Sonic Unleashed Recompiled Explained: Build Your Own Speed Platformer

<!doctype html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><title>Skycoil Sprint — original speed-platformer example</title><link rel="stylesheet" href="game.css"><script type="module" src="main.mjs"></script></head><body><main><a href="/guides/sonic-unleashed-recompiled-build-speed-platformer">← Tutorial and complete source</a><h1>Skycoil Sprint</h1><p>Original 2D tutorial game. Run to the beacon; jump over red drones and collect teal energy cells. Concept artwork in the guide shows a possible future art direction.</p><canvas id="game" width="960" height="480" tabindex="0" aria-label="Skycoil Sprint game. A D or arrows move, Space jumps, Shift boosts."></canvas><p id="status" role="status" aria-live="polite">Ready. Press Start.</p><p id="hud">Lives 3 · Energy 100 · Cells 0 · Time 0</p><div class="menu"><button id="start">Start / Resume</button><button id="pause">Pause</button><button id="restart">Restart</button></div><div class="controls" aria-label="Touch controls"><button data-key="left" aria-label="Hold to move left">◀</button><button data-key="right" aria-label="Hold to move right">▶</button><button data-key="jump">JUMP</button><button data-key="boost">BOOST</button></div><label><input id="sound" type="checkbox"> Enable short sound effects</label><p>A/D or arrows · Space to jump · Shift to boost · P to pause. Leaving the tab pauses the game. Restart makes a fresh run; your local best is separate.</p><p id="best">No saved local best yet.</p><p><a href="README.md">Run, test and publish this example</a> · <a href="LICENSE.txt">MIT licence</a></p></main></body></html>

// Original, independently written public tutorial. MIT, 2026 BINX Forge.
export const WIDTH=960,HEIGHT=480,GOAL=2260;
export const platforms=[{x:0,y:404,w:620,h:76},{x:620,y:372,w:480,h:108},{x:1100,y:404,w:440,h:76},{x:1540,y:350,w:450,h:130},{x:1990,y:404,w:410,h:76}];
export const hazards=[{x:440,y:380,w:34,h:24},{x:930,y:348,w:34,h:24},{x:1430,y:380,w:34,h:24},{x:1810,y:326,w:34,h:24}];
const overlap=(a,b)=>a.x<b.x+b.w&&a.x+a.w>b.x&&a.y<b.y+b.h&&a.y+a.h>b.y;
export function fresh(){return {status:'ready',time:0,lives:3,energy:100,cells:0,player:{x:70,y:368,w:24,h:36,vx:0,vy:0,grounded:true},checkpoint:70,collected:[],camera:0,coyote:.1,buffer:0,jumpHeld:false,immune:0,message:'Reach the wind beacon. Jump over red drones; collect teal cells.'};}
export function start(s){if(s.status==='ready'||s.status==='paused')s.status='running';}
export function pause(s){if(s.status==='running'){s.status='paused';s.jumpHeld=false;s.buffer=0;}}
export function damage(s){if(s.status!=='running'||s.immune>0)return;s.lives--;if(s.lives<=0){s.status='lost';s.message='Out of lives. Restart the route.';return;}const p=s.player;p.x=s.checkpoint;p.y=s.checkpoint<1000?368:368;p.vx=p.vy=0;p.grounded=false;s.immune=1.4;s.energy=Math.max(s.energy,35);s.message='Checkpoint recovered. Your collected cells are safe.';}
function tick(s,input,dt){
 const p=s.player;s.time+=dt;if(s.time>=60){s.time=60;s.status='lost';s.message='Time expired. Try a cleaner route.';return;}
 s.immune=Math.max(0,s.immune-dt);s.buffer=Math.max(0,s.buffer-dt);s.coyote=p.grounded?.1:Math.max(0,s.coyote-dt);
 const dir=Number(!!input.right)-Number(!!input.left),boost=!!input.boost&&dir!==0&&s.energy>0;
 s.energy=Math.max(0,Math.min(100,s.energy+(boost?-38:16)*dt));
 const target=dir*(boost?460:260),rate=dir?1400:1700;p.vx+=Math.max(-rate*dt,Math.min(rate*dt,target-p.vx));
 if(s.buffer>0&&s.coyote>0){p.vy=-570;p.grounded=false;s.coyote=0;s.buffer=0;}
 if(!input.jump&&p.vy<-260)p.vy=-260;
 p.vy=Math.min(820,p.vy+1500*dt);const oldBottom=p.y+p.h;
 p.x=Math.max(0,Math.min(2370,p.x+p.vx*dt));
 for(const q of platforms){if(overlap(p,q)){if(p.vx>0)p.x=q.x-p.w;else if(p.vx<0)p.x=q.x+q.w;p.vx=0;}}
 p.y+=p.vy*dt;p.grounded=false;
 for(const q of platforms){if(overlap(p,q)){if(p.vy>=0&&oldBottom<=q.y+2){p.y=q.y-p.h;p.vy=0;p.grounded=true;}else if(p.vy<0){p.y=q.y+q.h;p.vy=0;}}}
 for(let i=0;i<12;i++){const c={x:200+i*165,y:(i>=3&&i<=5?280:i>=9&&i<=10?260:316),w:20,h:20};if(!s.collected.includes(i)&&overlap(p,c)){s.collected.push(i);s.cells++;s.energy=Math.min(100,s.energy+24);}}
 if(p.x>=1140&&p.grounded)s.checkpoint=1140;
 if(p.y>HEIGHT+100||hazards.some(h=>overlap(p,h)))damage(s);
 if(p.x>=GOAL&&s.status==='running'){s.status='won';s.message='Delivery complete! '+s.cells+' energy cells, '+s.time.toFixed(2)+' seconds.';}
 s.camera=Math.max(0,Math.min(1440,p.x-280));
}
export function advance(s,input={},elapsed=0){if(s.status!=='running'||!Number.isFinite(elapsed)||elapsed<=0)return;const rising=!!input.jump&&!s.jumpHeld;s.jumpHeld=!!input.jump;if(rising)s.buffer=.13;let left=Math.min(elapsed,.1);for(let i=0;i<12&&left>1e-9&&s.status==='running';i++){const dt=Math.min(left,1/120);tick(s,input,dt);left-=dt;}}
export function readBest(raw){try{const s=JSON.parse(raw);return s?.version===1&&Number.isFinite(s.best)&&s.best>0&&s.best<=60&&Number.isInteger(s.cells)&&s.cells>=0&&s.cells<=12?{version:1,best:s.best,cells:s.cells}:null;}catch{return null;}}

import {WIDTH,HEIGHT,platforms,hazards,GOAL} from './world.mjs';
export function render(ctx,s,{reduced=false}={}){
 ctx.clearRect(0,0,WIDTH,HEIGHT);const bg=ctx.createLinearGradient(0,0,0,HEIGHT);bg.addColorStop(0,'#123649');bg.addColorStop(1,'#377e80');ctx.fillStyle=bg;ctx.fillRect(0,0,WIDTH,HEIGHT);
 for(let i=0;i<8;i++){const x=i*180-s.camera*.22;ctx.fillStyle=i%2?'#215364':'#296577';ctx.beginPath();ctx.moveTo(x,420);ctx.lineTo(x+90,170+(i%3)*38);ctx.lineTo(x+190,420);ctx.fill();}
 ctx.save();ctx.translate(-s.camera,0);
 for(const q of platforms){ctx.fillStyle='#173840';ctx.fillRect(q.x,q.y,q.w,q.h);ctx.fillStyle='#67b58c';ctx.fillRect(q.x,q.y,q.w,10);for(let i=0;i<q.w;i+=50){ctx.fillStyle='#244b51';ctx.fillRect(q.x+i+12,q.y+30,25,28);}}
 for(let i=0;i<12;i++){if(s.collected.includes(i))continue;const x=210+i*165,y=(i>=3&&i<=5?290:i>=9&&i<=10?270:326);ctx.fillStyle='#6dfff0';ctx.beginPath();for(let j=0;j<6;j++){const a=j*Math.PI/3;ctx.lineTo(x+12*Math.cos(a),y+12*Math.sin(a));}ctx.closePath();ctx.fill();}
 for(const h of hazards){ctx.fillStyle='#fd7977';ctx.fillRect(h.x,h.y,h.w,h.h);ctx.fillStyle='#271e35';ctx.fillRect(h.x+5,h.y+7,7,7);ctx.fillRect(h.x+22,h.y+7,7,7);}
 ctx.fillStyle='#fbc86e';ctx.fillRect(1140,318,6,86);ctx.fillRect(1146,318,50,26);ctx.fillStyle='#83ffdf';ctx.fillRect(GOAL+20,280,8,124);ctx.beginPath();ctx.arc(GOAL+24,272,24,0,Math.PI*2);ctx.fill();
 const p=s.player,phase=reduced?0:Math.sin(s.time*22)*(p.grounded?Math.min(1,Math.abs(p.vx)/260):.3);ctx.save();ctx.translate(p.x+p.w/2,p.y+p.h/2);if(s.immune>0&&!reduced&&Math.floor(s.time*12)%2)ctx.globalAlpha=.45;
 ctx.fillStyle='#ffb958';ctx.fillRect(-9,-6,18,21);ctx.fillStyle='#f6d7b0';ctx.fillRect(-7,-19,14,14);ctx.fillStyle='#1d2933';ctx.fillRect(-8,-20,17,5);ctx.fillStyle='#ff754b';ctx.fillRect(-10,-4,25,5);ctx.fillRect(-22,-4+(reduced?0:phase*2),18,4);ctx.fillStyle='#6bffe8';ctx.fillRect(-9,14,7,7+phase*4);ctx.fillRect(3,14,7,7-phase*4);ctx.restore();ctx.restore();
 ctx.fillStyle='rgba(5,20,29,.85)';ctx.fillRect(18,18,325,70);ctx.fillStyle='#e5fff7';ctx.font='bold 18px sans-serif';ctx.fillText('SKYCOIL SPRINT',32,44);ctx.font='14px sans-serif';ctx.fillText('Energy '+Math.round(s.energy)+' • Cells '+s.cells+' • Lives '+s.lives,32,72);
 if(s.status!=='running'){ctx.fillStyle='rgba(3,15,24,.72)';ctx.fillRect(0,HEIGHT/2-42,WIDTH,84);ctx.fillStyle='#fff5dd';ctx.textAlign='center';ctx.font='bold 25px sans-serif';ctx.fillText(s.status==='ready'?'Ready for a wind-run?':s.status==='paused'?'Paused':s.status==='won'?'Delivery complete!':'Try again',WIDTH/2,HEIGHT/2+8);ctx.textAlign='left';}
}

import {fresh,start,pause,advance,readBest} from './world.mjs';
import {render} from './render.mjs';
const canvas=document.getElementById('game'),ctx=canvas.getContext('2d'),status=document.getElementById('status'),hud=document.getElementById('hud'),bestNode=document.getElementById('best'),sound=document.getElementById('sound'),motion=matchMedia('(prefers-reduced-motion: reduce)');
let state=fresh(),last=0,audio=null,saved=false;const keyboard=new Set(),pointers=new Map(),keyMap={ArrowLeft:'left',KeyA:'left',ArrowRight:'right',KeyD:'right',Space:'jump',ShiftLeft:'boost',ShiftRight:'boost'},saveKey='forge.skycoil.best.v1';
let best=null;try{best=readBest(localStorage.getItem(saveKey));}catch{}
function showBest(){bestNode.textContent=best?'Local best: '+best.best.toFixed(2)+'s · '+best.cells+' cells. Stored only in this browser.':'No saved local best yet.';}showBest();
function clear(){keyboard.clear();pointers.clear();state.jumpHeld=false;state.buffer=0;}
function message(){status.textContent=state.message;}
function tone(){if(!sound.checked)return;try{audio??=new AudioContext();if(audio.state==='suspended')return;const o=audio.createOscillator(),g=audio.createGain();o.frequency.value=680;g.gain.setValueAtTime(.035,audio.currentTime);g.gain.exponentialRampToValueAtTime(.0001,audio.currentTime+.07);o.connect(g).connect(audio.destination);o.start();o.stop(audio.currentTime+.08);o.onended=()=>{o.disconnect();g.disconnect();};}catch{sound.checked=false;}}
sound.addEventListener('change',async()=>{if(sound.checked){try{audio??=new AudioContext();await audio.resume();tone();}catch{sound.checked=false;}}});
document.getElementById('start').addEventListener('click',()=>{clear();start(state);state.message='Run to the beacon. Jump over red drones.';message();canvas.focus();});
document.getElementById('pause').addEventListener('click',()=>{pause(state);clear();state.message='Paused. Press Resume.';message();});
document.getElementById('restart').addEventListener('click',()=>{clear();state=fresh();start(state);saved=false;message();canvas.focus();});
canvas.addEventListener('keydown',e=>{if(keyMap[e.code]){e.preventDefault();keyboard.add(keyMap[e.code]);}if(e.code==='KeyP'&&!e.repeat){pause(state);clear();state.message='Paused. Press Resume.';message();}});
window.addEventListener('keyup',e=>{if(keyMap[e.code])keyboard.delete(keyMap[e.code]);});
canvas.addEventListener('blur',()=>{keyboard.clear();state.jumpHeld=false;state.buffer=0;});
for(const b of document.querySelectorAll('[data-key]')){b.addEventListener('pointerdown',e=>{e.preventDefault();b.setPointerCapture(e.pointerId);pointers.set(e.pointerId,b.dataset.key);});for(const name of ['pointerup','pointercancel','lostpointercapture'])b.addEventListener(name,e=>pointers.delete(e.pointerId));}
function hidden(){if(document.hidden){clear();pause(state);state.message='Paused while away. Press Resume.';message();}}
document.addEventListener('visibilitychange',hidden);window.addEventListener('blur',()=>{clear();pause(state);message();});window.addEventListener('pagehide',()=>{clear();pause(state);audio?.suspend();});
function frame(now){const dt=last?(now-last)/1000:0;last=now;const input=Object.fromEntries([...keyboard,...pointers.values()].map(k=>[k,true])),cells=state.cells,phase=state.status;advance(state,input,dt);if(state.cells>cells)tone();if(phase!==state.status)message();render(ctx,state,{reduced:motion.matches});hud.textContent='Lives '+state.lives+' · Energy '+Math.round(state.energy)+' · Cells '+state.cells+' · Time '+state.time.toFixed(1)+' / 60s';
 if(state.status==='won'&&!saved){saved=true;if(!best||state.time<best.best){const record={version:1,best:state.time,cells:state.cells};try{localStorage.setItem(saveKey,JSON.stringify(record));best=record;showBest();}catch{bestNode.textContent='Run complete; local storage is unavailable.';}}}requestAnimationFrame(frame);}
message();requestAnimationFrame(frame);

:root{color-scheme:dark;font-family:system-ui,sans-serif;background:#071b25;color:#e0f8f3}body{margin:0}main{max-width:1000px;margin:auto;padding:20px}a{color:#82ffe2}canvas{width:100%;height:auto;display:block;border:1px solid #4b7780;border-radius:16px;outline-offset:4px}button{border:1px solid #77cab6;border-radius:100px;min-width:64px;min-height:52px;background:#163b43;color:#effff8;font:700 14px system-ui;padding:10px 16px;cursor:pointer}button:focus-visible,a:focus-visible{outline:3px solid #ffd578;outline-offset:4px}.menu,.controls{display:flex;gap:10px;flex-wrap:wrap;margin:15px 0}.controls button{touch-action:none;user-select:none}.controls{justify-content:center}.controls button[data-key=jump],.controls button[data-key=boost]{background:#37504a}p{line-height:1.6}#hud{font-variant-numeric:tabular-nums}@media(max-width:500px){main{padding:12px}h1{font-size:26px}.controls{gap:6px}button{padding:8px 12px;min-width:52px}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto}}

# Skycoil Sprint

Original independent MIT browser tutorial. No private BINX Engine code, third-party game source or purchased assets.

Download all eight files (including this README and check.mjs), keeping them together. Serve this folder with any local static HTTP server supporting .mjs as JavaScript; for example, if Python 3 is installed, run `python -m http.server 8080`, then open http://localhost:8080/index.html. Opening index.html as file:// does not load modules consistently. Python is only an optional server; the game has no Python dependency.

Run the actual rules checks with Node 24.19.0 or compatible recent Node: `node check.mjs`.

Controls: A/D or arrows, Space jump, Shift boost. Touch hold buttons are provided. Desktop controls require focus on the canvas. Start/Resume restores focus. One 2400px connected course, jump buffering/coyote time, bounded acceleration, boost energy, pickups, four stationary hazard drones, checkpoint recovery, three lives, 60-second outcome, pause/restart, optional short generated tones and validated browser-local best-time record.

Publish the whole folder on a static HTTPS host with MIME support for .mjs. GitHub Pages instructions: https://docs.github.com/en/pages/getting-started-with-github-pages/creating-a-github-pages-site . Check the exact public URL, keyboard and real phone touch, sound opt-in, tab/focus changes, blocked storage, loss/win and two restarts. Simulation/source-rendered frames do not certify browser input, phone, audio or assistive acceptance.

The game renders its own geometric artwork. The guide's AI concept illustration is a proposed higher-fidelity direction, not this game's screenshot or a downloadable art pack. Stationary hazard drones are obstacles, not pathfinding enemy AI or combat. See the guide's separate ambitious build and upgrade prompts for those systems. No multiplayer, cloud save, 3D exporter or franchise recreation.

MIT License

Copyright (c) 2026 BINX Forge

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

import assert from 'node:assert/strict';
import {fresh,start,pause,advance,damage,readBest,GOAL} from './world.mjs';
let passed=0;function check(name,fn){fn();passed++;console.log('PASS '+name);}
function drive(rate){const s=fresh();start(s);let held=0;for(let i=0;i<rate*60+1&&s.status==='running';i++){const x=s.player.x,near=[440,620,930,1430,1540,1810].some(a=>a-x>0&&a-x<85);if(s.player.grounded&&near&&held<=0)held=.18;advance(s,{right:true,jump:held>0},1/rate);held-=1/rate;}return s;}
check('actual route wins at 15/30/60/120 simulated updates',()=>{for(const rate of [15,30,60,120]){const s=drive(rate);assert.equal(s.status,'won');assert.ok(s.player.x>=GOAL);assert.equal(s.lives,3);assert.ok(s.time<10);}});
check('invalid elapsed time cannot mutate a run; long stalls are capped',()=>{const s=fresh();start(s);const old=JSON.stringify(s);for(const t of [NaN,Infinity,-1,0])advance(s,{right:true},t);assert.equal(JSON.stringify(s),old);advance(s,{right:true},9);assert.ok(s.time<=.100001);assert.ok(s.player.x<90);});
check('boost drains bounded energy and raises movement speed',()=>{const a=fresh(),b=fresh();start(a);start(b);for(let i=0;i<30;i++){advance(a,{right:true},1/120);advance(b,{right:true,boost:true},1/120);}assert.ok(b.player.x>a.player.x);assert.ok(b.energy<a.energy);b.energy=0;advance(b,{right:true,boost:true},.1);assert.ok(b.energy>=0&&b.energy<=100);});
check('jump button hold does not repeatedly jump in midair',()=>{const s=fresh();start(s);advance(s,{jump:true},.05);const before=s.player.vy;advance(s,{jump:true},.05);assert.ok(s.player.vy>before);assert.ok(!s.player.grounded);});
check('pickups award once even after reentering the same cell',()=>{const s=fresh();start(s);s.player.x=200;s.player.y=310;advance(s,{},1/120);assert.equal(s.cells,1);s.player.x=200;s.player.y=310;advance(s,{},1/120);assert.equal(s.cells,1);});
check('damage recovers checkpoint once and preserves collected cells',()=>{const s=fresh();start(s);s.checkpoint=1140;s.cells=2;s.collected=[1,2];damage(s);assert.equal(s.lives,2);assert.equal(s.player.x,1140);assert.equal(s.cells,2);damage(s);assert.equal(s.lives,2);s.immune=0;damage(s);s.immune=0;damage(s);assert.equal(s.status,'lost');});
check('pause, win and loss freeze simulation and restart is independent',()=>{for(const mode of ['paused','won','lost']){const s=fresh();s.status=mode;const old=JSON.stringify(s);advance(s,{right:true,jump:true,boost:true},.1);assert.equal(JSON.stringify(s),old);}const a=drive(60),b=fresh();assert.equal(b.cells,0);assert.equal(b.lives,3);assert.notEqual(a.player,b.player);start(b);pause(b);assert.equal(b.status,'paused');});
check('timeout ends exactly at sixty simulated seconds',()=>{const s=fresh();start(s);s.time=59.99;advance(s,{},.1);assert.equal(s.time,60);assert.equal(s.status,'lost');});
check('local best accepts only versioned bounded values',()=>{assert.deepEqual(readBest('{"version":1,"best":8.8,"cells":9}'),{version:1,best:8.8,cells:9});for(const raw of ['',null,'{}','{"version":2,"best":8,"cells":2}','{"version":1,"best":999,"cells":1}','{"version":1,"best":8,"cells":13}','{"version":1,"best":0,"cells":0}'])assert.equal(readBest(raw),null);});
console.log(passed+' rules checks passed; browser/phone/audio/clipboard acceptance is separate.');

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