an owned ship schematic is never offered again",
         const std::vector<SchematicChoiceOption>& choices =
             sim.getPendingSchematicChoices();
 
-        // Locate the repair_ship option, if present in this drop.
+        // Locate the option granting repair_ship, if present in this drop.
         int repairShipIndex = -1;
         for (int j = 0; j < static_cast<int>(choices.size()); ++j)
         {
-            if (choices[j].schematicId == "repair_ship") { repairShipIndex = j; }
+            for (const GrantedSchematic& grant : choices[j].grantedItems)
+            {
+                if (grant.id == "repair_ship") { repairShipIndex = j; break; }
+            }
         }
 
         // Once owned, it must never appear in the pool again.

src/test/ReplayPlaybackTest.cpp

@@ -77,12 +77,12 @@ TEST_CASE("parseCommand round-trips every command verb", "[replay]")
     ClearBeltTilesCommand clear;
     clear.tiles = { QPoint(0, 0), QPoint(-1, 4) };
 
-    DemolishCommand demolish;
-    demolish.id = 5;
+    DeconstructCommand deconstruct;
+    deconstruct.id = 5;
 
     for (const Command* command : { static_cast<const Command*>(&filters),
                                     static_cast<const Command*>(&clear),
-                                    static_cast<const Command*>(&demolish) })
+                                    static_cast<const Command*>(&deconstruct) })
     {
         const std::string text = serializeCommand(*command);
         const std::shared_ptr<Command> parsed = parseCommand(text);

src/test/ReplayRecorderTest.cpp

@@ -83,11 +83,11 @@ TEST_CASE("serializeCommand: splitter filters are length-prefixed", "[replay]")
             == "splitterfilters 4 7 2 iron_ore copper_ore 1 coal");
 }
 
-TEST_CASE("serializeCommand: demolish / rotate / schematic / clearbelt", "[replay]")
+TEST_CASE("serializeCommand: deconstruct / rotate / schematic / clearbelt", "[replay]")
 {
-    DemolishCommand demolish;
-    demolish.id = 12;
-    REQUIRE(serializeCommand(demolish) == "demolish 12");
+    DeconstructCommand deconstruct;
+    deconstruct.id = 12;
+    REQUIRE(serializeCommand(deconstruct) == "deconstruct 12");
 
     RotateInPlaceCommand rotate;
     rotate.id          = 7;

src/test/ShipyardTest.cpp

@@ -1,5 +1,7 @@
 #include "catch.hpp"
 
+#include <algorithm>
+
 #include "Building.h"
 #include "BuildingSystem.h"
 #include "BuildingType.h"
@@ -20,11 +22,24 @@ static GameConfig loadConfig()
     return ConfigLoader::loadFromDirectory(CONFIG_DIR);
 }
 
+// A ship starts unlocked iff no unlock group grants it (REQ-LOCK-EXPLICIT).
+static bool startsUnlocked(const GameConfig& cfg, const std::string& shipId)
+{
+    for (const UnlockGroupDef& group : cfg.unlocks.groups)
+    {
+        if (std::find(group.ships.begin(), group.ships.end(), shipId) != group.ships.end())
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
 static const ShipDef* findAvailableSchematic(const GameConfig& cfg)
 {
     for (const ShipDef& def : cfg.ships.ships)
     {
-        if (def.unlockAtStationLevel == -1 && !def.schematic.materials.empty())
+        if (startsUnlocked(cfg, def.id) && !def.schematic.materials.empty())
         {
             return &def;
         }

src/test/SimulationTestAccess.h

@@ -33,7 +33,12 @@ struct SimulationTestAccess
         return sim.tryPlaceBuilding(type, anchor, rotation);
     }
 
-    static void demolish(Simulation& sim, BuildingId id) { sim.demolish(id); }
+    static void deconstruct(Simulation& sim, BuildingId id) { sim.deconstruct(id); }
+
+    static void cancelDeconstruction(Simulation& sim, BuildingId id)
+    {
+        sim.cancelDeconstruction(id);
+    }
 
     static void applySchematicChoice(Simulation& sim, int choiceIndex)
     {

src/test/UnlockGroupTest.cpp

@@ -0,0 +1,117 @@
+// Unlock groups as the unit of loot (REQ-LOCK-EXPLICIT, REQ-LOCK-BUILDING,
+// REQ-DEF-SCHEMATIC-DROP): buildings can be locked, and one drop can grant a
+// building and a module together.
+
+#include <algorithm>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "catch.hpp"
+
+#include "BuildingType.h"
+#include "ConfigLoader.h"
+#include "FactionComponent.h"
+#include "GameConfig.h"
+#include "HealthComponent.h"
+#include "SchematicChoiceOption.h"
+#include "Simulation.h"
+#include "SimulationTestAccess.h"
+#include "StationBodyComponent.h"
+#include "UnlocksConfig.h"
+
+namespace
+{
+
+GameConfig loadConfig()
+{
+    return ConfigLoader::loadFromDirectory(CONFIG_DIR);
+}
+
+void killEnemyStations(Simulation& sim)
+{
+    sim.getAdmin().forEach<StationBodyComponent, FactionComponent, HealthComponent>(
+        [](entt::entity, StationBodyComponent&, FactionComponent& faction, HealthComponent& health)
+        {
+            if (faction.isEnemy) { health.hp = 0.0f; }
+        });
+    sim.tick();
+}
+
+// A config whose only unlock group grants the salvager module and the salvage
+// bay together, gated to the given station level.
+GameConfig configWithSalvageGroup(int stationLevel)
+{
+    GameConfig cfg = loadConfig();
+    cfg.unlocks.groups.clear();
+    cfg.unlocks.groups.push_back(
+        UnlockGroupDef{"salvage_operations", stationLevel, {}, {}, {"salvager"}, {"salvage_bay"}, {}});
+    return cfg;
+}
+
+} // namespace
+
+TEST_CASE("UnlockGroup: a building granted by a group is locked at game start", "[unlock_group]")
+{
+    const Simulation sim(configWithSalvageGroup(0));
+    CHECK_FALSE(sim.isBuildingUnlocked(BuildingType::SalvageBay));
+    CHECK_FALSE(sim.isModuleSchematicUnlocked("salvager"));
+    // A building in no unlock group is available from the start.
+    CHECK(sim.isBuildingUnlocked(BuildingType::Miner));
+}
+
+TEST_CASE("UnlockGroup: the drop option lists every granted item", "[unlock_group]")
+{
+    Simulation sim(configWithSalvageGroup(0));
+    killEnemyStations(sim);  // level 0
+    REQUIRE(sim.hasSchematicChoicesPending());
+
+    const std::vector<SchematicChoiceOption>& options = sim.getPendingSchematicChoices();
+    const auto it = std::find_if(options.begin(), options.end(),
+        [](const SchematicChoiceOption& o) { return o.unlockGroupId == "salvage_operations"; });
+    REQUIRE(it != options.end());
+
+    const bool grantsModule = std::any_of(it->grantedItems.begin(), it->grantedItems.end(),
+        [](const GrantedSchematic& g) { return g.type == SchematicType::Module && g.id == "salvager"; });
+    const bool grantsBuilding = std::any_of(it->grantedItems.begin(), it->grantedItems.end(),
+        [](const GrantedSchematic& g) { return g.type == SchematicType::Building && g.id == "salvage_bay"; });
+    CHECK(grantsModule);
+    CHECK(grantsBuilding);
+}
+
+TEST_CASE("UnlockGroup: awarding a group unlocks the building and module at once", "[unlock_group]")
+{
+    Simulation sim(configWithSalvageGroup(0));
+    killEnemyStations(sim);  // level 0
+    REQUIRE(sim.hasSchematicChoicesPending());
+
+    // The only eligible group is salvage_operations, so option 0 grants it.
+    REQUIRE(sim.getPendingSchematicChoices()[0].unlockGroupId == "salvage_operations");
+    SimulationTestAccess::applySchematicChoice(sim, 0);
+
+    CHECK(sim.isBuildingUnlocked(BuildingType::SalvageBay));
+    CHECK(sim.isModuleSchematicUnlocked("salvager"));
+}
+
+TEST_CASE("UnlockGroup: a group above the destroyed station level is not offered", "[unlock_group]")
+{
+    Simulation sim(configWithSalvageGroup(5));  // eligible only at level >= 5
+    killEnemyStations(sim);                      // level 0 push
+    // Pool is empty at level 0, so no choice dialog opens at all.
+    CHECK_FALSE(sim.hasSchematicChoicesPending());
+    CHECK_FALSE(sim.isBuildingUnlocked(BuildingType::SalvageBay));
+}
+
+TEST_CASE("UnlockGroup: reset re-locks a previously awarded building", "[unlock_group]")
+{
+    Simulation sim(configWithSalvageGroup(0));
+    killEnemyStations(sim);
+    REQUIRE(sim.getPendingSchematicChoices()[0].unlockGroupId == "salvage_operations");
+    SimulationTestAccess::applySchematicChoice(sim, 0);
+    REQUIRE(sim.isBuildingUnlocked(BuildingType::SalvageBay));
+
+    sim.reset();
+
+    CHECK_FALSE(sim.isBuildingUnlocked(BuildingType::SalvageBay));
+    CHECK_FALSE(sim.isModuleSchematicUnlocked("salvager"));
+}

src/test/UnlockPrereqTest.cpp

@@ -1,10 +1,10 @@
-// Drop-pool behaviour for unlock_requires schematic prerequisites
-// (REQ-LOCK-PREREQ). A schematic enters the drop pool only when every id in its
-// unlock_requires is already explicitly unlocked, on top of the station-level
-// (and, for recipes, output-implicitly-unlocked) checks.
+// Drop-pool behaviour for unlock-group prerequisites (REQ-LOCK-PREREQ). An
+// unlock group enters the drop pool only when every id in its `requires` names a
+// group that has already been awarded, on top of the station-level check.
 //
-// Configs are built in memory (load the test config, then mutate) so each case
-// is isolated and does not perturb the shared test config used by other suites.
+// Configs are built in memory (load the test config, then mutate the unlock
+// groups) so each case is isolated and does not perturb the shared test config
+// used by other suites.
 
 #include <algorithm>
 #include <string>
@@ -17,13 +17,11 @@
 #include "FactionComponent.h"
 #include "GameConfig.h"
 #include "HealthComponent.h"
-#include "ModulesConfig.h"
-#include "RecipesConfig.h"
 #include "SchematicChoiceOption.h"
-#include "ShipsConfig.h"
 #include "Simulation.h"
 #include "SimulationTestAccess.h"
 #include "StationBodyComponent.h"
+#include "UnlocksConfig.h"
 
 namespace
 {
@@ -33,34 +31,14 @@ GameConfig loadConfig()
     return ConfigLoader::loadFromDirectory(CONFIG_DIR);
 }
 
-ShipDef& findShip(GameConfig& cfg, const std::string& id)
+UnlockGroupDef& findGroup(GameConfig& cfg, const std::string& id)
 {
-    for (ShipDef& def : cfg.ships.ships)
+    for (UnlockGroupDef& group : cfg.unlocks.groups)
     {
-        if (def.id == id) { return def; }
+        if (group.id == id) { return group; }
     }
-    FAIL("ship not found: " + id);
-    return cfg.ships.ships.front();
-}
-
-ModuleDef& findModule(GameConfig& cfg, const std::string& id)
-{
-    for (ModuleDef& def : cfg.modules.modules)
-    {
-        if (def.id == id) { return def; }
-    }
-    FAIL("module not found: " + id);
-    return cfg.modules.modules.front();
-}
-
-RecipeDef& findRecipe(GameConfig& cfg, const std::string& id)
-{
-    for (RecipeDef& def : cfg.recipes.recipes)
-    {
-        if (def.id == id) { return def; }
-    }
-    FAIL("recipe not found: " + id);
-    return cfg.recipes.recipes.front();
+    FAIL("unlock group not found: " + id);
+    return cfg.unlocks.groups.front();
 }
 
 // Zeros the HP of both enemy defence stations and advances one tick so that
@@ -87,23 +65,28 @@ void killEnemyStationsAndApply(Simulation& sim)
     }
 }
 
+// True if any pending option grants the given schematic id.
 bool optionOffered(const Simulation& sim, const std::string& id)
 {
     const std::vector<SchematicChoiceOption>& options = sim.getPendingSchematicChoices();
     return std::any_of(options.begin(), options.end(),
-        [&](const SchematicChoiceOption& o) { return o.schematicId == id; });
+        [&](const SchematicChoiceOption& option)
+        {
+            return std::any_of(option.grantedItems.begin(), option.grantedItems.end(),
+                [&](const GrantedSchematic& grant) { return grant.id == id; });
+        });
 }
 
 } // namespace
 
-TEST_CASE("UnlockPrereq: a recipe gated behind a locked ship is withheld from the pool",
+TEST_CASE("UnlockPrereq: a group gated behind a locked ship is withheld from the pool",
           "[unlock_prereq]")
 {
-    // quick_circuit (assembler recipe, level 0, output circuit_board is implicitly
-    // unlocked) would normally be eligible at the first station destruction. Gate
-    // it behind repair_ship (ship, level 0, locked at game start).
+    // quick_circuit (recipe group, level 0) would normally be eligible at the
+    // first station destruction. Gate it behind the repair_ship group (level 0,
+    // locked at game start).
     GameConfig cfg = loadConfig();
-    findRecipe(cfg, "quick_circuit").unlockRequires = {"repair_ship"};
+    findGroup(cfg, "quick_circuit").requiredGroupIds = {"repair_ship"};
 
     Simulation sim(std::move(cfg), 123);
     REQUIRE_FALSE(sim.isSchematicUnlocked("repair_ship"));
@@ -111,22 +94,22 @@ TEST_CASE("UnlockPrereq: a recipe gated behind a locked ship is withheld from th
     killEnemyStations(sim);  // destroyed set level 0
     REQUIRE(sim.hasSchematicChoicesPending());
 
-    // Prerequisite unmet -> the gated recipe must not be offered, while the
-    // prerequisite schematic itself (the only other eligible pick) is.
+    // Prerequisite unmet -> the gated group must not be offered, while the
+    // prerequisite group itself (the only other eligible pick) is.
     CHECK_FALSE(optionOffered(sim, "quick_circuit"));
     CHECK(optionOffered(sim, "repair_ship"));
 }
 
-TEST_CASE("UnlockPrereq: the gated recipe becomes eligible once its prerequisite is unlocked",
+TEST_CASE("UnlockPrereq: the gated group becomes eligible once its prerequisite is awarded",
           "[unlock_prereq]")
 {
     GameConfig cfg = loadConfig();
-    findRecipe(cfg, "quick_circuit").unlockRequires = {"repair_ship"};
+    findGroup(cfg, "quick_circuit").requiredGroupIds = {"repair_ship"};
 
     Simulation sim(std::move(cfg), 123);
 
     // Applying choice 0 each drop unlocks repair_ship first (the only eligible
-    // pick at level 0), which then opens quick_circuit for a later drop.
+    // pick at level 0), which then opens the quick_circuit group for a later drop.
     bool unlocked = false;
     for (int i = 0; i < 150 && !unlocked; ++i)
     {
@@ -138,16 +121,16 @@ TEST_CASE("UnlockPrereq: the gated recipe becomes eligible once its prerequisite
     CHECK(unlocked);
 }
 
-TEST_CASE("UnlockPrereq: a module gated behind another module is withheld until it unlocks",
+TEST_CASE("UnlockPrereq: a module group gated behind another module is withheld until it unlocks",
           "[unlock_prereq]")
 {
-    // Mirror the app-config demo (laser_cannon_m -> laser_cannon_l) using two
-    // test-config modules made lockable at the same station level.
+    // Make laser_cannon and armor_plate (both start-unlocked in the test config)
+    // lockable via new unlock groups, with armor_plate gated behind laser_cannon.
     GameConfig cfg = loadConfig();
-    findModule(cfg, "laser_cannon").unlockAtStationLevel = 0;
-    ModuleDef& armor = findModule(cfg, "armor_plate");
-    armor.unlockAtStationLevel = 0;
-    armor.unlockRequires = {"laser_cannon"};
+    cfg.unlocks.groups.push_back(
+        UnlockGroupDef{"laser_cannon", 0, {}, {}, {"laser_cannon"}, {}, {}});
+    cfg.unlocks.groups.push_back(
+        UnlockGroupDef{"armor_plate", 0, {"laser_cannon"}, {}, {"armor_plate"}, {}, {}});
 
     Simulation sim(std::move(cfg), 7);
     REQUIRE_FALSE(sim.isModuleSchematicUnlocked("laser_cannon"));

src/test/WaveSystemTest.cpp

@@ -305,26 +305,35 @@ TEST_CASE("WaveSystem: push schematic choices have valid ids", "[wave]")
 
     for (const SchematicChoiceOption& opt : choices)
     {
-        bool validId = false;
-        for (const ShipDef& def : sim.getConfig().ships.ships)
+        if (opt.isArtifact) { continue; }
+        bool validGroup = false;
+        for (const UnlockGroupDef& group : sim.getConfig().unlocks.groups)
         {
-            if (def.id == opt.schematicId) { validId = true; break; }
+            if (group.id == opt.unlockGroupId) { validGroup = true; break; }
         }
-        if (!validId)
+        REQUIRE(validGroup);
+        // Every granted item must resolve to a defined ship/module/building/recipe.
+        for (const GrantedSchematic& grant : opt.grantedItems)
         {
+            bool validId = false;
+            for (const ShipDef& def : sim.getConfig().ships.ships)
+            {
+                if (def.id == grant.id) { validId = true; break; }
+            }
             for (const ModuleDef& def : sim.getConfig().modules.modules)
             {
-                if (def.id == opt.schematicId) { validId = true; break; }
+                if (def.id == grant.id) { validId = true; break; }
+            }
+            for (const BuildingDef& def : sim.getConfig().buildings.buildings)
+            {
+                if (def.id == grant.id) { validId = true; break; }
             }
-        }
-        if (!validId)
-        {
             for (const RecipeDef& def : sim.getConfig().recipes.recipes)
             {
-                if (def.id == opt.schematicId) { validId = true; break; }
+                if (def.id == grant.id) { validId = true; break; }
             }
+            REQUIRE(validId);
         }
-        REQUIRE(validId);
     }
 }
 
@@ -343,7 +352,7 @@ TEST_CASE("WaveSystem: schematic choices have no duplicates", "[wave]")
     std::set<std::string> ids;
     for (const SchematicChoiceOption& opt : choices)
     {
-        ids.insert(opt.schematicId);
+        ids.insert(opt.isArtifact ? std::string("<artifact>") : opt.unlockGroupId);
     }
     REQUIRE(ids.size() == choices.size());
 }

src/ui/BuildButtonGrid.cpp

@@ -2,23 +2,81 @@
 
 #include <string>
 
+#include <QByteArray>
+#include <QFile>
 #include <QGridLayout>
+#include <QIcon>
+#include <QPainter>
+#include <QPixmap>
 #include <QPushButton>
+#include <QRegularExpression>
 #include <QSignalMapper>
+#include <QSize>
+#include <QString>
+#include <QSvgRenderer>
 
 #include "BuildingType.h"
 #include "BuildingTypeSelectedEvent.h"
-#include "DemolishModeToggleRequestedEvent.h"
+#include "DeconstructModeToggleRequestedEvent.h"
 #include "DisplayName.h"
 #include "EventManager.h"
 #include "ExitBuilderModeRequestedEvent.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);
 
-BuildButtonGrid::BuildButtonGrid(Simulation* sim, const GameConfig* config, QWidget* parent)
+    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;
+    }
+}
+
+
+BuildButtonGrid::BuildButtonGrid(Simulation* sim, const GameConfig* config,
+                                 const std::string& iconDir, QWidget* parent)
     : QWidget(parent)
     , m_sim(sim)
     , m_config(config)
+    , m_iconDir(iconDir)
 {
     QGridLayout* layout = new QGridLayout(this);
     layout->setSpacing(4);
@@ -53,6 +111,12 @@ BuildButtonGrid::BuildButtonGrid(Simulation* sim, const GameConfig* config, QWid
         QPushButton* btn = new QPushButton(label, this);
         btn->setCheckable(true);
         btn->setFixedHeight(48);
+        // 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";
+        btn->setIcon(loadBuildingIcon(iconPath));
+        btn->setIconSize(kIconSize);
         if (def.tooltip)
         {
             btn->setToolTip(QString::fromStdString(*def.tooltip));
@@ -73,15 +137,19 @@ BuildButtonGrid::BuildButtonGrid(Simulation* sim, const GameConfig* config, QWid
     }
     connect(mapper, qOverload<int>(&QSignalMapper::mapped), this, &BuildButtonGrid::onBuildButton);
 
-    m_demolishButton = new QPushButton(tr("Demolish"), this);
-    m_demolishButton->setCheckable(true);
-    m_demolishButton->setFixedHeight(48);
-    layout->addWidget(m_demolishButton, row, col);
-    connect(m_demolishButton, &QPushButton::clicked, this, [this]() {
+    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);
+    layout->addWidget(m_deconstructButton, row, col);
+    connect(m_deconstructButton, &QPushButton::clicked, this, [this]() {
         EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<DemolishModeToggleRequestedEvent>());
+            std::make_shared<DeconstructModeToggleRequestedEvent>());
     });
 
+    updateVisibility();
     registerForEvents();
 }
 
@@ -119,6 +187,17 @@ void BuildButtonGrid::updateAffordability()
     }
 }
 
+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)
@@ -165,9 +244,15 @@ void BuildButtonGrid::handleEvent(std::shared_ptr<const BuildingBlocksChangedEve
     updateAffordability();
 }
 
-void BuildButtonGrid::handleEvent(std::shared_ptr<const DemolishModeChangedEvent> event)
+void BuildButtonGrid::handleEvent(std::shared_ptr<const UnlockedBuildingsChangedEvent> /*event*/)
 {
-    m_demolishButton->setChecked(event->active);
+    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)
@@ -176,9 +261,10 @@ void BuildButtonGrid::handleEvent(std::shared_ptr<const BuildHotkeyPressedEvent>
     {
         if (m_types[i] == event->type)
         {
-            // Equivalent to clicking the build button: a disabled (unaffordable)
-            // button cannot be clicked, so the hotkey is likewise inert.
-            if (m_buttons[i]->isEnabled())
+            // 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));
             }

src/ui/BuildButtonGrid.h

@@ -2,6 +2,7 @@
 
 #include <map>
 #include <optional>
+#include <string>
 #include <vector>
 
 #include <QWidget>
@@ -10,23 +11,28 @@
 #include "BuildHotkeyPressedEvent.h"
 #include "BuildingBlocksChangedEvent.h"
 #include "BuildingType.h"
-#include "DemolishModeChangedEvent.h"
+#include "DeconstructModeChangedEvent.h"
 #include "EventHandler.h"
 #include "GameConfig.h"
+#include "UnlockedBuildingsChangedEvent.h"
 
 class QPushButton;
 class Simulation;
 
 class BuildButtonGrid : public QWidget,
                         public CombinedEventHandler<BuilderModeExitedEvent,
-                                                    DemolishModeChangedEvent,
+                                                    DeconstructModeChangedEvent,
                                                     BuildHotkeyPressedEvent,
-                                                    BuildingBlocksChangedEvent>
+                                                    BuildingBlocksChangedEvent,
+                                                    UnlockedBuildingsChangedEvent>
 {
     Q_OBJECT
 
 public:
-    BuildButtonGrid(Simulation* sim, const GameConfig* config, QWidget* parent = nullptr);
+    // 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.
+    BuildButtonGrid(Simulation* sim, const GameConfig* config,
+                    const std::string& iconDir, QWidget* parent = nullptr);
     ~BuildButtonGrid() override;
 
     void clearActiveButton();
@@ -37,10 +43,15 @@ private:
     // 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 DemolishModeChangedEvent> 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);
@@ -48,9 +59,10 @@ private slots:
 private:
     Simulation*                      m_sim;
     const GameConfig*                m_config;
+    std::string                      m_iconDir;
     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_demolishButton;
+    QPushButton*                     m_deconstructButton;
 };

src/ui/GameWorldView.cpp

@@ -35,7 +35,7 @@
 #include "ReplayPlayer.h"
 #include "ReplayReader.h"
 #include "ReplayRecorder.h"
-#include "DemolishModeChangedEvent.h"
+#include "DeconstructModeChangedEvent.h"
 #include "EntityHitTest.h"
 #include "EntitySelectionChangedEvent.h"
 #include "EventManager.h"
@@ -67,6 +67,7 @@
 #include "BuilderModeExitedEvent.h"
 #include "BlueprintModeExitedEvent.h"
 #include "BuildingBlocksChangedEvent.h"
+#include "UnlockedBuildingsChangedEvent.h"
 #include "ExpansionCostChangedEvent.h"
 #include "GameSpeedChangedEvent.h"
 #include "SchematicChoicesAvailableEvent.h"
@@ -156,7 +157,7 @@ GameWorldView::GameWorldView(Simulation* sim, const GameConfig* config,
     , m_ghostRotation(Rotation::East)
     , m_ghostValid(false)
     , m_dragging(false)
-    , m_demolishMode(false)
+    , m_deconstructMode(false)
     , m_debugDraw(false)
     , m_rng(std::random_device{}())
     , m_boxSelecting(false)
@@ -367,6 +368,20 @@ void GameWorldView::onFrame()
             EventManager::getInstance()->sendEventImmediately(
                 std::make_shared<BossWaveUpdatedEvent>(newBoss, newCountdown));
         }
+
+        // Unlocked building set changes only after a drop is applied or on Restart
+        // (REQ-LOCK-BUILDING); the build grid rebuilds its visible buttons.
+        int newUnlockedBuildingCount = 0;
+        for (const BuildingDef& def : m_sim->getConfig().buildings.buildings)
+        {
+            if (m_sim->isBuildingUnlocked(def.type)) { ++newUnlockedBuildingCount; }
+        }
+        if (newUnlockedBuildingCount != m_lastUnlockedBuildingCount)
+        {
+            m_lastUnlockedBuildingCount = newUnlockedBuildingCount;
+            EventManager::getInstance()->sendEventImmediately(
+                std::make_shared<UnlockedBuildingsChangedEvent>());
+        }
     }
 
     // Sim-state polls are input sources for the live game; in replay these are
@@ -448,7 +463,7 @@ void GameWorldView::paintGL()
     drawOverlays(painter);
     drawScreenSpace(painter);
     drawPauseBorder(painter);
-    drawDemolishBorder(painter);
+    drawDeconstructBorder(painter);
     drawReplayOverlay(painter);
 }
 
@@ -801,13 +816,18 @@ void GameWorldView::placeBlueprintAtTile(QPoint center)
 
     for (const BlueprintBuilding& bb : bp.buildings)
     {
+        // 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 (!isValidPlacement(bb.type, center + bb.offset, bb.rotation)) { return; }
     }
 
-    // Cost only applies to buildings that are genuinely new (not rotate-in-place).
+    // Cost only applies to buildings that are genuinely new (not rotate-in-place),
+    // and excludes locked building types (REQ-LOCK-UI-BLUEPRINT).
     int totalCost = 0;
     for (const BlueprintBuilding& bb : bp.buildings)
     {
+        if (!m_sim->isBuildingUnlocked(bb.type)) { continue; }
         if (m_sim->getBuildings().findRotateInPlaceTarget(
                 bb.type, center + bb.offset, bb.rotation).has_value())
         {
@@ -820,6 +840,7 @@ void GameWorldView::placeBlueprintAtTile(QPoint center)
 
     for (const BlueprintBuilding& bb : bp.buildings)
     {
+        if (!m_sim->isBuildingUnlocked(bb.type)) { continue; }
         const QPoint anchor = center + bb.offset;
         const std::optional<BuildingId> rotateTarget =
             m_sim->getBuildings().findRotateInPlaceTarget(bb.type, anchor, bb.rotation);
@@ -1946,6 +1967,9 @@ void GameWorldView::drawOverlays(QPainter& painter)
     {
         for (const BlueprintBuilding& bb : m_blueprintMode->buildings)
         {
+            // Locked building types are omitted from the blueprint (REQ-LOCK-BUILDING,
+            // REQ-LOCK-UI-BLUEPRINT), so they are not ghosted either.
+            if (!m_sim->isBuildingUnlocked(bb.type)) { continue; }
             const QPoint anchor = m_blueprintGhostTile + bb.offset;
             const bool   valid  = isValidPlacement(bb.type, anchor, bb.rotation);
             drawBuildingGhost(painter, bb.type, anchor, bb.rotation, valid,
@@ -1953,9 +1977,20 @@ void GameWorldView::drawOverlays(QPainter& painter)
         }
     }
 
-    // Demolish tint: while dragging a demolish box, tint every covered
-    // building/site (REQ-BLD-DEMOLISH-BOX); otherwise tint the hovered one.
-    if (m_demolishMode && m_boxSelecting)
+    // Queued for deconstruction: tint every building currently in the
+    // deconstruction queue, regardless of mode (REQ-BLD-DECON-QUEUE).
+    for (const Building& b : m_sim->getBuildings().getAllBuildings())
+    {
+        if (!b.queuedForDeconstruction) { continue; }
+        for (const QPoint& cell : b.bodyCells)
+        {
+            painter.fillRect(tileRect(cell), m_visuals->overlays.deconstructTint);
+        }
+    }
+
+    // Deconstruct tint: while dragging a deconstruct box, tint every covered
+    // building/site (REQ-BLD-DECONSTRUCT-BOX); otherwise tint the hovered one.
+    if (m_deconstructMode && m_boxSelecting)
     {
         for (BuildingId id : buildingsInBox(m_boxStartTile, m_boxCurrentTile))
         {
@@ -1969,19 +2004,19 @@ void GameWorldView::drawOverlays(QPainter& painter)
             {
                 for (const QPoint& cell : *cells)
                 {
-                    painter.fillRect(tileRect(cell), m_visuals->overlays.demolishTint);
+                    painter.fillRect(tileRect(cell), m_visuals->overlays.deconstructTint);
                 }
             }
         }
     }
-    else if (m_demolishMode && m_demolishHoverBuildingId.has_value())
+    else if (m_deconstructMode && m_deconstructHoverBuildingId.has_value())
     {
-        const Building* b = m_sim->getBuildings().findBuilding(*m_demolishHoverBuildingId);
+        const Building* b = m_sim->getBuildings().findBuilding(*m_deconstructHoverBuildingId);
         if (b)
         {
             for (const QPoint& cell : b->bodyCells)
             {
-                painter.fillRect(tileRect(cell), m_visuals->overlays.demolishTint);
+                painter.fillRect(tileRect(cell), m_visuals->overlays.deconstructTint);
             }
         }
     }
@@ -2089,11 +2124,11 @@ void GameWorldView::drawPauseBorder(QPainter& painter)
     drawVignetteBorder(painter, QColor(0, 0, 0, 128));   // 50% black at the edge
 }
 
-void GameWorldView::drawDemolishBorder(QPainter& painter)
+void GameWorldView::drawDeconstructBorder(QPainter& painter)
 {
-    if (!m_demolishMode) { return; }
-    // Reuse the demolish overlay color (with its configured alpha) as the edge color.
-    drawVignetteBorder(painter, m_visuals->overlays.demolishTint);
+    if (!m_deconstructMode) { return; }
+    // Reuse the deconstruct overlay color (with its configured alpha) as the edge color.
+    drawVignetteBorder(painter, m_visuals->overlays.deconstructTint);
 }
 
 void GameWorldView::drawVignetteBorder(QPainter& painter, const QColor& edgeColor)
@@ -2290,7 +2325,7 @@ void GameWorldView::keyPressEvent(QKeyEvent* event)
     case Qt::Key_Q:
         if (m_builderType.has_value())        { exitBuilderMode(); }
         else if (m_blueprintMode.has_value()) { exitBlueprintMode(); }
-        else                                  { toggleDemolishMode(); }
+        else                                  { toggleDeconstructMode(); }
         break;
     case Qt::Key_T:
         // Request a temporary blueprint from the current selection (REQ-UI-BLUEPRINT-TEMP).
@@ -2352,7 +2387,7 @@ void GameWorldView::mousePressEvent(QMouseEvent* event)
                 }
             }
             else if (m_blueprintMode.has_value()) { exitBlueprintMode(); }
-            else if (m_demolishMode)              { toggleDemolishMode(); }
+            else if (m_deconstructMode)              { toggleDeconstructMode(); }
             else if (event->modifiers() & Qt::ShiftModifier)
             {
                 // Shift + right-click copies a building's settings, but only in the
@@ -2389,10 +2424,10 @@ void GameWorldView::mousePressEvent(QMouseEvent* event)
     {
         placeBlueprintAtTile(tile);
     }
-    else if (m_demolishMode)
+    else if (m_deconstructMode)
     {
-        // Start a demolish box drag; a plain click resolves as a 1x1 box on
-        // release (REQ-BLD-DEMOLISH-CLICK, REQ-BLD-DEMOLISH-BOX).
+        // 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;
@@ -2566,9 +2601,9 @@ void GameWorldView::mouseMoveEvent(QMouseEvent* event)
     {
         m_blueprintGhostTile = tile;
     }
-    else if (m_demolishMode)
+    else if (m_deconstructMode)
     {
-        m_demolishHoverBuildingId = buildingAtTile(tile);
+        m_deconstructHoverBuildingId = buildingAtTile(tile);
         if (m_boxSelecting) { m_boxCurrentTile = tile; }
     }
     else if (m_boxSelecting)
@@ -2597,20 +2632,65 @@ void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
         const std::vector<BuildingId> boxIds =
             buildingsInBox(m_boxStartTile, m_boxCurrentTile);
 
-        if (m_demolishMode)
+        if (m_deconstructMode)
         {
-            // Demolish every covered building/site; the HQ is protected
-            // (REQ-BLD-DEMOLISH, REQ-BLD-DEMOLISH-BOX).
+            const BuildingSystem& buildings = m_sim->getBuildings();
+
+            // Split covered ids into construction sites (removed instantly) and
+            // operational deconstructible buildings (the HQ is protected; player
+            // defence stations are not Buildings and never appear in the box).
+            std::vector<BuildingId> sites;
+            std::vector<BuildingId> operational;
             for (BuildingId id : boxIds)
             {
-                const Building* b = m_sim->getBuildings().findBuilding(id);
-                if (b && b->type == BuildingType::Hq) { continue; }
-                std::shared_ptr<DemolishCommand> command =
-                    std::make_shared<DemolishCommand>();
+                if (const Building* b = buildings.findBuilding(id))
+                {
+                    if (b->type == BuildingType::Hq) { continue; }
+                    operational.push_back(id);
+                }
+                else if (buildings.findSite(id))
+                {
+                    sites.push_back(id);
+                }
+            }
+
+            // Sites: instant demolition with the full refund (REQ-BLD-DECONSTRUCT).
+            for (BuildingId id : sites)
+            {
+                std::shared_ptr<DeconstructCommand> command =
+                    std::make_shared<DeconstructCommand>();
                 command->id = id;
                 enqueueCommand(command);
             }
-            m_demolishHoverBuildingId = std::nullopt;
+
+            // Operational buildings: if every covered one is already queued,
+            // un-queue them all; otherwise queue each one not yet queued. A plain
+            // click is the one-element case, giving the queue/un-queue toggle
+            // (REQ-BLD-DECONSTRUCT-BOX, REQ-BLD-DECONSTRUCT-CLICK).
+            bool allQueued = !operational.empty();
+            for (BuildingId id : operational)
+            {
+                if (!buildings.isQueuedForDeconstruction(id)) { allQueued = false; break; }
+            }
+            for (BuildingId id : operational)
+            {
+                if (allQueued)
+                {
+                    std::shared_ptr<CancelDeconstructionCommand> command =
+                        std::make_shared<CancelDeconstructionCommand>();
+                    command->id = id;
+                    enqueueCommand(command);
+                }
+                else if (!buildings.isQueuedForDeconstruction(id))
+                {
+                    std::shared_ptr<DeconstructCommand> command =
+                        std::make_shared<DeconstructCommand>();
+                    command->id = id;
+                    enqueueCommand(command);
+                }
+            }
+
+            m_deconstructHoverBuildingId = std::nullopt;
             return;
         }
 
@@ -2706,21 +2786,21 @@ void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
 // Methods (formerly slots)
 // ---------------------------------------------------------------------------
 
-void GameWorldView::toggleDemolishMode()
+void GameWorldView::toggleDeconstructMode()
 {
-    if (m_demolishMode)
+    if (m_deconstructMode)
     {
-        m_demolishMode    = false;
-        m_demolishHoverBuildingId = std::nullopt;
+        m_deconstructMode    = false;
+        m_deconstructHoverBuildingId = std::nullopt;
     }
     else
     {
         if (m_builderType.has_value())        { exitBuilderMode(); }
         if (m_blueprintMode.has_value())      { exitBlueprintMode(); }
-        m_demolishMode = true;
+        m_deconstructMode = true;
     }
     EventManager::getInstance()->sendEventImmediately(
-        std::make_shared<DemolishModeChangedEvent>(m_demolishMode));
+        std::make_shared<DeconstructModeChangedEvent>(m_deconstructMode));
 }
 
 void GameWorldView::rotateGhost(bool clockwise)
@@ -2851,18 +2931,18 @@ void GameWorldView::enterBuilderMode(BuildingType type)
     m_ghostValid      = false;
     m_tunnelGhostType = BuildingType::TunnelEntry;
     m_tunnelPartnerTile.reset();
-    m_demolishMode  = false;
+    m_deconstructMode  = false;
     m_blueprintMode.reset();
     EventManager::getInstance()->sendEventImmediately(
-        std::make_shared<DemolishModeChangedEvent>(false));
+        std::make_shared<DeconstructModeChangedEvent>(false));
 }
 
 void GameWorldView::enterBlueprintMode(Blueprint blueprint)
 {
     if (m_builderType.has_value()) { exitBuilderMode(); }
-    m_demolishMode = false;
+    m_deconstructMode = false;
     EventManager::getInstance()->sendEventImmediately(
-        std::make_shared<DemolishModeChangedEvent>(false));
+        std::make_shared<DeconstructModeChangedEvent>(false));
     m_blueprintGhostTile = m_ghostTile;
     m_blueprintMode      = std::move(blueprint);
 }
@@ -2913,10 +2993,10 @@ void GameWorldView::resetForNewGame()
     m_schematicChoiceShown = false;
     m_ghostRotation    = Rotation::East;
     m_ghostValid       = false;
-    m_demolishMode     = false;
-    m_demolishHoverBuildingId  = std::nullopt;
+    m_deconstructMode     = false;
+    m_deconstructHoverBuildingId  = std::nullopt;
     EventManager::getInstance()->sendEventImmediately(
-        std::make_shared<DemolishModeChangedEvent>(false));
+        std::make_shared<DeconstructModeChangedEvent>(false));
     m_selectedBuildingIds.clear();
     clearEntitySelection();
     clearScrapSelection();
@@ -2992,9 +3072,9 @@ void GameWorldView::handleEvent(std::shared_ptr<const ExitBuilderModeRequestedEv
     exitBuilderMode();
 }
 
-void GameWorldView::handleEvent(std::shared_ptr<const DemolishModeToggleRequestedEvent> /*event*/)
+void GameWorldView::handleEvent(std::shared_ptr<const DeconstructModeToggleRequestedEvent> /*event*/)
 {
-    toggleDemolishMode();
+    toggleDeconstructMode();
 }
 
 void GameWorldView::handleEvent(std::shared_ptr<const BlueprintPlacementRequestedEvent> event)

src/ui/GameWorldView.h

@@ -23,8 +23,8 @@
 #include "BuildingType.h"
 #include "BuildingTypeSelectedEvent.h"
 #include "BuildingId.h"
-#include "DemolishModeChangedEvent.h"
-#include "DemolishModeToggleRequestedEvent.h"
+#include "DeconstructModeChangedEvent.h"
+#include "DeconstructModeToggleRequestedEvent.h"
 #include "EventHandler.h"
 #include "ExitBlueprintModeRequestedEvent.h"
 #include "ExitBuilderModeRequestedEvent.h"
@@ -66,7 +66,7 @@ class GameWorldView : public QOpenGLWidget,
                       public CombinedEventHandler<BeamFiredEvent,
                                                   BuildingTypeSelectedEvent,
                                                   ExitBuilderModeRequestedEvent,
-                                                  DemolishModeToggleRequestedEvent,
+                                                  DeconstructModeToggleRequestedEvent,
                                                   BlueprintPlacementRequestedEvent,
                                                   ExitBlueprintModeRequestedEvent,
                                                   SpeedChangeRequestedEvent,
@@ -102,7 +102,7 @@ private:
     void handleEvent(std::shared_ptr<const BeamFiredEvent> event) override;
     void handleEvent(std::shared_ptr<const BuildingTypeSelectedEvent> event) override;
     void handleEvent(std::shared_ptr<const ExitBuilderModeRequestedEvent> event) override;
-    void handleEvent(std::shared_ptr<const DemolishModeToggleRequestedEvent> event) override;
+    void handleEvent(std::shared_ptr<const DeconstructModeToggleRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const BlueprintPlacementRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const ExitBlueprintModeRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const SpeedChangeRequestedEvent> event) override;
@@ -139,11 +139,11 @@ private:
     // to make the paused state hard to miss: a black frame whose alpha fades from 50% at
     // the viewport edges to 0% toward the center.
     void drawPauseBorder(QPainter& painter);
-    // Vignette-style border shown while demolish mode is active (REQ-UI-DEMOLISH-BORDER),
-    // tinted with the demolish overlay color (including its configured alpha) from
+    // Vignette-style border shown while deconstruct mode is active (REQ-UI-DECONSTRUCT-BORDER),
+    // tinted with the deconstruct overlay color (including its configured alpha) from
     // visuals.toml instead of black.
-    void drawDemolishBorder(QPainter& painter);
-    // Shared drawing for the pause/demolish vignettes: a mitred picture-frame border
+    void drawDeconstructBorder(QPainter& painter);
+    // Shared drawing for the pause/deconstruct vignettes: a mitred picture-frame border
     // whose alpha fades from `edgeColor` (with its own alpha) at the viewport edge to
     // fully transparent toward the center.
     void drawVignetteBorder(QPainter& painter, const QColor& edgeColor);
@@ -252,7 +252,7 @@ private:
     void     exitBuilderMode();
     void     enterBlueprintMode(Blueprint blueprint);
     void     exitBlueprintMode();
-    void     toggleDemolishMode();
+    void     toggleDeconstructMode();
     void     rotateGhost(bool clockwise);
 
     struct ActiveBeam
@@ -328,8 +328,8 @@ private:
     std::vector<CopyConfigFlash> m_copyConfigFlashes;
     static constexpr qint64      kCopyFlashDurationMs = 300;
 
-    bool     m_demolishMode;
-    std::optional<BuildingId> m_demolishHoverBuildingId;
+    bool     m_deconstructMode;
+    std::optional<BuildingId> m_deconstructHoverBuildingId;
     bool     m_debugDraw;
 
     std::vector<BuildingId> m_selectedBuildingIds;
@@ -351,4 +351,5 @@ private:
     int  m_lastBossCounter   = -1;
     Tick m_lastBossCountdown = Tick(-1);
     int  m_lastArtifactCount = -1;
+    int  m_lastUnlockedBuildingCount = -1;
 };

src/ui/MainWindow.cpp

@@ -6,6 +6,7 @@
 
 #include <QApplication>
 #include <QCloseEvent>
+#include <QDir>
 #include <QFile>
 #include <QMessageBox>
 #include <QPushButton>
@@ -51,8 +52,13 @@ MainWindow::MainWindow(Simulation* sim, const std::string& configDir,
     sideLayout->setContentsMargins(1, 1, 1, 1);
     sideLayout->setSpacing(1);
 
+    // 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();
+
     m_selectedBuildingPanel = new SelectedBuildingPanel(sim, &sim->getConfig(), m_sidePanel);
-    m_buildButtonGrid       = new BuildButtonGrid(sim, &sim->getConfig(), m_sidePanel);
+    m_buildButtonGrid       = new BuildButtonGrid(sim, &sim->getConfig(), iconDir, m_sidePanel);
     m_blueprintPanel        = new BlueprintPanel(sim, &sim->getConfig(), m_sidePanel);
 
     sideLayout->addWidget(m_selectedBuildingPanel, 1);

src/ui/SchematicChoiceDialog.cpp

@@ -21,6 +21,18 @@ const RecipeDef* findRecipe(const RecipesConfig& recipes, const std::string& id)
     return nullptr;
 }
 
+QString grantKindLabel(SchematicType type)
+{
+    switch (type)
+    {
+    case SchematicType::Ship:     return SchematicChoiceDialog::tr("Ship");
+    case SchematicType::Module:   return SchematicChoiceDialog::tr("Module");
+    case SchematicType::Building: return SchematicChoiceDialog::tr("Building");
+    case SchematicType::Recipe:   return SchematicChoiceDialog::tr("Recipe");
+    }
+    return QString();
+}
+
 }  // namespace
 
 SchematicChoiceDialog::SchematicChoiceDialog(
@@ -63,7 +75,7 @@ SchematicChoiceDialog::SchematicChoiceDialog(
         nameLabel->setAlignment(Qt::AlignCenter);
         cardLayout->addWidget(nameLabel);
 
-        if (option.type == SchematicType::Artifact)
+        if (option.isArtifact)
         {
             QLabel* artifactTypeLabel = new QLabel(tr("Artifact"), card);
             artifactTypeLabel->setAlignment(Qt::AlignCenter);
@@ -71,22 +83,22 @@ SchematicChoiceDialog::SchematicChoiceDialog(
         }
         else
         {
-            QString typeText;
-            if (option.type == SchematicType::Ship)
+            QLabel* grantsHeaderLabel = new QLabel(tr("Unlocks:"), card);
+            QFont grantsHeaderFont = grantsHeaderLabel->font();
+            grantsHeaderFont.setBold(true);
+            grantsHeaderLabel->setFont(grantsHeaderFont);
+            grantsHeaderLabel->setAlignment(Qt::AlignCenter);
+            cardLayout->addWidget(grantsHeaderLabel);
+
+            for (const GrantedSchematic& grant : option.grantedItems)
             {
-                typeText = tr("Ship");
+                QLabel* grantLabel = new QLabel(
+                    grantKindLabel(grant.type) + ": "
+                        + QString::fromStdString(grant.displayName),
+                    card);
+                grantLabel->setAlignment(Qt::AlignCenter);
+                cardLayout->addWidget(grantLabel);
             }
-            else if (option.type == SchematicType::Module)
-            {
-                typeText = tr("Module");
-            }
-            else
-            {
-                typeText = tr("Recipe");
-            }
-            QLabel* typeLabel = new QLabel(typeText, card);
-            typeLabel->setAlignment(Qt::AlignCenter);
-            cardLayout->addWidget(typeLabel);
 
             QLabel* unlocksHeaderLabel = new QLabel(tr("Unlocks recipes:"), card);
             QFont unlocksHeaderFont = unlocksHeaderLabel->font();

src/ui/VisualsConfig.h

@@ -44,7 +44,7 @@ struct OverlayVisuals
 {
     QColor ghostValid;
     QColor ghostInvalid;
-    QColor demolishTint;
+    QColor deconstructTint;
     QColor selectionRect;
     QColor tileHighlight;
     QColor selectedOutline;

src/ui/VisualsLoader.cpp

@@ -220,7 +220,7 @@ VisualsConfig VisualsLoader::load(const std::string& path)
         toml::table& ov = requireSubtable(tbl, "overlays", "root");
         cfg.overlays.ghostValid      = parseColor(requireString(ov, "ghost_valid",      "overlays"), "overlays.ghost_valid");
         cfg.overlays.ghostInvalid    = parseColor(requireString(ov, "ghost_invalid",    "overlays"), "overlays.ghost_invalid");
-        cfg.overlays.demolishTint    = parseColor(requireString(ov, "demolish_tint",    "overlays"), "overlays.demolish_tint");
+        cfg.overlays.deconstructTint    = parseColor(requireString(ov, "deconstruct_tint",    "overlays"), "overlays.deconstruct_tint");
         cfg.overlays.selectionRect   = parseColor(requireString(ov, "selection_rect",   "overlays"), "overlays.selection_rect");
         cfg.overlays.tileHighlight   = parseColor(requireString(ov, "tile_highlight",   "overlays"), "overlays.tile_highlight");
         cfg.overlays.selectedOutline = parseColor(requireString(ov, "selected_outline", "overlays"), "overlays.selected_outline");