# SNAKE — Xiaomi Watch S4

Textured Snake on a 16×16 grid: 20px tiles, 320px board, centered on a round
466px screen. Existing PNG board, directional snake pieces, apple and icon are
preserved. Package identity: `com.ilias.snake`.

**Version 0.7 (versionCode 7): locally tested and release-built; the new features
still need an on-watch check.** Earlier versions rendered and played on the
user's Watch S4 41mm. Node tests and numeric layout checks are not device tests.

## Play

- **Swipe** to steer. A two-turn queue accepts rapid corners, consumes one turn
  per tick, and rejects duplicate directions and reversals against the last
  queued direction. Excess inputs are ignored, not allowed to replace a turn.
- **Tap the board, snake or apple** to pause. Tap **RESUME** (or an exposed part
  of the board) to resume. Pausing clears queued turns.
- In the pause or game-over panel, select **CLASSIC** (walls end the run) or
  **WRAP** (cross an edge to appear on the opposite edge). Changing mode starts
  a fresh, paused game; tap RESUME to begin. Selecting the current mode does not
  reset the run. The current mode is shown below the board.
- Both modes end on self-collision. Moving into the vacating tail is legal.
- **PLAY AGAIN** is a large 216×56px retry target. Retry keeps the selected mode,
  resets score/speed/queued turns, and starts playing. Filling the board displays
  **YOU WIN** and hides the apple safely.
- Leaving the page pauses it and stops the timer. Returning requires an explicit
  resume; game-over never resumes automatically. The system back action remains
  untouched. No crown, rotary, side-button or back interception APIs are used.

## Score, speed and persistence

Each apple is one point. The always-visible header shows score and best. One
best score is shared across Classic and Wrap, saved through documented
[`@system.storage`](https://iot.mi.com/vela/quickapp/en/features/data/storage.html)
under `snake.best`. Mode is session-only; a newly created page defaults to Classic.

The movement interval starts at **300ms**, decreases by **10ms per apple**, and
never goes below **120ms**. Only one movement timer runs; none runs while hidden,
paused, finished or destroyed. Old timer callbacks are invalidated.

Storage reads merge with the in-memory maximum; writes wait for the initial
read and are serialized/coalesced so slow callbacks cannot overwrite a newer
record. The coordinator survives page recreation within the module lifetime.
Invalid saved values are ignored. Errors/exceptions do not interrupt gameplay:
failed reads/writes retry on later apples or page-show activity, without a retry
loop. A failed/uncompleted write or immediate app termination may lose the
unsaved record. Storage persistence still needs verification on the watch.

## Lightweight rendering

Directional PNG tiles use only `left`/`top` positioning, no transforms or new
art assets. Wrapped neighbors are normalized before classifying seam textures.
Food placement takes at most 256 cell checks, including a nearly full board.
The HUD, footer, board and overlay fit the circular chord numerically with
at least an 8px total horizontal safety allowance.

## Build and test

```bash
npm ci
npm test
npm run release
```

`npm test` runs the original core, piece and page tests, 13 incremental upgrade
regressions, the numeric layout suite, and deterministic randomized property tests. Upgrade coverage includes rapid
swipes, lifecycle/timer races, storage failures and async ordering, mode changes,
all four Wrap edges, seam textures, full-board victory and bounded food spawning.
New behaviors were exercised through failing-then-passing test cycles.

Release output: `dist/com.ilias.snake.release.0.7.rpk`. The locked
`aiot-toolkit` 2.0.5 uses the existing `sign/private.pem` and `sign/certificate.pem`;
do not regenerate or commit those keys. Release uses plain JS (not JSC/protobuf),
matching the previously working toolchain. The dependency lock is unchanged;
`npm ci` currently reports 14 development-toolchain audit findings (3 low,
11 high). No forced toolkit upgrade was applied.

## Files

- `src/pages/index/index.ux`: round-screen UI, swipe queue, game/lifecycle state.
- `src/common/snake.js`: movement, collision, Wrap piece classification, food.
- `src/common/best.js`: asynchronous storage coordinator.
- `src/common/tex/`: preserved textured artwork.
- `tests/{snake,pieces,page,upgrade,layout,properties}.cjs`: Node regression suites.

Install the signed RPK through AstroBox. Source/releases live at
https://gitea.oimcloud.myaddr.tools/codex-bot/vela-snake — publication is a
separate step after review; a local build is not evidence of a published release.

## Earlier versions

- 0.2/0.3: board played on watch; designWidth 480→466 fixed undersizing.
- 0.6: directional textured tiles and preserved user-supplied icon.
- 0.7: queued swipes, live/persisted records, capped acceleration, pause/resume,
  lifecycle safety, retry/win panels and selectable Classic/Wrap.