add blueprint requirements

docs/requirements.md

@@ -60,7 +60,7 @@ Output port indicators are not building tiles themselves. A building may have mo
 - REQ-BLD-GHOST: While in builder mode, a ghost of the building is rendered at the tile under the cursor, showing where it would be placed.
 - REQ-BLD-ROTATE: While in builder mode, pressing E rotates the ghost 90° clockwise and Q 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.
-- 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 — and (b) no footprint cell overlaps an existing placed building or construction site. Affordability is not re-checked at placement time: builder mode cannot be entered when the player cannot afford the building (REQ-UI-BUILD-DISABLED), so once in builder mode the only placement validity concerns are terrain and overlap. The ghost (REQ-BLD-GHOST) is rendered in a distinct "invalid" color when the current cursor position fails either condition.
+- 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, and (c) the player has enough building blocks to afford the building. The ghost (REQ-BLD-GHOST) is rendered in a distinct "invalid" color when the current cursor position fails any of these conditions.
 - REQ-BLD-BELT-DRAG: For belts, the player can click and drag across multiple tiles to place a construction site on each tile in one gesture.
 - 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.
 
@@ -167,16 +167,17 @@ The screen is divided into three vertical sections:
 |                                                  |
 |               Game World (70%)                   |
 |                                                  |
-+-------------------------+------------------------+
++-----------------+-----------------+--------------+
-| Selected Building Panel | Build Button Grid      |
+| Selected        | Build Button    | Blueprint    |
-|         (left)          |       (right)          |
+| Building Panel  | Grid            | Panel        |
-+-------------------------+------------------------+
+|    (left)       |   (center)      |   (right)    |
++-----------------+-----------------+--------------+
 ```
 
 - REQ-UI-HEADER: The header bar spans the full width above the game world and always shows the elapsed survival time and the current global building blocks stock on the left, and game speed controls on the right.
 - REQ-UI-SPEED: The game speed controls in the header bar are buttons for 0×, 0.5×, 1×, 2×, and 4× 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-WORLD-HEIGHT: The game world view occupies 70% of the remaining screen height below the header bar.
-- REQ-UI-PANEL-HEIGHT: The UI panel occupies the remaining 30% of the screen height, split horizontally into a selected building panel (left) and a build button grid (right).
+- REQ-UI-PANEL-HEIGHT: The UI panel occupies the remaining 30% of the screen height, split horizontally into a selected building panel (left), a build button grid (center), and a blueprint panel (right).
 
 ### Game World
 
@@ -221,3 +222,19 @@ The screen is divided into three vertical sections:
 - REQ-UI-BUILD-COST: Each button caption shows the building name and its building block cost, e.g. "Belt: 2 Blocks".
 - 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 pressing Backspace (REQ-UI-HOTKEYS). The button is shown in a visually active/pressed state while demolish mode is active.
+
+### Blueprint Panel
+
+- REQ-UI-BLUEPRINT-PANEL: The blueprint panel is shown to the right of the build button grid. It contains, from top to bottom: a "Create Blueprint" button, a "Delete Blueprint" button, and a list of blueprint buttons (one per saved blueprint, in creation order).
+
+- REQ-UI-BLUEPRINT-CREATE: The "Create Blueprint" button is enabled only when one or more buildings are currently selected. 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 and appends its button to the blueprint list.
+
+- REQ-UI-BLUEPRINT-STORAGE: A blueprint stores its name and, for each building in the selection, the building type, its rotation, and its tile offset (integer dx, dy) from the center of the bounding box of all selected buildings' footprints. This structure maps directly to a TOML representation (e.g. one `[[building]]` array entry per constituent building).
+
+- REQ-UI-BLUEPRINT-BUTTON: Each 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.
+
+- 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). Pressing Q/E 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. 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 Blueprint" button toggles delete mode on and off. While delete mode is active the button is shown in a visually active/pressed state. Clicking any blueprint button while delete mode is active removes that blueprint from the list and automatically exits delete mode.