3.1 KiB
pattern-placement Specification
Purpose
Lets users select a Game of Life pattern, preview it under the mouse cursor, rotate it, and place copies on the grid with a click.
Requirements
Requirement: Selecting a pattern arms a placement tool
The system SHALL activate a placement tool for the selected pattern when a select:<pattern> action is triggered, and show a preview following the cursor.
Scenario: Tool activation
- WHEN the user triggers
select:glider - THEN a glider preview appears at the current cursor position
- AND the placement tool remains active
Requirement: Preview follows cursor motion
The system SHALL update the preview position to track the current mouse cursor cell while a tool is active.
Scenario: Mouse moves
- WHEN the user moves the mouse while a tool is active
- THEN the preview moves to the cell under the cursor
Requirement: Tool can be rotated in 90-degree steps
The system SHALL rotate the active preview by 90 degrees each time the rotate action is triggered.
Scenario: Rotate preview
- WHEN the user triggers the rotate action while a tool is active
- THEN the preview rotates 90 degrees clockwise
- AND remains at the same anchor cell
Requirement: Left click places the pattern when valid
The system SHALL write the active pattern's alive cells into the grid at the preview position when the user left-clicks and the pattern fits entirely within the grid.
Scenario: Valid placement
- WHEN the user left-clicks while a tool is active and the preview fits in the grid
- THEN the pattern's cells become alive in the grid
- AND the tool remains active for further placement
Requirement: Invalid placement is rejected
The system SHALL not modify the grid when a left click occurs while the preview extends outside the grid.
Scenario: Out of bounds
- WHEN the user left-clicks while the preview extends outside the grid
- THEN no cells are changed
- AND the tool remains active
Requirement: Escape cancels the active tool
The system SHALL deactivate the placement tool and remove the preview when the cancel action is triggered.
Scenario: Cancel placement
- WHEN the user triggers the cancel action while a tool is active
- THEN the preview disappears
- AND no further clicks place a pattern until a tool is selected again
Requirement: Click without active tool does nothing
The system SHALL ignore left clicks when no placement tool is active.
Scenario: No tool
- WHEN the user left-clicks while no tool is active
- THEN the grid is unchanged
Requirement: Additional built-in patterns are available
The system SHALL provide additional built-in patterns (Beacon, Loaf, Boat, Tub, R-pentomino, Acorn) selectable via keys 5-0.
Scenario: Select beacon
- WHEN the user triggers
select:beacon - THEN a beacon preview is shown
Requirement: New patterns support rotation
The system SHALL support 90-degree rotation for all new patterns.
Scenario: Rotate new pattern
- WHEN the user rotates a new pattern preview
- THEN its cells rotate accordingly