Retroix 🕹️

A tiny, dependency-free retro game engine in a single file. Drop it in with a <script> tag — no build step, no npm required — and everything a small canvas game needs is there.

 

Retroix is a general-purpose 2D game engine for the browser. It bundles the plumbing every small game re-implements — a DPI-aware canvas, a crash-safe game loop, input, sound, physics, a camera, screens, leaderboards and more — so your game is just its own update(dt) / render(ctx) and level data. It ships as one UMD file (window.Retroix), works from a CDN or a bundler, and has zero dependencies.

A whole gallery of games is built on it — they're the showcase, not the point. It gives you:

• 🖥️ DPI-aware canvas — a fixed logical resolution scaled crisply to any size.
• 🔁 Render-safe game loop — requestAnimationFrame with a clamped delta; can't die mid-frame.
• ⌨️ Input — keyboard (arrows + WASD → named actions), mouse and touch in logical coords.
• 🔊 8-bit audio — synthesized on the Web Audio API, zero sample files: SFX presets (coin, jump, laser, explosion, powerup, hit…), short jingles, and custom tones, with persistent mute/volume.
• 🎵 Chiptune music — looping, multi-voice background tracks defined as data (no files): per-level tunes with crossfade, pause/resume, ducking under loud SFX, and an independent music volume under one master mute.
• 💥 Game feel — screen shake, flash, and freeze-frame (hitstop) to make hits land.
• 🧲 Arcade physics — gravity/friction/max-vel integration + axis-separated AABB resolution with onGround/blocked flags.
• 🗺️ Tile grid — cell↔world coords, and solids() that feeds collision rects straight into physics.
• 🎥 Camera — follow a target, clamp to level bounds, begin/end world transform.
• 🔀 State machine — title / play / pause / over with enter/update/exit hooks.
• ⏱️ Timers & tweens — after / every callbacks and eased property tweens.
• 📐 Collision — AABB / circle / circle-rect / point overlap tests.
• 💾 Storage — namespaced, JSON-friendly localStorage for best scores and settings.
• 🤖 Autopilot — a secret-combo dev mode that turns a bot loose to play your game unattended: checks it's finishable, and surfaces crashes and soft-locks with an on-screen report.
• 🏆 Leaderboard — Supabase REST with a localStorage fallback (top / submit / qualifies).
• 🪟 Screens — overlay manager, retro 3-initial high-score entry, and a leaderboard table renderer.
• ✨ gfx — roundRect, a particle-burst system, and a fading toast helper.
• 🎨 retroix.css — the neon-on-dark theme (HUD, buttons, screens, initials, leaderboard).

…so a game is just its own update(dt) / render(ctx) and level data.

Games built on Retroix

Seven full games run on the engine — each just a few hundred lines of game logic. They're the proving ground (and the fun part). ▶ Play them all in the live gallery.

Blastix · run-and-gun platformer	Paddix · brick-breaker
Alienix · twin-stick survivor	Space-Jam · side-scrolling shmup
BombJack · vertical road shooter	Castle · maze chase & rescue
Nimix · beach game of Nim

Install

No build step required. Load it straight from a CDN — it's a UMD file, so window.Retroix is available globally:

<link href="https://fonts.googleapis.com/css2?family=Press+Start+2P&display=swap" rel="stylesheet">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/retroix@1.2.0/retroix.css">
<script src="https://cdn.jsdelivr.net/npm/retroix@1.2.0/retroix.js"></script>

Or from the GitHub repo (no npm needed):

<script src="https://cdn.jsdelivr.net/gh/DanMat/Retroix@v1.2.0/retroix.js"></script>

Or with a bundler:

npm install retroix

import Retroix from 'retroix';
import 'retroix/css';

Quick start

<canvas id="game" width="480" height="640"></canvas>
<script>
  var view = Retroix.canvas('#game', 480, 640);   // dpr-aware
  var input = Retroix.input(view);                 // keyboard + pointer
  var board = Retroix.leaderboard({ gameId: 'demo' }); // local unless Supabase configured

  var x = 240, y = 320;
  Retroix.loop(function (dt) {
    var a = input.axis();
    x += a.x * 200 * dt; y += a.y * 200 * dt;
    var ctx = view.ctx;
    ctx.fillStyle = '#0a0a1c'; ctx.fillRect(0, 0, 480, 640);
    ctx.fillStyle = '#00e5ff'; Retroix.gfx.roundRect(ctx, x - 15, y - 15, 30, 30, 6); ctx.fill();
  }).start();
</script>

API

Call	What you get
Retroix.canvas(el, w, h)	{ ctx, width, height, dpr, resize(), toLogical(cx,cy) }
Retroix.loop(step, opts)	{ start(), stop(), isRunning() } — step(dt) in seconds
Retroix.input(canvas, opts)	{ actions, pointer, down(a), axis(), onKeyDown(fn) }
Retroix.audio(opts)	{ coin(), …, play(name), jingle(name), tone(spec), sequence(notes), music(track), stopMusic(), pauseMusic(), resumeMusic(), duck(), musicVolume(v), mute(v), volume(v), toggle() }
Retroix.tracks	built-in chiptune loops: title, action, boss, calm
Retroix.fx(dims, opts)	{ shake(a), flash(color,s), freeze(dur), frozen(), update(dt), preRender(ctx), postRender(ctx) }
Retroix.hit	rects(a,b), circles(a,b), circleRect(c,r), pointRect(px,py,r), pointCircle(px,py,c)
Retroix.physics	body(opts), move(body, solids, dt) — arcade integration + AABB resolution
Retroix.grid(cols, rows, tile)	{ at, set, cellAt, rectOf, forEach, solids(isSolid, region) }
Retroix.camera(view, opts)	{ x, y, follow(t,l), clamp(), begin(ctx), end(ctx), worldToScreen, screenToWorld }
Retroix.fsm(states, initial)	{ set(name,…), update(dt), render(ctx), is(name), current() }
Retroix.timer()	{ after(s,fn), every(s,fn), tween(obj,props,dur,ease,done), cancel(t), update(dt) }
Retroix.ease	linear, inQuad, outQuad, inOutQuad, inCubic, outCubic, outBack, outBounce
Retroix.storage(ns)	{ get(key,fallback), set(key,val), remove(key), keys(), clear() }
Retroix.autopilot(cfg)	secret-combo test bot (finishability / chokepoints) — { start(), stop(), running() }
Retroix.jumpReach(opts)	{ maxDist, maxHeight, airtimeFrames, apexFrames } from jump physics
Retroix.leaderboard(cfg)	{ top(n), submit(initials,score,stage), qualifies(score), mode }
Retroix.screens(root)	{ show(id), hideAll(), current() } over [data-screen] elements
Retroix.initials(el, {onEnter})	3-letter entry: { value(), reset(), handleKey(e), active }
Retroix.renderLeaderboard(tbody, rows, opts)	fills a <tbody> with score rows
Retroix.gfx	roundRect, particles()
Retroix.toast(el)	returns toast(msg, ms)
Retroix.util	clamp, rand, randInt, pick, hypot, dist2, lerp, shuffle, escapeHtml

8-bit audio

No files — every sound is synthesized. The first key/tap unlocks audio (browsers require a gesture); mute and volume persist across sessions.

var sfx = Retroix.audio();     // { volume: 0.35 } by default

sfx.coin();                    // built-in presets
sfx.explosion();
sfx.play('laser');             // …or by name
sfx.jingle('win');             // short stingers: win / lose / levelup / gameover
sfx.tone({ wave: 'square', freq: 'C5', freqEnd: 'C6', dur: 0.15 }); // custom blip
sfx.sequence(['C5:0.08', 'E5', 'G5']);   // your own melody

sfx.toggle();                  // mute button; sfx.volume(0.5) to set level

Autopilot (dev-mode test bot)

A secret key combo (the Konami code by default) turns a bot loose to play your game unattended — to check it's finishable and to surface crashes, soft-locks and impassable spots. The engine can't win your game, so supply a bot(api) policy + closures over your state. The recommended model: give the game infinite lives (respawn in place) and pass deaths() (a monotonic failure counter) + location(). The bot keeps trying; if it dies deathsPerSpot times within one spot, that's flagged an impassable chokepoint — with the coordinate to fix. A stuck-watchdog, timeout, isWin(), and crash capture round it out, and the report names the worst death hotspot. (No bot → a generic masher smoke-tests boot→play.)

Retroix.autopilot({
  start:    function () { testMode = true; if (state === 'title') startGame(); }, // infinite lives
  stop:     function () { testMode = false; },
  bot:      botDrive,                                    // uses grid/physics to jump gaps
  progress: function () { return levelIndex * 1e5 + player.x; },
  location: function () { return levelIndex * 1e5 + deathX; },  // where it last died
  deaths:   function () { return deathCount; },          // you bump this on each respawn
  isWin:    function () { return wonFlag; },
  deathsPerSpot: 6
});
// toggle with ↑ ↑ ↓ ↓ ← → ← → B A. api: press/release/tap/only, t, frame.

Pair it with a static reachability check so you catch impossible geometry without even running the bot:

var reach = Retroix.jumpReach({ jump: JUMP, gravity: GRAV, run: RUN });
// reach.maxDist — if a level gap is wider than this, the jump is impossible.

Chiptune background music

Tracks are data, not files — a tempo and a step grid per voice. Each token is one step: a note (C4, F#3), - for a rest, or . to hold the previous note one more step. Give each level its own tune; switching crossfades.

sfx.music('action');                 // a built-in loop from Retroix.tracks
sfx.music(level.track, { fade: 0.6 });   // …or your own, per level (crossfades)

sfx.pauseMusic();  sfx.resumeMusic();    // pause with the game
sfx.duck(0.4, 0.5);                      // dip music under a big hit (auto on explosion)
sfx.musicVolume(0.4);                    // music volume, independent of SFX
sfx.stopMusic(0.5);

// A track is just an object:
var boss = {
  tempo: 150, stepsPerBeat: 4,
  voices: [
    { wave: 'square',   vol: 0.26, notes: 'C5 C#5 C5 C#5 C5 - G5 - G#5 G5 G#5 G5 - - F5 -' },
    { wave: 'sawtooth', vol: 0.30, notes: 'C3 . C3 . C3 . C3 . G#2 . G#2 . G2 . G2 .' }
  ]
};

Game feel

var fx = Retroix.fx(view);     // pass the canvas api (or { width, height })

// on a big hit:
sfx.hit(); fx.shake(0.6); fx.flash('#fff', 0.4); fx.freeze(0.05);

// in the loop:
fx.update(dt);
if (!fx.frozen()) { updateWorld(dt); }   // hitstop pauses the world, not the loop
fx.preRender(ctx);                        // shake offset applied
drawWorld(ctx);
fx.postRender(ctx);                       // flash overlay drawn on top

Arcade physics + tile grid

Bodies integrate gravity/friction and resolve against static rects. A grid turns your level into those rects for free:

var grid = Retroix.grid(40, 30, 16);      // 40×30 tiles, 16px each
grid.set(5, 20, 1);                        // 1 = solid

var hero = Retroix.physics.body({ x: 80, y: 40, w: 12, h: 16, gravity: 0.6, friction: 0.2, maxVx: 4, maxVy: 12 });

Retroix.loop(function (dt) {
  var a = input.axis();
  hero.vx = a.x * 4;
  if (input.down('up') && hero.onGround) { hero.vy = -11; sfx.jump(); }

  var solids = grid.solids(null, { x: hero.x - 40, y: hero.y - 40, w: 120, h: 120 }); // only nearby tiles
  Retroix.physics.move(hero, solids, dt);
  // hero.onGround / hero.blocked.left|right|up|down are now set for this frame
}).start();

Cap velocity (maxVx/maxVy) below your tile size — arcade physics steps discretely, so an uncapped body can skip clean over a thin wall.

Camera, state machine & tweens

var cam = Retroix.camera(view, { bounds: { x: 0, y: 0, w: 640, h: 480 } });
cam.follow(hero, 0.1);                      // smooth follow
cam.begin(ctx); drawWorld(ctx); cam.end(ctx);

var game = Retroix.fsm({
  title: { enter: function () { showScreen('title'); } },
  play:  { update: function (dt) { stepWorld(dt); } },
  over:  { enter: function () { sfx.jingle('gameover'); } }
}, 'title');
// game.set('play'); game.update(dt); if (game.is('play')) { … }

var tm = Retroix.timer();
tm.tween(hero, { y: hero.y - 20 }, 0.3, 'outBack');   // little hop
tm.after(1.5, function () { game.set('over'); });
// in the loop: tm.update(dt);

Leaderboard config

Retroix.leaderboard({
  supabaseUrl: 'https://YOUR-PROJECT.supabase.co', // blank = local only
  supabaseAnonKey: 'sb_publishable_...',           // public by design
  gameId: 'paddix',
  size: 10
});

The Supabase board expects a scores table (game, initials, score, stage, created_at) protected by row-level-security. See any consuming game's docs/supabase.sql.

CSS

retroix.css styles .rx-* classes and reads CSS variables you can override (--rx-accent, --rx-pixel, --rx-panel, …) to reskin per game. Load the Press Start 2P font for the headings.

License

MIT © DanMat