Run Detail
completedgpt-6-sol-proRecorded for these videos
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Provider
openrouter
Challenge Version
v1.0
Turns
1
Duration
Batched — not timed
Total Tokens
38,994
Input Tokens
20,297
Output Tokens
18,697
Reasoning Tokens
6,860
Reasoning Effort
default
Est. Cost
$0.1138
Started
9/22/2026, 9:44:58 PM
OR Provider
OpenAI
Finish Reason
stop
Generation ID
gen-batch-1790113498-9babaf2ef1e0fd63ed84
Turns (1)
Turn #1
20,297 in18,697 out6,860 reasoning38,994 total
user
You write simulations where the interesting behavior is supposed to emerge rather than be animated by hand.
Build me a single HTML page: a side-view escalator carrying 15 to 20 people. Then the escalator reverses, at high speed.
The build
- Side view. 15 to 20 figures standing on the steps, riding normally before anything goes wrong.
- A control I can press to throw it into reverse, and press again to put it back. Reversal happens fast enough to take everyone off their feet.
- What follows comes out of the simulation. People stumble, collide, slide, and pile up against each other; a figure that is down is an obstacle to the ones arriving behind it.
- Figures get up again when they have the room and the footing.
- No scripted disaster. No keyframed pile, no timeline, no figure that falls because the clock said so. Every figure runs the same rules. If you special-case anything, say so in the notes.
- The art is yours. Stick figures are fine if they move well.
House rules
- One file. Everything inline — no CDN, no external stylesheet, font, script or image.
data:URIs are fine. - No libraries. No physics engine — write your own.
- No network at runtime.
- No
localStorage,sessionStorage, cookies orindexedDB— sandboxed frame, they throw. - Return the file as exactly one fenced
htmlblock.
Answer in exactly these sections
The model
One paragraph, before the file: how a person is represented, what makes one lose balance, and what happens when two of them occupy the same place.
The page
The single fenced html block.
What it actually does
Having written it, what does the page do when the escalator reverses? Name anything you special-cased or nudged. Say what it does badly — I am going to press the button and watch.
assistant
The model
Each person has a position and velocity along the escalator, a balance offset, and a body angle. Their feet try to match the moving steps; when the steps accelerate faster than their body can follow, that offset grows until they topple. People take up more room while down. When their occupied spaces overlap, the simulation separates them, transfers momentum, and lets the impact disturb their balance. A fallen person can get up only when the belt is no longer dragging them past their footing and there is room nearby.
The page
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Wrong Way — Escalator Simulation</title>
<style>
:root {
color-scheme: dark;
font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
background: #08111c;
color: #edf5f7;
}
* { box-sizing: border-box; }
body {
margin: 0;
min-height: 100vh;
background:
radial-gradient(ellipse at 50% 12%, #173148 0, #0b1928 48%, #08111c 85%);
}
main { width: min(1400px, 100%); margin: auto; padding: 23px clamp(12px, 3vw, 42px) 28px; }
header, .controls {
display: flex;
align-items: center;
justify-content: space-between;
gap: 16px;
flex-wrap: wrap;
}
.eyebrow { color: #78b6c7; font-size: 11px; letter-spacing: .22em; font-weight: 800; }
h1 { margin: 4px 0 3px; font-size: clamp(25px, 3.2vw, 42px); letter-spacing: -.055em; }
header p, .hint { color: #91a9b7; font-size: 13px; margin: 0; }
.tag {
border: 1px solid #426071;
border-radius: 100px;
padding: 7px 12px;
color: #b6d4db;
font: 700 10px ui-monospace, SFMono-Regular, Consolas, monospace;
letter-spacing: .12em;
}
.scene {
position: relative;
margin: 19px 0 16px;
overflow: hidden;
border: 1px solid #345267;
border-radius: 14px;
background: #0c1926;
box-shadow: 0 22px 70px #02070b77, inset 0 0 0 1px #ffffff08;
}
canvas { display: block; width: 100%; aspect-ratio: 16 / 9; }
button {
appearance: none;
border-radius: 8px;
cursor: pointer;
font: 800 13px ui-sans-serif, system-ui, sans-serif;
letter-spacing: .035em;
padding: 13px 18px;
transition: background .15s, transform .15s, border-color .15s;
}
button:active { transform: translateY(2px); }
button:focus-visible { outline: 3px solid #fff; outline-offset: 3px; }
#reverse {
color: #10202a;
border: 1px solid #ffe4a2;
background: #ffc966;
min-width: 212px;
}
#reverse:hover { background: #ffe099; }
#reverse.on { color: #fff; border-color: #ff776e; background: #b83e43; }
#reverse.on:hover { background: #d24e52; }
#reset { color: #d2e3e8; background: #152b3b; border: 1px solid #476073; }
#reset:hover { background: #203c50; }
.controls > div { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.status {
color: #a8d8e2;
font: 700 12px ui-monospace, SFMono-Regular, Consolas, monospace;
letter-spacing: .06em;
}
.hint { line-height: 1.5; }
@media (max-width: 600px) {
main { padding-top: 16px; }
.tag { display: none; }
.hint { width: 100%; }
}
</style>
</head>
<body>
<main>
<header>
<div>
<div class="eyebrow">A LITTLE PHYSICS EXPERIMENT</div>
<h1>Wrong Way</h1>
<p>18 riders. One escalator. No prearranged pile-up.</p>
</div>
<div class="tag">SIDE VIEW / LIVE SIMULATION</div>
</header>
<div class="scene">
<canvas id="view" aria-label="Side-view simulation of people riding an escalator"></canvas>
</div>
<div class="controls">
<div>
<button id="reverse" type="button" aria-pressed="false">↙ Throw into reverse</button>
<button id="reset" type="button">Reset riders</button>
<span class="status" id="status" role="status">BELT: ASCENDING</span>
</div>
<p class="hint">Press reverse again to restore the original direction. Space also toggles it.</p>
</div>
</main>
<script>
(() => {
"use strict";
const canvas = document.getElementById("view");
const ctx = canvas.getContext("2d");
const reverseButton = document.getElementById("reverse");
const resetButton = document.getElementById("reset");
const status = document.getElementById("status");
const W = 1280, H = 720;
const bottom = { x: 153, y: 578 };
const top = { x: 1127, y: 269 };
const length = Math.hypot(top.x - bottom.x, top.y - bottom.y);
const tangent = {
x: (top.x - bottom.x) / length,
y: (top.y - bottom.y) / length
};
const colors = [
"#e99b78", "#9db7e9", "#e1bb6a", "#9ccdb8", "#c5a4db",
"#ec878f", "#a4c2d8", "#dec089", "#89c5cb"
];
const people = [];
let reversed = false;
let belt = 19;
let beltTarget = 19;
let treadOffset = 0;
let lastTime = 0;
let accumulator = 0;
const clamp = (v, lo, hi) => Math.max(lo, Math.min(hi, v));
const point = (s, height = 0) => ({
x: bottom.x + tangent.x * s,
y: bottom.y + tangent.y * s - height
});
function reset() {
people.length = 0;
reversed = false;
belt = beltTarget = 19;
treadOffset = 0;
reverseButton.classList.remove("on");
reverseButton.setAttribute("aria-pressed", "false");
reverseButton.textContent = "↙ Throw into reverse";
status.textContent = "BELT: ASCENDING";
for (let i = 0; i < 18; i++) {
people.push({
id: i,
s: 54 + i * 48,
v: belt,
lean: 0,
leanV: 0,
angle: 0,
angularV: 0,
direction: 1,
state: "up",
downTime: 0,
active: true,
color: colors[i % colors.length],
phase: i * 1.87,
height: 44 + (i * 7 % 9)
});
}
}
function toggle() {
reversed = !reversed;
beltTarget = reversed ? -252 : 19;
reverseButton.classList.toggle("on", reversed);
reverseButton.setAttribute("aria-pressed", String(reversed));
reverseButton.textContent = reversed ? "↗ Restore ascent" : "↙ Throw into reverse";
status.textContent = reversed ? "BELT: FAST DESCENT" : "BELT: ASCENDING";
}
reverseButton.addEventListener("click", toggle);
resetButton.addEventListener("click", reset);
window.addEventListener("keydown", e => {
if (e.code === "Space" && e.target.tagName !== "BUTTON") {
e.preventDefault();
toggle();
}
});
function radius(p) {
return p.state === "up" ? 15 : 27;
}
function topple(p) {
if (p.state !== "up") return;
p.state = "down";
p.downTime = 0;
p.direction = (p.lean || p.leanV || 1) >= 0 ? 1 : -1;
p.angle = clamp(Math.atan(p.lean / 37), -0.48, 0.48);
p.angularV = clamp(p.leanV / 37, -6, 6);
}
function step(dt) {
// The motor changes speed quickly. The riders are not assigned its velocity.
belt += (beltTarget - belt) * (1 - Math.exp(-dt / 0.075));
treadOffset += belt * dt;
for (const p of people) {
if (!p.active) continue;
const standing = p.state === "up";
const desiredAcceleration = (belt - p.v) * (standing ? 13 : 4);
const acceleration = clamp(
desiredAcceleration,
standing ? -1100 : -350,
standing ? 1100 : 350
);
p.v += acceleration * dt;
p.s += p.v * dt;
if (standing) {
// Inertia throws the upper body past the accelerating feet.
p.leanV += (-70 * p.lean - 11 * p.leanV - 1.9 * acceleration) * dt;
p.lean += p.leanV * dt;
p.angle = clamp(Math.atan(p.lean / 37), -0.48, 0.48);
if (Math.abs(p.lean) > 13.5) topple(p);
} else {
p.downTime += dt;
p.leanV *= Math.exp(-7 * dt);
p.lean *= Math.exp(-5 * dt);
const targetAngle = p.state === "down" ? p.direction * 1.36 : 0;
p.angularV += ((targetAngle - p.angle) * 48 - p.angularV * 12) * dt;
p.angle += p.angularV * dt;
if (p.state === "rising" &&
Math.abs(p.angle) < 0.09 &&
Math.abs(p.angularV) < 0.45) {
p.state = "up";
p.angle = p.lean = p.leanV = 0;
}
}
}
// All riders use the same one-dimensional contact rules. A person lying
// across the steps has a larger collision footprint.
for (let pass = 0; pass < 4; pass++) {
const ordered = people.filter(p => p.active).sort((a, b) => a.s - b.s);
for (let i = 0; i < ordered.length - 1; i++) {
const a = ordered[i], b = ordered[i + 1];
const overlap = radius(a) + radius(b) - (b.s - a.s);
if (overlap <= 0) continue;
const invA = a.state === "up" ? 1 : 0.65;
const invB = b.state === "up" ? 1 : 0.65;
const correction = overlap / (invA + invB);
a.s -= correction * invA;
b.s += correction * invB;
const closingSpeed = a.v - b.v;
if (closingSpeed > 0) {
const impulse = closingSpeed * 0.73 / (invA + invB);
const oldA = a.v, oldB = b.v;
a.v -= impulse * invA;
b.v += impulse * invB;
if (a.state === "up") a.leanV -= (a.v - oldA) * 2.1;
if (b.state === "up") b.leanV -= (b.v - oldB) * 2.1;
}
}
}
for (const p of people) {
if (!p.active) continue;
// Solid landing ends: riders cannot move through the machinery.
const low = 13, high = length - 9;
if (p.s < low) {
p.s = low;
if (p.v < 0) {
if (p.state === "up") p.leanV -= (-p.v) * 1.6;
p.v = 0;
}
}
if (p.s > high) {
p.s = high;
if (p.v > 0) {
if (p.state === "up") p.leanV += p.v * 1.6;
p.v = 0;
}
}
if (p.state === "up" && Math.abs(p.lean) > 13.5) topple(p);
if (p.state === "down" && p.downTime > 0.85 &&
Math.abs(p.v - belt) < 52 && Math.abs(p.v) < 75) {
const hasRoom = people.every(other =>
other === p || !other.active ||
Math.abs(other.s - p.s) > 19 + radius(other)
);
if (hasRoom) p.state = "rising";
}
// A renewed shove or loss of footing interrupts an attempt to stand.
if (p.state === "rising" && Math.abs(p.v - belt) > 100) {
p.state = "down";
p.direction = p.angle >= 0 ? 1 : -1;
}
}
// The top landing is an exit during ordinary ascent. Re-enter at the
// bottom only when the entrance is clear; nobody is recycled in reverse.
if (!reversed && belt > 0) {
for (const p of people) {
if (p.active && p.state === "up" && p.s > length - 25) {
p.active = false;
}
}
for (const p of people) {
if (p.active) continue;
const entranceClear = people.every(q =>
!q.active || q.s > 58
);
if (entranceClear) {
p.active = true;
p.s = 14;
p.v = belt;
p.lean = p.leanV = p.angle = p.angularV = 0;
p.state = "up";
}
}
}
}
function line(x1, y1, x2, y2, color, width = 1) {
ctx.strokeStyle = color;
ctx.lineWidth = width;
ctx.beginPath();
ctx.moveTo(x1, y1);
ctx.lineTo(x2, y2);
ctx.stroke();
}
function roundedBar(x1, y1, x2, y2, color, width) {
ctx.strokeStyle = color;
ctx.lineWidth = width;
ctx.lineCap = "round";
ctx.beginPath();
ctx.moveTo(x1, y1);
ctx.lineTo(x2, y2);
ctx.stroke();
}
function drawArchitecture() {
ctx.fillStyle = "#0c1c2a";
ctx.fillRect(0, 0, W, H);
// Sparse wall markings give the motion a fixed reference.
for (let x = 45; x < W; x += 96) {
line(x, 48, x, 646, "#28405249");
}
for (let y = 82; y < 650; y += 92) {
line(34, y, 1246, y, "#2840523b");
}
ctx.fillStyle = "#12283a";
ctx.fillRect(0, 596, 175, 124);
ctx.fillRect(1100, 294, 180, 426);
ctx.fillStyle = "#1b3445";
ctx.fillRect(0, 594, 178, 10);
ctx.fillRect(1096, 290, 184, 10);
line(0, 605, 174, 605, "#71a8b0", 2);
line(1099, 301, 1280, 301, "#71a8b0", 2);
// Escalator carcass, with the steps moving separately over it.
const a = point(-18), b = point(length + 15);
ctx.fillStyle = "#203747";
ctx.beginPath();
ctx.moveTo(a.x, a.y - 5);
ctx.lineTo(b.x, b.y - 5);
ctx.lineTo(b.x, b.y + 53);
ctx.lineTo(a.x, a.y + 53);
ctx.closePath();
ctx.fill();
line(a.x, a.y + 51, b.x, b.y + 51, "#09202d", 8);
line(a.x, a.y + 43, b.x, b.y + 43, "#4c6b78", 3);
ctx.save();
ctx.beginPath();
ctx.moveTo(a.x, a.y - 3);
ctx.lineTo(b.x, b.y - 3);
ctx.lineTo(b.x, b.y + 18);
ctx.lineTo(a.x, a.y + 18);
ctx.closePath();
ctx.clip();
ctx.fillStyle = "#294656";
ctx.fillRect(0, 0, W, H);
const spacing = 43;
const phase = ((treadOffset % spacing) + spacing) % spacing;
for (let s = -spacing * 2 + phase; s < length + spacing * 2; s += spacing) {
const p = point(s);
const n = { x: -tangent.y, y: tangent.x };
line(p.x - n.x * 5, p.y - n.y * 5,
p.x + n.x * 23, p.y + n.y * 23, "#081d2b", 5);
line(p.x + 7, p.y + 5, p.x + 27, p.y + 5,
"#7296a0", 2);
}
ctx.restore();
line(a.x, a.y - 4, b.x, b.y - 4, "#92b4b7", 4);
line(a.x, a.y + 17, b.x, b.y + 17, "#0d2735", 4);
// Rear handrail: behind the riders.
const railA = point(-29, 65), railB = point(length + 27, 65);
line(railA.x, railA.y + 9, railB.x, railB.y + 9, "#0a1b2a", 13);
line(railA.x, railA.y, railB.x, railB.y, "#577985", 7);
line(railA.x, railA.y - 3, railB.x, railB.y - 3, "#9bb9b7", 2);
for (let s = 17; s < length; s += 167) {
const r = point(s, 64), foot = point(s, -16);
line(r.x, r.y + 4, foot.x, foot.y, "#52717c", 4);
ctx.fillStyle = "#83a2a9";
ctx.beginPath();
ctx.arc(r.x, r.y + 3, 4, 0, Math.PI * 2);
ctx.fill();
}
// Signs and landing details.
ctx.font = "700 12px ui-monospace, monospace";
ctx.letterSpacing = "2px";
ctx.fillStyle = "#7395a4";
ctx.fillText("LOWER LANDING", 32, 653);
ctx.fillText("UPPER LANDING", 1092, 357);
ctx.letterSpacing = "0px";
ctx.fillStyle = "#ffcf75";
ctx.fillRect(86, 585, 71, 5);
ctx.fillRect(1114, 280, 87, 5);
ctx.fillStyle = "#3b5968";
ctx.fillRect(37, 437, 42, 86);
ctx.fillStyle = reversed ? "#ff7971" : "#85d6c5";
ctx.fillRect(49, 449, 18, 18);
ctx.fillStyle = "#a8c3c9";
ctx.font = "700 11px ui-monospace, monospace";
ctx.fillText("MOTOR", 35, 541);
ctx.fillStyle = "#60808d";
ctx.font = "12px ui-monospace, monospace";
ctx.fillText("18 INDEPENDENT RIDERS", 37, 69);
ctx.fillText(reversed ? "DIRECTION ↙ FAST" : "DIRECTION ↗ NORMAL", 37, 91);
}
function drawPerson(p) {
const f = point(p.s);
const angle = p.angle;
const sine = Math.sin(angle), cosine = Math.cos(angle);
const h = p.height;
const up = (distance) => ({
x: f.x + tangent.x * sine * distance,
y: f.y + tangent.y * sine * distance - cosine * distance
});
const hip = up(h * 0.35);
const shoulder = up(h * 0.83);
const head = up(h + 5);
const walking = p.state === "up"
? Math.sin(p.s * 0.12 + p.phase) * Math.min(2.5, Math.abs(p.v) * 0.022)
: Math.sin(p.angle * 4 + p.phase) * 3;
ctx.save();
ctx.lineJoin = "round";
ctx.lineCap = "round";
// Contact shadow.
ctx.fillStyle = "#07131cad";
ctx.beginPath();
ctx.ellipse(f.x, f.y + 4, p.state === "up" ? 13 : 26, 4, -0.3, 0, Math.PI * 2);
ctx.fill();
const ink = "#102333";
const skin = ["#f5c9aa", "#dfaa88", "#b98468", "#f1bfa1"][p.id % 4];
const sideways = p.state === "up" ? 6 : 12;
// Legs respond to body orientation rather than following a fall animation.
roundedBar(hip.x - 3, hip.y, f.x - sideways + walking, f.y - 2, ink, 9);
roundedBar(hip.x + 3, hip.y, f.x + sideways - walking, f.y - 2, ink, 9);
roundedBar(f.x - sideways + walking, f.y - 2,
f.x - sideways + walking + 6, f.y - 1, "#6c8590", 5);
roundedBar(f.x + sideways - walking, f.y - 2,
f.x + sideways - walking + 6, f.y - 1, "#6c8590", 5);
roundedBar(hip.x, hip.y, shoulder.x, shoulder.y, ink, 15);
roundedBar(hip.x, hip.y, shoulder.x, shoulder.y, p.color, 11);
ctx.fillStyle = "#ffffff32";
ctx.beginPath();
ctx.arc(shoulder.x - 2, shoulder.y, 2.1, 0, Math.PI * 2);
ctx.fill();
const armReach = p.state === "up" ? 8 : 16;
roundedBar(shoulder.x - 4, shoulder.y + 2,
shoulder.x - armReach - sine * 5,
shoulder.y + 16 * cosine + 8, ink, 6);
roundedBar(shoulder.x + 4, shoulder.y + 2,
shoulder.x + armReach + sine * 5,
shoulder.y + 13 * cosine + (p.state === "up" ? walking : -8),
skin, 5);
ctx.fillStyle = skin;
ctx.strokeStyle = ink;
ctx.lineWidth = 2.8;
ctx.beginPath();
ctx.arc(head.x, head.y, 6.6, 0, Math.PI * 2);
ctx.fill();
ctx.stroke();
// Small hair arc to keep the head's orientation readable.
ctx.strokeStyle = ink;
ctx.lineWidth = 3;
ctx.beginPath();
ctx.arc(head.x - 1, head.y - 1, 6, Math.PI * 1.05, Math.PI * 1.83);
ctx.stroke();
ctx.restore();
}
function draw() {
drawArchitecture();
people.filter(p => p.active).sort((a, b) => b.s - a.s).forEach(drawPerson);
// Foreground edge of the moving assembly.
const a = point(-17, -21), b = point(length + 13, -21);
line(a.x, a.y, b.x, b.y, "#081b28", 10);
line(a.x, a.y - 4, b.x, b.y - 4, "#678b94", 3);
ctx.fillStyle = "#97b5bd";
ctx.font = "11px ui-monospace, monospace";
ctx.fillText("CONTACTS • MOMENTUM • BALANCE • RECOVERY", 37, 689);
}
function resize() {
const dpr = Math.min(window.devicePixelRatio || 1, 2);
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canvas.width = Math.round(rect.width * dpr);
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ctx.setTransform(canvas.width / W, 0, 0, canvas.height / H, 0, 0);
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accumulator += Math.min((time - lastTime) / 1000, 0.08);
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const dt = 1 / 120;
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step(dt);
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What it actually does
Reversing sharply changes the step speed. Riders initially retain their momentum, lean past their balance limit, and fall; subsequent contact and the faster-descending belt move them toward the lower landing, where fallen riders obstruct those behind. Restoring ascent lets riders with space and sufficiently steady footing stand again.
The nudges are the chosen balance threshold, stronger contact footprint for a fallen rider, solid landing boundaries, and recycling upright riders from the upper exit to an empty lower entrance during normal ascent. Nobody is selected to fall at a particular time. It is deliberately a one-dimensional contact model: the figures cannot step around one another, and its drawn limbs are expressive rather than independently simulated.
Attachments
openai/gpt-6-sol-pro — page