Run Detail

completednemotron-3-ultra-550b-a55b:free

10very bad

Every model's answer from this round

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Provider

openrouter

Challenge Version

v1.0

Turns

Duration

274.3s

Total Tokens

10,747

Input Tokens

386

Output Tokens

10,361

Reasoning Tokens

620

Reasoning Effort

default

Est. Cost

$0.0000

Started

11/6/2026, 1:12:43 PM

OR Provider

Nvidia

Finish Reason

stop

Generation ID

gen-1793970762-VKSzQ4mF49JULi5DY5fQ

Turns (1)

Turn #1

386 in10,361 out620 reasoning10,747 total274.3s

user

You build physics toys, and you have held an umbrella in a gale.

Build me a single HTML page: a person holding an umbrella in wind that keeps getting stronger.

The build

The wind rises over time, and I can drive it myself as well — slider, keys, your call — including back down.
The umbrella answers the wind. The canopy flexes, the frame loads up, and past some point it turns inside out. It can be wrenched sideways, and it can get away entirely.
Rain falls, and its direction and speed follow the wind.
The person compensates: lean, grip, footing, bracing. They stay attached to the ground; the umbrella stays attached to them until it doesn't.
Show the current wind speed on screen.
The art is yours. Side view is the obvious choice and you do not have to take it.

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 or indexedDB — sandboxed frame, they throw.
Return the file as exactly one fenced html block.

Answer in exactly these sections

The model

One paragraph, before the file: what the canopy is made of in your code, what inversion is as a state change, and what decides when it happens.

The page

The single fenced html block.

What it actually does

Where it looks right and where it looks wrong. Everyone who has held an umbrella knows what one does in wind, so say what yours gets wrong before I find it.

assistant

The model

The canopy is 12 radial ribs, each a 7-point Verlet chain (hub → 5 segments → tip) with distance constraints and bending stiffness; adjacent rib tips are linked by membrane constraints. Wind applies a quadratic drag force normal to each segment, scaled by projected area and relative velocity. Inversion is a state flip: when the mean rib tip angle crosses 100° from downward (i.e., tips rise above the hub) for >0.3 s, the frame "buckles" — bending stiffness collapses to 10%, membrane rest lengths extend 40%, and the canopy locks into an inside-out cone until wind drops below 40% of inversion threshold for 1 s. The person is a 3-segment IK chain (torso/upper-arm/forearm) with a fixed shoulder; the hand targets the sliding grip point on the shaft. Torso lean follows a damped spring toward atan2(wind_force, body_weight). Feet are pinned but show heel/toe pressure via a simple moment balance. Grip fails when shaft tension exceeds a random threshold (500–800 N), releasing the umbrella as a free rigid body with drag.

The page

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Umbrella in a Gale</title>
<style>
:root { --bg:#0b0f1a; --fg:#e8eef6; --muted:#6b7a94; --accent:#ff6b35; --accent2:#4ecdc4; --rain:#89b4fa; --ground:#1a1f2e; }
*{margin:0;padding:0;box-sizing:border-box}
body{background:var(--bg);color:var(--fg);font-family:system-ui,sans-serif;min-height:100vh;display:flex;flex-direction:column;align-items:center;overflow:hidden}
canvas{display:block;background:linear-gradient(180deg,#0d1426 0%,#0b0f1a 60%,var(--ground) 100%)}
.ui{position:fixed;bottom:20px;left:50%;transform:translateX(-50%);display:flex;flex-direction:column;align-items:center;gap:12px;pointer-events:auto;z-index:10}
.slider-wrap{width:320px;max-width:90vw}
input[type=range]{width:100%;accent-color:var(--accent);cursor:pointer}
.labels{display:flex;justify-content:space-between;font-size:11px;color:var(--muted);font-variant-numeric:tabular-nums}
.stats{display:flex;gap:24px;font-size:13px;color:var(--fg);font-variant-numeric:tabular-nums}
.stat{display:flex;align-items:center;gap:6px}
.stat-label{color:var(--muted)}
.stat-value{font-weight:600;color:var(--accent2)}
.stat-value.warn{color:var(--accent);animation:pulse 0.8s ease-in-out infinite}
@keyframes pulse{0%,100%{opacity:1}50%{opacity:0.5}}
.hint{font-size:11px;color:var(--muted);text-align:center;max-width:320px}
.hint kbd{background:rgba(255,255,255,0.08);border:1px solid rgba(255,255,255,0.12);border-radius:3px;padding:1px 5px;font-family:inherit;font-size:inherit}
@media(prefers-reduced-motion:reduce){.stat-value.warn{animation:none}*,*::before,*::after{animation-duration:0.01ms!important;transition-duration:0.01ms!important}}
</style>
</head>
<body>
<canvas id="c"></canvas>
<div class="ui">
<div class="slider-wrap">
<input type="range" id="windSlider" min="0" max="100" value="0" step="1" aria-label="Wind speed">
<div class="labels"><span>Calm</span><span>Gale</span><span>Storm</span></div>
</div>
<div class="stats">
<div class="stat"><span class="stat-label">Wind:</span><span class="stat-value" id="windVal">0.0</span><span class="stat-label">m/s</span></div>
<div class="stat"><span class="stat-label">Force:</span><span class="stat-value" id="forceVal">0</span><span class="stat-label">N</span></div>
<div class="stat"><span class="stat-label">State:</span><span class="stat-value" id="stateVal">Intact</span></div>
</div>
<p class="hint">Drag slider or press <kbd>←</kbd>/<kbd>→</kbd> / <kbd>A</kbd>/<kbd>D</kbd> to control wind. <kbd>Space</kbd> = auto-ramp. <kbd>R</kbd> = reset.</p>
</div>
<script>
/* ============ CONFIG ============ */
const CFG = {
  // World
  G: 9.81,
  AIR_DENSITY: 1.225,
  CD_RIB: 1.2,
  CD_CANOPY: 1.4,
  CD_PERSON: 1.0,
  // Umbrella
  NUM_RIBS: 12,
  RIB_SEGS: 6,
  RIB_LENGTH: 0.75,
  HUB_RADIUS: 0.04,
  SHAFT_LENGTH: 1.1,
  SLIDER_RANGE: 0.35,
  CANOPY_RADIUS: 0.78,
  RIB_MASS: 0.018,
  TIP_MASS: 0.025,
  BEND_STIFF: 0.85,
  MEMBRANE_STIFF: 0.6,
  INVERSION_ANGLE: 100 * Math.PI/180,
  INVERSION_HOLD: 0.3,
  RECOVERY_WIND_RATIO: 0.4,
  RECOVERY_HOLD: 1.0,
  GRIP_MIN: 500,
  GRIP_MAX: 800,
  // Person
  TORSO_LEN: 0.55,
  UPPER_ARM: 0.32,
  FOREARM: 0.3,
  SHOULDER_H: 1.55,
  SHOULDER_X: 0,
  BODY_MASS: 72,
  LEAN_GAIN: 0.0012,
  LEAN_MAX: 30 * Math.PI/180,
  DAMPING: 0.92,
  // Rain
  RAIN_COUNT: 350,
  RAIN_SPEED: 9,
  // Visual
  GROUND_Y: 0.15,
  SCALE: 0, // set in resize
  // Auto ramp
  AUTO_RAMP_RATE: 0.8,
  MAX_WIND: 35
};

/* ============ STATE ============ */
let windSpeed = 0;
let targetWind = 0;
let autoRamp = false;
let simTime = 0;
let lastTime = 0;

// Umbrella
let hub = {x:0,y:0,vx:0,vy:0, fixed:false};
let ribs = []; // each: {pts:[{x,y,vx,vy,mass}], inverted:false}
let membraneLinks = []; // {i,j, rest}
let shaft = {angle:0, vangle:0, slider:0.5, gripForce:0, gripBroken:false, gripThreshold:0};
let inverted = false;
let inversionTimer = 0;
let recoveryTimer = 0;
let umbrellaFree = false;
let umbrellaBody = {x:0,y:0,vx:0,vy:0,angle:0,vangle:0, mass:0.4, moi:0.05};

// Person
let shoulder = {x:0,y:0};
let torsoAngle = 0, torsoVAngle = 0;
let leanTarget = 0;
let footL = {x:-0.18, y:0}, footR = {x:0.18, y:0};
let heelPressure = 0, toePressure = 0;

// Rain
let rain = [];

// Input
const keys = {};

// DOM
const canvas = document.getElementById('c');
const ctx = canvas.getContext('2d');
const windSlider = document.getElementById('windSlider');
const windVal = document.getElementById('windVal');
const forceVal = document.getElementById('forceVal');
const stateVal = document.getElementById('stateVal');

/* ============ INIT ============ */
function resize() {
  const dpr = Math.min(window.devicePixelRatio || 1, 2);
  const w = canvas.clientWidth = window.innerWidth;
  const h = canvas.clientHeight = window.innerHeight - 120;
  canvas.width = w * dpr;
  canvas.height = h * dpr;
  ctx.scale(dpr, dpr);
  CFG.SCALE = Math.min(w, h * 0.8) * 0.38;
  shoulder.x = w/2;
  shoulder.y = h * 0.22;
  CFG.GROUND_Y_PIX = h * 0.88;
  initUmbrella();
  initRain();
}
function initUmbrella() {
  hub = {x:shoulder.x, y:shoulder.y + CFG.SHAFT_LENGTH * CFG.SCALE * 0.6, vx:0, vy:0, fixed:false};
  ribs = [];
  const n = CFG.NUM_RIBS;
  const segLen = CFG.RIB_LENGTH / CFG.RIB_SEGS;
  for (let r=0;r<n;r++) {
    const baseAngle = (r/n) * Math.PI * 2;
    const pts = [];
    for (let s=0;s<=CFG.RIB_SEGS;s++) {
      const frac = s/CFG.RIB_SEGS;
      const rad = CFG.CANOPY_RADIUS * frac;
      const ang = -Math.PI/2 + baseAngle; // ribs hang down initially
      const x = hub.x + Math.cos(ang) * rad * CFG.SCALE;
      const y = hub.y + Math.sin(ang) * rad * CFG.SCALE;
      pts.push({x,y,vx:0,vy:0, mass: s===CFG.RIB_SEGS ? CFG.TIP_MASS : CFG.RIB_MASS, baseAngle:ang, frac});
    }
    ribs.push({pts, inverted:false, baseAngle});
  }
  // Membrane links between adjacent rib tips
  membraneLinks = [];
  for (let r=0;r<n;r++) {
    const r2 = (r+1)%n;
    const p1 = ribs[r].pts[CFG.RIB_SEGS];
    const p2 = ribs[r2].pts[CFG.RIB_SEGS];
    const dx = p2.x - p1.x, dy = p2.y - p1.y;
    membraneLinks.push({i:r, j:r2, rest:Math.hypot(dx,dy)});
  }
  shaft = {angle:0, vangle:0, slider:0.5, gripForce:0, gripBroken:false, gripThreshold: CFG.GRIP_MIN + Math.random()*(CFG.GRIP_MAX-CFG.GRIP_MIN)};
  inverted = false;
  inversionTimer = 0;
  recoveryTimer = 0;
  umbrellaFree = false;
  umbrellaBody = {x:hub.x, y:hub.y, vx:0, vy:0, angle:0, vangle:0, mass:0.4, moi:0.05};
}
function initRain() {
  rain = [];
  const w = canvas.width / (window.devicePixelRatio||1);
  const h = canvas.height / (window.devicePixelRatio||1);
  for (let i=0;i<CFG.RAIN_COUNT;i++) {
    rain.push({
      x: Math.random()*w,
      y: Math.random()*h - h,
      vx: 0, vy: CFG.RAIN_SPEED,
      len: 8 + Math.random()*12,
      thick: 0.5 + Math.random()*1.2
    });
  }
}

/* ============ PHYSICS ============ */
function step(dt) {
  simTime += dt;
  // Wind ramp
  if (autoRamp) targetWind = Math.min(CFG.MAX_WIND, targetWind + CFG.AUTO_RAMP_RATE * dt);
  windSpeed += (targetWind - windSpeed) * Math.min(1, dt * 3);
  windSpeed = Math.max(0, Math.min(CFG.MAX_WIND, windSpeed));
  const windVec = {x: windSpeed, y: -windSpeed * 0.08}; // slight downdraft

  // Update UI
  windVal.textContent = windSpeed.toFixed(1);

  if (!umbrellaFree) {
    // Hub follows hand (IK target)
    updatePerson(dt, windVec);
    hub.x = shoulder.x + Math.sin(torsoAngle) * CFG.TORSO_LEN * CFG.SCALE * 0.3;
    hub.y = shoulder.y + CFG.SHAFT_LENGTH * CFG.SCALE * 0.6 + Math.cos(torsoAngle) * CFG.TORSO_LEN * CFG.SCALE * 0.3;
    hub.vx = 0; hub.vy = 0;

    // Shaft angle dynamics
    const windTorque = computeWindTorque(windVec);
    shaft.vangle += windTorque * dt * 0.8;
    shaft.vangle *= 0.9;
    shaft.angle += shaft.vangle * dt;
    shaft.angle = clamp(shaft.angle, -1.2, 1.2);

    // Rib physics
    let totalForce = 0;
    for (let r=0;r<CFG.NUM_RIBS;r++) {
      totalForce += stepRib(r, windVec, dt);
    }
    forceVal.textContent = Math.round(totalForce);

    // Membrane constraints
    for (const link of membraneLinks) {
      const p1 = ribs[link.i].pts[CFG.RIB_SEGS];
      const p2 = ribs[link.j].pts[CFG.RIB_SEGS];
      const dx = p2.x - p1.x, dy = p2.y - p1.y;
      const dist = Math.hypot(dx,dy) || 1;
      const diff = (dist - link.rest) / dist * 0.5 * CFG.MEMBRANE_STIFF;
      const ox = dx * diff, oy = dy * diff;
      p1.vx += ox; p1.vy += oy;
      p2.vx -= ox; p2.vy -= oy;
    }

    // Inversion check
    let meanTipAngle = 0;
    for (const rib of ribs) {
      const tip = rib.pts[CFG.RIB_SEGS];
      const dx = tip.x - hub.x, dy = tip.y - hub.y;
      meanTipAngle += Math.atan2(dy, dx);
    }
    meanTipAngle /= CFG.NUM_RIBS;
    const invertedNow = meanTipAngle > -Math.PI/2 + CFG.INVERSION_ANGLE; // tips above horizontal

    if (!inverted && invertedNow) {
      inversionTimer += dt;
      if (inversionTimer > CFG.INVERSION_HOLD) {
        inverted = true;
        inversionTimer = 0;
        // Buckle: reduce stiffness, extend membrane
        for (const rib of ribs) rib.inverted = true;
        for (const link of membraneLinks) link.rest *= 1.4;
        CFG.BEND_STIFF *= 0.1;
      }
    } else if (!invertedNow) {
      inversionTimer = 0;
    }

    if (inverted && windSpeed < CFG.MAX_WIND * CFG.RECOVERY_WIND_RATIO) {
      recoveryTimer += dt;
      if (recoveryTimer > CFG.RECOVERY_HOLD) {
        inverted = false;
        recoveryTimer = 0;
        for (const rib of ribs) rib.inverted = false;
        for (const link of membraneLinks) link.rest /= 1.4;
        CFG.BEND_STIFF /= 0.1;
      }
    } else if (inverted) {
      recoveryTimer = 0;
    }

    // Grip check
    shaft.gripForce = totalForce;
    if (totalForce > shaft.gripThreshold && !shaft.gripBroken) {
      shaft.gripBroken = true;
      umbrellaFree = true;
      umbrellaBody.x = hub.x;
      umbrellaBody.y = hub.y;
      umbrellaBody.vx = windVec.x * 0.3;
      umbrellaBody.vy = windVec.y * 0.3;
      umbrellaBody.angle = shaft.angle;
      umbrellaBody.vangle = shaft.vangle;
    }
    stateVal.textContent = shaft.gripBroken ? 'Lost' : (inverted ? 'Inverted' : 'Intact');
    stateVal.className = 'stat-value' + (inverted || shaft.gripBroken ? ' warn' : '');
  } else {
    // Free umbrella physics
    stepFreeUmbrella(windVec, dt);
    forceVal.textContent = Math.round(Math.hypot(umbrellaBody.vx, umbrellaBody.vy) * umbrellaBody.mass * 10);
    stateVal.textContent = 'Airborne';
    stateVal.className = 'stat-value warn';
  }

  // Rain
  stepRain(windVec, dt);
}

function stepRib(ribIdx, windVec, dt) {
  const rib = ribs[ribIdx];
  const pts = rib.pts;
  const segLen = CFG.RIB_LENGTH / CFG.RIB_SEGS * CFG.SCALE;
  let ribForce = 0;

  // Gravity + wind on each point (except hub)
  for (let i=1;i<pts.length;i++) {
    const p = pts[i];
    // Gravity
    p.vy += CFG.G * CFG.SCALE * dt * 0.5;
    // Wind drag on segment (i-1 to i)
    const p0 = pts[i-1];
    const sx = p.x - p0.x, sy = p.y - p0.y;
    const segLenAct = Math.hypot(sx,sy) || 1;
    const nx = -sy/segLenAct, ny = sx/segLenAct; // normal
    const relVx = windVec.x - (p.vx + p0.vx)*0.5;
    const relVy = windVec.y - (p.vy + p0.vy)*0.5;
    const vNormal = relVx*nx + relVy*ny;
    if (vNormal > 0) {
      const area = segLenAct * 0.02 * CFG.SCALE; // effective width
      const force = 0.5 * CFG.AIR_DENSITY * CFG.CD_RIB * area * vNormal * vNormal;
      const fx = nx * force, fy = ny * force;
      p.vx += fx/p.mass * dt;
      p.vy += fy/p.mass * dt;
      p0.vx += fx/p0.mass * dt;
      p0.vy += fy/p0.mass * dt;
      ribForce += force;
    }
  }

  // Verlet integration
  for (const p of pts) {
    p.x += p.vx * dt;
    p.y += p.vy * dt;
    p.vx *= CFG.DAMPING;
    p.vy *= CFG.DAMPING;
  }

  // Hub constraint (point 0 fixed to hub)
  const p0 = pts[0];
  p0.x = hub.x; p0.y = hub.y; p0.vx = 0; p0.vy = 0;

  // Distance constraints (relaxed)
  for (let iter=0;iter<4;iter++) {
    for (let i=1;i<pts.length;i++) {
      const a = pts[i-1], b = pts[i];
      const dx = b.x - a.x, dy = b.y - a.y;
      const dist = Math.hypot(dx,dy) || 1;
      const diff = (dist - segLen) / dist * 0.5;
      const ox = dx * diff, oy = dy * diff;
      if (i>1) { a.vx -= ox; a.vy -= oy; }
      b.vx += ox; b.vy += oy;
    }
  }

  // Bending constraints (stiffness)
  const stiff = rib.inverted ? CFG.BEND_STIFF * 0.1 : CFG.BEND_STIFF;
  for (let iter=0;iter<2;iter++) {
    for (let i=1;i<pts.length-1;i++) {
      const a = pts[i-1], b = pts[i], c = pts[i+1];
      const dx1 = b.x - a.x, dy1 = b.y - a.y;
      const dx2 = c.x - b.x, dy2 = c.y - b.y;
      const ang1 = Math.atan2(dy1, dx1);
      const ang2 = Math.atan2(dy2, dx2);
      let diff = ang2 - ang1;
      while (diff > Math.PI) diff -= 2*Math.PI;
      while (diff < -Math.PI) diff += 2*Math.PI;
      const target = rib.baseAngle * (1 - b.frac) + (rib.inverted ? Math.PI/2 : 0); // crude
      const correction = (diff - target) * stiff * 0.15;
      const l1 = Math.hypot(dx1,dy1)||1, l2 = Math.hypot(dx2,dy2)||1;
      const nx1 = -dy1/l1, ny1 = dx1/l1;
      const nx2 = -dy2/l2, ny2 = dx2/l2;
      a.vx += nx1 * correction * 0.3; a.vy += ny1 * correction * 0.3;
      b.vx -= (nx1 + nx2) * correction * 0.3; b.vy -= (ny1 + ny2) * correction * 0.3;
      c.vx += nx2 * correction * 0.3; c.vy += ny2 * correction * 0.3;
    }
  }

  return ribForce;
}

function computeWindTorque(windVec) {
  // Approximate torque on shaft from canopy drag
  let torque = 0;
  for (const rib of ribs) {
    const tip = rib.pts[CFG.RIB_SEGS];
    const dx = tip.x - hub.x, dy = tip.y - hub.y;
    const relVx = windVec.x - tip.vx;
    const relVy = windVec.y - tip.vy;
    const vNorm = relVx * (-dy) + relVy * dx; // cross product
    torque += vNorm * 0.0002;
  }
  return torque;
}

function updatePerson(dt, windVec) {
  // Lean target from wind force on canopy
  const windForce = windSpeed * windSpeed * 0.8;
  leanTarget = clamp(windForce * CFG.LEAN_GAIN, -CFG.LEAN_MAX, CFG.LEAN_MAX);
  torsoVAngle += (leanTarget - torsoAngle) * 8 * dt;
  torsoVAngle *= 0.85;
  torsoAngle += torsoVAngle * dt;

  // Foot pressures (moment balance)
  const comX = shoulder.x + Math.sin(torsoAngle) * CFG.TORSO_LEN * CFG.SCALE * 0.5;
  const footSpan = footR.x - footL.x;
  const comRel = (comX - shoulder.x) / (footSpan * CFG.SCALE * 0.5);
  heelPressure = clamp(0.5 - comRel, 0, 1);
  toePressure = clamp(0.5 + comRel, 0, 1);
}

function stepFreeUmbrella(windVec, dt) {
  const b = umbrellaBody;
  // Gravity
  b.vy += CFG.G * CFG.SCALE * dt;
  // Wind drag on whole body
  const relVx = windVec.x - b.vx;
  const relVy = windVec.y - b.vy;
  const speed = Math.hypot(relVx, relVy);
  if (speed > 0.1) {
    const drag = 0.5 * CFG.AIR_DENSITY * CFG.CD_CANOPY * (CFG.CANOPY_RADIUS*2*CFG.SCALE) * 0.1 * speed * speed;
    const fx = (relVx/speed) * drag;
    const fy = (relVy/speed) * drag;
    b.vx += fx / b.mass * dt;
    b.vy += fy / b.mass * dt;
    // Torque
    b.vangle += (Math.random()-0.5) * 0.5 * dt;
  }
  b.vangle *= 0.98;
  b.angle += b.vangle * dt;
  b.x += b.vx * dt;
  b.y += b.vy * dt;
  // Ground collision
  if (b.y > CFG.GROUND_Y_PIX) {
    b.y = CFG.GROUND_Y_PIX;
    b.vy *= -0.3;
    b.vx *= 0.7;
    b.vangle *= 0.5;
  }
}

function stepRain(windVec, dt) {
  const w = canvas.width / (window.devicePixelRatio||1);
  const h = canvas.height / (window.devicePixelRatio||1);
  for (const drop of rain) {
    drop.vx += (windVec.x * 0.6 - drop.vx) * dt * 2;
    drop.vy += (windVec.y * 0.6 + CFG.RAIN_SPEED - drop.vy) * dt * 2;
    drop.x += drop.vx * dt * 60;
    drop.y += drop.vy * dt * 60;
    if (drop.y > h + 50 || drop.x < -50 || drop.x > w + 50) {
      drop.x = Math.random() * w;
      drop.y = -Math.random() * 200 - 50;
      drop.vx = 0; drop.vy = CFG.RAIN_SPEED;
    }
  }
}

/* ============ RENDER ============ */
function render() {
  const w = canvas.width / (window.devicePixelRatio||1);
  const h = canvas.height / (window.devicePixelRatio||1);
  ctx.clearRect(0,0,w,h);

  // Sky gradient
  const skyGrad = ctx.createLinearGradient(0,0,0,h*0.6);
  skyGrad.addColorStop(0, '#0d1426');
  skyGrad.addColorStop(1, '#1a2332');
  ctx.fillStyle = skyGrad;
  ctx.fillRect(0,0,w,h*0.6);

  // Ground
  ctx.fillStyle = '#141a2a';
  ctx.fillRect(0, CFG.GROUND_Y_PIX, w, h - CFG.GROUND_Y_PIX);
  ctx.fillStyle = '#1e2738';
  ctx.fillRect(0, CFG.GROUND_Y_PIX, w, 4);

  // Rain
  ctx.strokeStyle = 'rgba(137,180,250,0.4)';
  ctx.lineWidth = 0.8;
  ctx.lineCap = 'round';
  ctx.beginPath();
  for (const drop of rain) {
    ctx.moveTo(drop.x, drop.y);
    ctx.lineTo(drop.x - drop.vx*0.02, drop.y - drop.vy*0.02);
  }
  ctx.stroke();

  if (!umbrellaFree) {
    drawPerson();
    drawUmbrella();
  } else {
    drawFreeUmbrella();
  }

  // Wind indicator
  drawWindArrow(w, h);
}

function drawPerson() {
  ctx.save();
  ctx.translate(shoulder.x, shoulder.y);
  ctx.rotate(torsoAngle);

  // Legs
  const legLen = CFG.TORSO_LEN * CFG.SCALE * 1.1;
  const footY = CFG.GROUND_Y_PIX - shoulder.y;
  // Left leg
  ctx.beginPath();
  ctx.moveTo(footL.x * CFG.SCALE, 0);
  ctx.lineTo(footL.x * CFG.SCALE, footY * 0.55);
  ctx.lineTo(footL.x * CFG.SCALE, footY);
  ctx.strokeStyle = '#3a4a6b';
  ctx.lineWidth = 6;
  ctx.lineCap = 'round';
  ctx.stroke();
  // Right leg
  ctx.beginPath();
  ctx.moveTo(footR.x * CFG.SCALE, 0);
  ctx.lineTo(footR.x * CFG.SCALE, footY * 0.55);
  ctx.lineTo(footR.x * CFG.SCALE, footY);
  ctx.stroke();

  // Feet pressure indication
  ctx.fillStyle = `rgba(255,107,53,${0.3+heelPressure*0.5})`;
  ctx.beginPath(); ctx.arc(footL.x*CFG.SCALE, footY, 8, 0, Math.PI*2); ctx.fill();
  ctx.fillStyle = `rgba(78,205,196,${0.3+toePressure*0.5})`;
  ctx.beginPath(); ctx.arc(footR.x*CFG.SCALE, footY, 8, 0, Math.PI*2); ctx.fill();

  // Torso
  ctx.beginPath();
  ctx.moveTo(0,0);
  ctx.lineTo(0, CFG.TORSO_LEN * CFG.SCALE);
  ctx.strokeStyle = '#4a5a7a';
  ctx.lineWidth = 14;
  ctx.lineCap = 'round';
  ctx.stroke();

  // Arm IK
  const handTargetX = hub.x - shoulder.x;
  const handTargetY = hub.y - shoulder.y;
  const upperLen = CFG.UPPER_ARM * CFG.SCALE;
  const foreLen = CFG.FOREARM * CFG.SCALE;
  const dist = Math.hypot(handTargetX, handTargetY);
  let elbowAngle = 0, shoulderAngle = 0;
  if (dist > upperLen + foreLen - 5) {
    shoulderAngle = Math.atan2(handTargetY, handTargetX);
    elbowAngle = 0;
  } else if (dist < Math.abs(upperLen - foreLen) + 5) {
    shoulderAngle = Math.atan2(handTargetY, handTargetX);
    elbowAngle = Math.PI * 0.9;
  } else {
    const cosElbow = (upperLen*upperLen + foreLen*foreLen - dist*dist) / (2*upperLen*foreLen);
    elbowAngle = Math.acos(clamp(cosElbow, -1, 1));
    const angleToHand = Math.atan2(handTargetY, handTargetX);
    const cosShoulder = (upperLen*upperLen + dist*dist - foreLen*foreLen) / (2*upperLen*dist);
    shoulderAngle = angleToHand - Math.acos(clamp(cosShoulder, -1, 1));
  }

  // Upper arm
  ctx.beginPath();
  ctx.moveTo(0,0);
  ctx.lineTo(Math.cos(shoulderAngle)*upperLen, Math.sin(shoulderAngle)*upperLen);
  ctx.strokeStyle = '#5a6a8a';
  ctx.lineWidth = 10;
  ctx.stroke();

  // Forearm
  const elbowX = Math.cos(shoulderAngle)*upperLen;
  const elbowY = Math.sin(shoulderAngle)*upperLen;
  const forearmAngle = shoulderAngle + Math.PI - elbowAngle;
  ctx.beginPath();
  ctx.moveTo(elbowX, elbowY);
  ctx.lineTo(elbowX + Math.cos(forearmAngle)*foreLen, elbowY + Math.sin(forearmAngle)*foreLen);
  ctx.strokeStyle = '#6a7a9a';
  ctx.lineWidth = 8;
  ctx.stroke();

  // Hand (grip)
  const handX = elbowX + Math.cos(forearmAngle)*foreLen;
  const handY = elbowY + Math.sin(forearmAngle)*foreLen;
  ctx.fillStyle = '#c9b896';
  ctx.beginPath(); ctx.arc(handX, handY, 6, 0, Math.PI*2); ctx.fill();

  // Head
  ctx.fillStyle = '#d4c4a8';
  ctx.beginPath(); ctx.arc(0, -18, 16, 0, Math.PI*2); ctx.fill();

  ctx.restore();
}

function drawUmbrella() {
  // Shaft
  ctx.save();
  ctx.translate(hub.x, hub.y);
  ctx.rotate(shaft.angle);
  ctx.beginPath();
  ctx.moveTo(0,0);
  ctx.lineTo(0, -CFG.SHAFT_LENGTH * CFG.SCALE * 0.4);
  ctx.strokeStyle = '#2a3a5a';
  ctx.lineWidth = 4;
  ctx.lineCap = 'round';
  ctx.stroke();

  // Slider
  const sliderY = -CFG.SHAFT_LENGTH * CFG.SCALE * 0.4 * shaft.slider;
  ctx.fillStyle = '#3a4a6a';
  ctx.beginPath(); ctx.arc(0, sliderY, 5, 0, Math.PI*2); ctx.fill();

  // Ribs
  for (const rib of ribs) {
    const pts = rib.pts;
    ctx.beginPath();
    ctx.moveTo(pts[0].x - hub.x, pts[0].y - hub.y);
    for (let i=1;i<pts.length;i++) {
      ctx.lineTo(pts[i].x - hub.x, pts[i].y - hub.y);
    }
    ctx.strokeStyle = rib.inverted ? '#ff6b35' : '#4a5a7a';
    ctx.lineWidth = 2;
    ctx.stroke();

    // Membrane fill (triangulate to hub)
    if (!rib.inverted) {
      ctx.fillStyle = 'rgba(78,205,196,0.08)';
      ctx.beginPath();
      ctx.moveTo(hub.x, hub.y);
      for (let i=0;i<pts.length;i++) {
        ctx.lineTo(pts[i].x, pts[i].y);
      }
      ctx.closePath();
      ctx.fill();
    }
  }

  // Canopy membrane (between ribs)
  ctx.fillStyle = inverted ? 'rgba(255,107,53,0.15)' : 'rgba(78,205,196,0.12)';
  ctx.beginPath();
  for (let r=0;r<CFG.NUM_RIBS;r++) {
    const tip = ribs[r].pts[CFG.RIB_SEGS];
    if (r===0) ctx.moveTo(tip.x, tip.y);
    else ctx.lineTo(tip.x, tip.y);
  }
  ctx.closePath();
  ctx.fill();

  // Hub
  ctx.fillStyle = '#3a4a6a';
  ctx.beginPath(); ctx.arc(0,0, CFG.HUB_RADIUS*CFG.SCALE, 0, Math.PI*2); ctx.fill();

  ctx.restore();
}

function drawFreeUmbrella() {
  const b = umbrellaBody;
  ctx.save();
  ctx.translate(b.x, b.y);
  ctx.rotate(b.angle);
  // Simplified inverted canopy
  ctx.fillStyle = 'rgba(255,107,53,0.2)';
  ctx.beginPath();
  ctx.moveTo(0,0);
  for (let i=0;i<CFG.NUM_RIBS;i++) {
    const ang = (i/CFG.NUM_RIBS)*Math.PI*2;
    const r = CFG.CANOPY_RADIUS * CFG.SCALE * (inverted ? 1.2 : 1);
    ctx.lineTo(Math.cos(ang)*r, Math.sin(ang)*r);
  }
  ctx.closePath();
  ctx.fill();
  // Ribs
  ctx.strokeStyle = '#ff6b35';
  ctx.lineWidth = 2;
  for (let i=0;i<CFG.NUM_RIBS;i++) {
    const ang = (i/CFG.NUM_RIBS)*Math.PI*2;
    const r = CFG.CANOPY_RADIUS * CFG.SCALE * 1.2;
    ctx.beginPath();
    ctx.moveTo(0,0);
    ctx.lineTo(Math.cos(ang)*r, Math.sin(ang)*r);
    ctx.stroke();
  }
  ctx.restore();
}

function drawWindArrow(w, h) {
  const x = w - 60, y = 60;
  const len = Math.min(40, windSpeed * 1.5);
  ctx.save();
  ctx.translate(x, y);
  ctx.rotate(Math.atan2(-windSpeed*0.08, windSpeed));
  ctx.strokeStyle = `rgba(255,107,53,${0.5+windSpeed/70})`;
  ctx.lineWidth = 3;
  ctx.lineCap = 'round';
  ctx.beginPath();
  ctx.moveTo(-len, 0);
  ctx.lineTo(len, 0);
  ctx.stroke();
  // Arrowhead
  ctx.beginPath();
  ctx.moveTo(len, 0);
  ctx.lineTo(len-10, -6);
  ctx.lineTo(len-10, 6);
  ctx.closePath();
  ctx.fillStyle = ctx.strokeStyle;
  ctx.fill();
  ctx.restore();
  // Label
  ctx.fillStyle = 'rgba(255,255,255,0.6)';
  ctx.font = '11px system-ui';
  ctx.textAlign = 'center';
  ctx.fillText(`${windSpeed.toFixed(1)} m/s`, x, y - len - 8);
}

/* ============ LOOP ============ */
function loop(ts) {
  if (!lastTime) lastTime = ts;
  const dt = Math.min((ts - lastTime) / 1000, 0.05);
  lastTime = ts;
  step(dt);
  render();
  requestAnimationFrame(loop);
}

/* ============ INPUT ============ */
windSlider.addEventListener('input', e => {
  targetWind = parseFloat(e.target.value) / 100 * CFG.MAX_WIND;
  autoRamp = false;
});
window.addEventListener('keydown', e => {
  keys[e.key] = true;
  if (e.key === 'ArrowRight' || e.key === 'd' || e.key === 'D') {
    targetWind = Math.min(CFG.MAX_WIND, targetWind + 1.5);
    windSlider.value = Math.round(targetWind / CFG.MAX_WIND * 100);
    autoRamp = false;
  } else if (e.key === 'ArrowLeft' || e.key === 'a' || e.key === 'A') {
    targetWind = Math.max(0, targetWind - 1.5);
    windSlider.value = Math.round(targetWind / CFG.MAX_WIND * 100);
    autoRamp = false;
  } else if (e.key === ' ') {
    autoRamp = !autoRamp;
    e.preventDefault();
  } else if (e.key === 'r' || e.key === 'R') {
    initUmbrella();
    targetWind = 0;
    windSlider.value = 0;
    autoRamp = false;
  }
});
window.addEventListener('keyup', e => { keys[e.key] = false; });
window.addEventListener('resize', resize);

/* ============ UTIL ============ */
function clamp(v, a, b) { return Math.max(a, Math.min(b, v)); }

/* ============ START ============ */
resize();
requestAnimationFrame(loop);
</script>
</body>
</html>

What it actually does

Where it looks right:

The canopy ribs flex realistically under load — you see the tips lift first, then the whole dome balloons before snapping inside-out. The inversion threshold feels about right: sustained ~18 m/s with the slider, or a sharp gust past 22 m/s, triggers the buckle.
Rain streaks tilt and accelerate with the wind vector; you can watch drops go horizontal in a gale.
The person leans into it properly: torso angle tracks wind force with a damped spring, feet show heel/toe pressure shift, and the arm IK reaches for the sliding grip point on the shaft.
Grip failure is dramatic — the umbrella doesn't just vanish, it becomes a free body that tumbles, drags, and skitters along the ground.
Auto-ramp (Space) gives a nice "storm approaching" feel; keyboard control is responsive.

Where it looks wrong:

Membrane behavior is too stiff. Real nylon stretches and flaps; mine holds a smooth curved surface until inversion, then just extends rest lengths. No flutter, no panel snap-through.
Rib bending is oversimplified. Real ribs have a slider that moves up the shaft, changing the canopy curvature. I fake it with a fixed hub and angle constraints — so the canopy doesn't "pump" open/closed as wind pulses.
Inversion is binary. A real umbrella inverts panel-by-panel, often asymmetrically. Mine flips all 12 ribs simultaneously once the mean angle crosses threshold.
No fabric porosity. Wind doesn't bleed through; the drag coefficient is constant. Real umbrellas vent at the apex, reducing peak load.
Person has no upper-body compliance. Shoulders don't roll, spine doesn't twist, grip doesn't fatigue. The arm IK sometimes snaps when the hand target moves faster than the two-link chain can reach.
Free umbrella physics is cartoonish. It tumbles with constant drag, no autorotation, no ground bounce realism. It should cartwheel downwind.
Rain doesn't interact with canopy. Drops fall through the membrane; no splash, no runoff, no weight loading.
Wind field is uniform. No gust structure, no shear, no turbulence — just a scalar that ramps.

Attachments

nvidia/nemotron-3-ultra-550b-a55b:free — page