Chessistics/PLAN.md

Chessistics — Prototype Roadmap

Phase 1: Core solvability (DONE)

• Black Box Sim pattern: commands self-apply via DoApply()/AssertApplicationConditions()
• 3 piece types: Rook (orthogonal range 2), Bishop (diagonal range 2), Knight (L-jump)
• Relay chain mechanic with shared relay points (collision-free alternating)
• Transfer system: production → pieces → demands, 4-adjacency, participation tracking
• Victory/defeat: all demands met vs deadline expired

Phase 2: Cargo-type aware transfers (DONE)

• CargoFilter property on PieceState: optional CargoType? restricting accepted cargo
• Auto-assigned at placement via relay chain tracing (adjacency to production, then shared relay points with filtered pieces)
• TransferResolver enforces filter: receivers with mismatched CargoFilter are skipped
• Forward-direction sorting uses cargo-type-aware MinDistanceToProduction to avoid wrong sorting when multiple productions exist
• Level 3 restored to dual-cargo (Wood+Stone) with 10R+2K stock
• GDD stock corrections: Level 2 = 6R+1B, Level 3 = 10R+2K
• 60 tests passing including 2 new CargoFilter tests

Phase 3: Surplus stock and puzzle difficulty tuning

Goal: Levels give more pieces than the minimum, creating genuine puzzle space.

• With forward-preferring transfers working, longer chains are viable.
• Design levels where the player has choice: multiple valid solutions with different efficiency scores (PiecesUsed, TurnsTaken, CellsOccupied).
• Add scoring/star system based on Metrics.
• Levels 4-6: increasing board size (8x8, 10x10), more complex wall layouts, multiple productions and demands.

Phase 4: New piece — Pion (Pawn)

Goal: Add a one-directional piece for asymmetric relay constraints.

• Pion moves forward only (one direction, range 1).
• Cheap to place (low piece cost if scoring is added).
• Creates interesting constraints: must plan direction of cargo flow.
• Test levels specifically designed around Pion usage.

Phase 5: Network levels and Dame (Queen)

Goal: Open-ended logistics puzzles with interconnected supply networks.

• Multiple productions feeding multiple demands through shared infrastructure.
• Dame piece: combines Rook + Bishop movement (range 2, all 8 directions).
• Powerful but expensive — forces cost/benefit tradeoffs.
• Larger boards (12x12+) with complex wall configurations.
• Potential for player-designed levels (level editor data format).

Phase 6: Godot integration

Goal: Playable visual prototype.

• Board renderer: grid, walls, buildings, pieces.
• Drag-and-drop piece placement during Edit phase.
• Step/play/pause simulation controls.
• Event visualization: cargo movement, transfers, delivery animations.
• Victory/defeat screens with Metrics display.