snake

A playable, browser-based Snake game with no build step — open index.html directly, or serve the folder with any static server.

This is the M1 + M2 deliverable of Radius Red's engineering-loop demo: a small four-agent team (build → review → test → docs) shipping real features through reviewed GitHub PRs. The full record of how each milestone was built — decisions, trade-offs, rejected alternatives — is in docs/milestones/1-playable-snake.md and docs/milestones/2-persistent-best-progressive-difficulty.md.

Run

No install, no build:

git clone https://github.com/radiusred/snake.git
cd snake

Then either open index.html directly in a browser (file://), or serve the folder with any trivial static server, e.g.:

python3 -m http.server

(npx http-server . also works, but the first run downloads and installs the http-server package and asks for interactive confirmation — not a "no install" option.)

Play

• Move — arrow keys, WASD, or a swipe on a touchscreen.
• Eat — steer the snake onto the red food cell; it grows by one segment and the score goes up by one. The game speeds up progressively as the score grows, down to a floor, so a session gets harder as it goes.
• Game over — hitting a wall or the snake's own body ends the run and shows the final score in an overlay.
• Restart — click the Restart button, press Space / Enter while the overlay is showing, or tap the button on a touchscreen.

The score bar tracks the current score and the best score, which persists across page reloads via localStorage. Directly reversing into the snake's own neck (e.g. pressing Down while moving Up, or swiping back the way you came) is ignored rather than ending the game.

Tests

npm test

Runs the full suite via node --test (no dependencies to install) — 46 tests:

• tests/game.test.js (13 tests) — pure game-logic unit tests: movement, growth and scoring, reversal rejection, wall/self collision, food never placed on the snake, the vacating-tail edge case, and the tickInterval progressive-difficulty curve (base, decreasing, floor, bad-input guarding).
• tests/bestscore.test.js (12 tests) — unit tests for the persisted-best store: empty store reads as 0, a stored integer round-trips, garbage and negative values (including a numeric-prefix-then-garbage string) read as 0, a new high is written, a lower score never overwrites a higher stored best, and a throwing storage is tolerated.
• tests/browser.test.js (21 tests) — dependency-free browser-integration tests: index.html/game.js served over a trivial static server, the page loading logic via a classic <script src> with no build markers, raw-source boot, live #score DOM updates, the game-over overlay with the exact final score, Restart resetting the DOM, a real ArrowUp keydown turning the snake, the best score surviving a simulated reload, the loop speeding up (and resetting on restart) as the score grows, and swipe gestures steering the snake alongside keyboard input.

How it's built

• index.html — the page: a <canvas> grid, the score-driven game loop, keyboard and touch/swipe input, the score bar, and the game-over overlay. The controller script lives inline in the page (not a separate file — see Decision 2 in the M1 milestone doc for why).
• game.js — pure, deterministic game logic (createState, step, setDirection, placeFood, tickInterval) with no DOM dependency. Loaded by the page via a plain <script src="game.js"> and shared verbatim with the test suite via require() — the same code runs in both (see Decision 1). tickInterval(score) maps the score to the loop's tick interval so the game speeds up progressively (see Decision 1 in the M2 milestone doc).
• bestscore.js — a pure, dependency-free module (loadBest, saveBest) over an injectable storage, defaulting to the browser's localStorage, that persists the best score across page reloads and degrades gracefully when storage is unavailable or throws.

License

See LICENSE.