This is Finessimo — a small game that helps you master “2‑step finesse”: placing any tetromino with the minimum inputs. The goal is durable muscle memory first; speed follows naturally. For new players learning block stacking games, getting used to finesse movements early can be useful to avoid having to re-learn muscle memory later.

If you want the deep dive, see DESIGN.md (architecture) and FILES.md (map).

• Prereqs: Node.js 18+, npm
• Install: npm install
• Dev server (HMR): npm run dev → opens http://localhost:3000

• npm run typecheck — TypeScript only (no emit)
• npm run lint — Lint (fixes enabled by default in local dev)
• npm run test — Jest unit tests
• One‑shot all checks: npm run check (clean → typecheck → lint → test:coverage → format)

Other handy scripts 🛠️

• npm run build — Production build (Vite)
• npm run test:watch / npm run test:coverage

The architecture is functional, deterministic, and types‑first.

• Flow: UI → Input Handler → Reducer → State → UI
• Core: Pure reducer with immutable GameState (discriminated union). Branded primitives keep look‑alike types from mixing.
• Input: A Robot3‑powered DAS/ARR state machine drives movement; handlers dispatch pure Actions and append normalized ProcessedAction entries for finesse analysis.
• Pipeline: After a piece locks, a pure lock pipeline runs finesse analysis and asks the active mode whether to commit or retry.
• Determinism: Seeded 7‑bag via PieceRandomGenerator; modes can own RNG/preview.
• Reactivity: @lit-labs/signals exposes gameStateSignal + selectors for minimal UI work.

• src/app/app.ts — App loop, wiring, lock pipeline, mode switching, settings bridge.
• src/app/settings.ts — Load/save settings to localStorage (merged nested store).
• src/state/types.ts — Brands, GameState union, Action union, ProcessedAction, stats.
• src/state/reducer.ts — Pure reducer; physics post‑step integration; pending‑lock seam; derived stats.
• src/state/signals.ts — Global signal + selectors + reducer‑backed dispatch.
• src/input/keyboard/handler.ts — Keyboard over DAS/ARR; logging rules.
• src/input/touch/handler.ts — Touch overlay/gestures over shared DAS.
• src/input/machines/das.ts — Robot3 DAS machine (idle → charging → repeating).
• src/engine/finesse/* — Board‑aware BFS calculator, pure service, processed‑log helpers.
• src/modes/* — Mode contracts/registry (FreePlay, Guided), RNG/preview/guidance hooks, lock decisions.
• src/core/* — Board ops, SRS rotation, RNGs (core/rng/*), spawning/top‑out.
• src/ui/components/* — Lit components (board, overlays, settings, panels).
• src/ui/renderers/* — Pure canvas renderers (cells/overlays/grid/tween/viewport).
• src/types/* — Branded primitives (DurationMs, GridCoord, Seed, …) and Timestamp utilities.

• Purity: Side‑effects only at the edges (input, DOM/time, storage, audio). Core stays pure.
• Types‑first: Encode invariants with brands and discriminated unions. Use assertNever for exhaustiveness.
• Immutability: Never mutate in reducers; always return new objects/arrays.
• No suppressions: Don’t add @ts-ignore or ESLint disables — fix the types instead.
• Run the gates: npm run check before committing.

Apache-2.0