AFTERGLOW 🦄🌈

▶ Play it now — the exact 13 kB submission build, auto-deployed from main.

The storm swallowed the world's colors. Run, last unicorn — your afterglow brings them back.

A unicorn survivors-like in 13 kB, made for js13kGames 2026 (theme: Unicorns and Rainbows).

Your rainbow trail is your weapon: shadows that touch the afterglow burn away, standing still means zero firepower, and every field you cross blooms back to color.

How to play

• Move — WASD / arrow keys, drag anywhere (touch), or gamepad stick / d-pad
• Your afterglow trail damages shadows that touch it — keep galloping, it's your only weapon
• Collect shards to level up and pick 1 of 3 upgrades (click / keys 1–3 / gamepad)
• Elites (gold crown) drop luck items: magnet, bomb, rainbow rush, star shower, heart
• Heal the meadow — bloom milestones (25 / 50 / 75 / 100 %) drop bonus items
• M or the speaker icon toggles mute, the vertical bar below it sets volume, R = quick restart

Build

Requires Node ≥ 22. zip must be on PATH; advzip (advancecomp) is optional but squeezes out extra bytes.

npm ci
npm run build       # → dist/game.zip — fails if it exceeds 13,312 bytes
npm run build:max   # submission build (Roadroller -O2, slow)
npm run dev         # dev server at http://localhost:1313 with live reload

More commands:

command	what it does
npm run size	build + one-line size summary
npm run smoke	runs the built game in real Chromium/Firefox — asserts zero console errors
npm run playtest	automated end-to-end play session with assertions + screenshots
npm run lint	ESLint (flat config) over src/ and tools/
npm run typecheck	JSDoc-based tsc --strict
npm run check	lint + typecheck + build + smoke

Under the 13 kB hood

• Zero asset files — everything is procedural: vector-canvas art, ZzFX sound effects, and a WebAudio sequencer playing a hypnotic 6/8 Celtic lilt (composed against an AI-generated reference track, ported into code via FFT analysis)
• Fake-3D sky island — y-sorted draw order, cliff face, waterfalls and parallax clouds below
• One build, every device — unified pointer/keyboard/gamepad input abstraction and a responsive logical viewport serve desktop and mobile from the same zip
• Pipeline: esbuild → terser (3-pass, property mangling) → Roadroller → inline HTML → zip -9 → advzip -4 (zopfli). The terser-only and Roadroller candidates are compared by final zip size — Roadroller's high-entropy output can lose to plain terser after deflate
• Readable source — src/ stays commented and idiomatic; all compression lives in tools/build.mjs

Repository layout

src/
├── engine/   reusable core — fixed-timestep loop, responsive canvas, input, sfx, save
├── game/     the game — player, mobs, loot, stats, fx, music, orchestration
├── vendor/   ZzFXMicro (MIT, modified for lazy AudioContext)
└── main.js   entry point
tools/        build pipeline, dev server, smoke test, automated playtest
docs/         design notes and research

Credits

• ZzFXMicro v1.3.2 by Frank Force (MIT)
• Built for js13kGames — thirteen kilobytes, no excuses