<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      background: #ffffff;
      padding: 12px;
      display: flex;
      flex-direction: column;
      gap: 10px;
      width: 100%;
      height: 100%;
      user-select: none;
    }

    /* Stepper Controls */
    .controls {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 6px;
    }
    .steps {
      display: flex;
      gap: 6px;
      flex: 1;
    }
    .step-btn {
      flex: 1;
      padding: 6px 4px;
      font-size: 13px;
      font-weight: 600;
      border: 1px solid #e2e8f0;
      background: #f8fafc;
      border-radius: 8px;
      cursor: pointer;
      color: #64748b;
      transition: all 0.25s ease;
      text-align: center;
      white-space: nowrap;
    }
    .step-btn.active {
      background: #eff6ff;
      border-color: #3b82f6;
      color: #1d4ed8;
      box-shadow: 0 1px 3px rgba(59, 130, 246, 0.15);
    }
    .play-btn {
      width: 32px;
      height: 32px;
      display: flex;
      align-items: center;
      justify-content: center;
      border: 1px solid #e2e8f0;
      background: #f8fafc;
      border-radius: 8px;
      cursor: pointer;
      font-size: 14px;
      color: #475569;
    }

    /* Syringe Chamber */
    .syringe-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }
    .chamber-wrapper {
      position: relative;
      height: 140px;
      width: 100%;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .syringe-svg {
      width: 100%;
      height: 100%;
      overflow: visible;
    }
    .gas-fill {
      transition: fill 0.6s ease;
    }
    .molecule {
      transition: all 0.6s ease;
    }

    /* Dynamic Rates & Concentration Dashboards */
    .dashboard {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
    }
    .panel {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 10px;
      display: flex;
      flex-direction: column;
      gap: 6px;
    }
    .panel-title {
      font-size: 12px;
      font-weight: 700;
      color: #475569;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }
    
    /* Concentration Bars */
    .meter-row {
      display: flex;
      align-items: center;
      gap: 6px;
      font-size: 13px;
      font-weight: 600;
    }
    .meter-label {
      width: 52px;
      font-size: 12px;
    }
    .bar-track {
      flex: 1;
      height: 10px;
      background: #e2e8f0;
      border-radius: 5px;
      overflow: hidden;
    }
    .bar-fill {
      height: 100%;
      border-radius: 5px;
      transition: width 0.5s ease;
    }
    .fill-n2o4 { background: #3b82f6; }
    .fill-no2 { background: #d97706; }

    /* Reaction Rates Balance */
    .rate-row {
      display: flex;
      flex-direction: column;
      gap: 4px;
    }
    .rate-bar-container {
      display: flex;
      align-items: center;
      gap: 6px;
      font-size: 12px;
    }
    .rate-track {
      flex: 1;
      height: 8px;
      background: #e2e8f0;
      border-radius: 4px;
      overflow: hidden;
    }
    .rate-fill {
      height: 100%;
      border-radius: 4px;
      transition: width 0.5s ease;
    }
    .fwd-fill { background: #059669; }
    .rev-fill { background: #8b5cf6; }

    /* State Status Badge */
    .status-banner {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 13px;
      font-weight: 700;
      padding: 6px 10px;
      border-radius: 8px;
      background: #f1f5f9;
      color: #334155;
      transition: all 0.3s ease;
      text-align: center;
    }
    .status-banner.eq {
      background: #ecfdf5;
      color: #065f46;
      border: 1px solid #a7f3d0;
    }

    /* Molecule Legend */
    .legend {
      display: flex;
      justify-content: center;
      gap: 14px;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
    }
    .legend-item {
      display: flex;
      align-items: center;
      gap: 5px;
    }
    .dot-n2o4 {
      width: 16px;
      height: 9px;
      background: #3b82f6;
      border-radius: 5px;
      border: 1px solid #1d4ed8;
    }
    .dot-no2 {
      width: 9px;
      height: 9px;
      background: #d97706;
      border-radius: 50%;
      border: 1px solid #b45309;
    }
  </style>
</head>
<body>

  
  <div class="controls">
    <div class="steps">
      <button class="step-btn active" onclick="setStep(0)">1. Initial</button>
      <button class="step-btn" onclick="setStep(1)">2. Reacting</button>
      <button class="step-btn" onclick="setStep(2)">3. Equilibrium</button>
    </div>
    <button class="play-btn" id="playBtn" onclick="togglePlay()" title="Play/Pause">⏸</button>
  </div>

  
  <div class="syringe-card">
    <div class="chamber-wrapper">
      <svg class="syringe-svg" viewBox="0 0 340 120">
        <defs>
          
          <g id="mol-n2o4">
            <ellipse cx="0" cy="0" rx="8" ry="4.5" fill="#3b82f6" stroke="#1d4ed8" stroke-width="1.2"/>
            <circle cx="-4" cy="0" r="2.5" fill="#93c5fd"/>
            <circle cx="4" cy="0" r="2.5" fill="#93c5fd"/>
          </g>
          <g id="mol-no2">
            <circle cx="0" cy="0" r="4.5" fill="#d97706" stroke="#b45309" stroke-width="1.2"/>
            <circle cx="0" cy="0" r="2" fill="#fde68a"/>
          </g>
        </defs>

        
        <rect x="18" y="52" width="12" height="16" rx="2" fill="#64748b" stroke="#334155" stroke-width="1.5"/>
        <line x1="18" y1="60" x2="14" y2="60" stroke="#ef4444" stroke-width="3" stroke-linecap="round"/>
        <circle cx="14" cy="60" r="2.5" fill="#ef4444"/>

        
        <rect id="gasColor" class="gas-fill" x="30" y="24" width="220" height="72" rx="2" fill="#f8fafc"/>

        
        <g stroke="#cbd5e1" stroke-width="1">
          <line x1="74" y1="24" x2="74" y2="34"/>
          <line x1="118" y1="24" x2="118" y2="34"/>
          <line x1="162" y1="24" x2="162" y2="34"/>
          <line x1="206" y1="24" x2="206" y2="34"/>
        </g>

        
        <rect x="30" y="24" width="220" height="72" rx="4" fill="none" stroke="#94a3b8" stroke-width="2.5"/>
        <rect x="246" y="16" width="8" height="88" rx="2" fill="#94a3b8"/>

        
        <g transform="translate(0, 0)">
          <rect x="236" y="26" width="14" height="68" rx="2" fill="#475569" stroke="#1e293b" stroke-width="1.5"/>
          <rect x="250" y="54" width="65" height="12" fill="#64748b" stroke="#334155" stroke-width="1.5"/>
          <rect x="315" y="42" width="8" height="36" rx="2" fill="#475569" stroke="#1e293b" stroke-width="1.5"/>
        </g>

        
        <g id="moleculesGroup"></g>

        
        <g id="eqArrows" opacity="0" style="transition: opacity 0.4s ease;">
          <text x="140" y="112" font-size="11" font-weight="700" fill="#059669" text-anchor="middle">⇌ Continuous Equal Exchange</text>
        </g>
      </svg>
    </div>

    
    <div class="legend">
      <div class="legend-item"><div class="dot-n2o4"></div> N₂O₄ (Colorless)</div>
      <div class="legend-item"><div class="dot-no2"></div> NO₂ (Brown)</div>
    </div>
  </div>

  
  <div class="dashboard">
    
    <div class="panel">
      <div class="panel-title">Concentration</div>
      <div class="meter-row">
        <div class="meter-label">[N₂O₄]</div>
        <div class="bar-track">
          <div id="barN2O4" class="bar-fill fill-n2o4" style="width: 100%;"></div>
        </div>
      </div>
      <div class="meter-row">
        <div class="meter-label">[NO₂]</div>
        <div class="bar-track">
          <div id="barNO2" class="bar-fill fill-no2" style="width: 0%;"></div>
        </div>
      </div>
    </div>

    
    <div class="panel">
      <div class="panel-title">Reaction Rates</div>
      <div class="rate-row">
        <div class="rate-bar-container">
          <span style="width: 50px; font-weight:600;">Forward</span>
          <div class="rate-track">
            <div id="rateFwd" class="rate-fill fwd-fill" style="width: 90%;"></div>
          </div>
        </div>
        <div class="rate-bar-container">
          <span style="width: 50px; font-weight:600;">Reverse</span>
          <div class="rate-track">
            <div id="rateRev" class="rate-fill rev-fill" style="width: 0%;"></div>
          </div>
        </div>
      </div>
    </div>
  </div>

  
  <div id="statusBanner" class="status-banner">
    Initial: Pure Colorless N₂O₄
  </div>

  <script>
    const stepsData = [
      {
        gasColor: "#f8fafc",
        n2o4: 8,
        no2: 0,
        concN2O4: "100%",
        concNO2: "0%",
        rateFwd: "95%",
        rateRev: "0%",
        status: "Stage 1: Pure N₂O₄ (Colorless)",
        isEq: false
      },
      {
        gasColor: "rgba(217, 119, 6, 0.18)",
        n2o4: 5,
        no2: 6,
        concN2O4: "62%",
        concNO2: "45%",
        rateFwd: "65%",
        rateRev: "35%",
        status: "Stage 2: Reaction in Progress (Light Tan)",
        isEq: false
      },
      {
        gasColor: "rgba(217, 119, 6, 0.42)",
        n2o4: 4,
        no2: 8,
        concN2O4: "50%",
        concNO2: "50%",
        rateFwd: "50%",
        rateRev: "50%",
        status: "Stage 3: Equilibrium (Forward Rate = Reverse Rate)",
        isEq: true
      }
    ];

    // Predefined positions inside syringe chamber: x in [45, 220], y in [35, 85]
    const posN2O4 = [
      {x: 60, y: 45}, {x: 105, y: 75}, {x: 150, y: 42}, {x: 195, y: 72},
      {x: 80, y: 75}, {x: 125, y: 48}, {x: 170, y: 78}, {x: 215, y: 45}
    ];

    const posNO2 = [
      {x: 50, y: 75}, {x: 70, y: 40},
      {x: 95, y: 50}, {x: 115, y: 80},
      {x: 140, y: 75}, {x: 160, y: 45},
      {x: 185, y: 50}, {x: 205, y: 78}
    ];

    let currentStep = 0;
    let timer = null;
    let isPlaying = true;

    function renderMolecules(stepIndex) {
      const g = document.getElementById('moleculesGroup');
      g.innerHTML = '';
      const data = stepsData[stepIndex];

      // Render N2O4 molecules
      for (let i = 0; i < data.n2o4; i++) {
        const p = posN2O4[i];
        const use = document.createElementNS('http://www.w3.org/2000/svg', 'use');
        use.setAttribute('href', '#mol-n2o4');
        use.setAttribute('x', p.x);
        use.setAttribute('y', p.y);
        use.setAttribute('class', 'molecule');
        g.appendChild(use);
      }

      // Render NO2 molecules
      for (let i = 0; i < data.no2; i++) {
        const p = posNO2[i];
        const use = document.createElementNS('http://www.w3.org/2000/svg', 'use');
        use.setAttribute('href', '#mol-no2');
        use.setAttribute('x', p.x);
        use.setAttribute('y', p.y);
        use.setAttribute('class', 'molecule');
        g.appendChild(use);
      }
    }

    function setStep(index) {
      currentStep = index;
      const data = stepsData[index];

      // Update buttons
      document.querySelectorAll('.step-btn').forEach((btn, i) => {
        btn.classList.toggle('active', i === index);
      });

      // Update Syringe gas color
      document.getElementById('gasColor').setAttribute('fill', data.gasColor);
      document.getElementById('eqArrows').style.opacity = data.isEq ? "1" : "0";

      // Render molecules
      renderMolecules(index);

      // Update dashboard meters
      document.getElementById('barN2O4').style.width = data.concN2O4;
      document.getElementById('barNO2').style.width = data.concNO2;
      document.getElementById('rateFwd').style.width = data.rateFwd;
      document.getElementById('rateRev').style.width = data.rateRev;

      // Update Status Badge
      const banner = document.getElementById('statusBanner');
      banner.textContent = data.status;
      banner.classList.toggle('eq', data.isEq);
    }

    function nextStep() {
      const next = (currentStep + 1) % stepsData.length;
      setStep(next);
    }

    function startAutoPlay() {
      if (timer) clearInterval(timer);
      timer = setInterval(nextStep, 3500);
      isPlaying = true;
      document.getElementById('playBtn').textContent = '⏸';
    }

    function pauseAutoPlay() {
      if (timer) clearInterval(timer);
      timer = null;
      isPlaying = false;
      document.getElementById('playBtn').textContent = '▶';
    }

    function togglePlay() {
      if (isPlaying) {
        pauseAutoPlay();
      } else {
        nextStep();
        startAutoPlay();
      }
    }

    // Init
    setStep(0);
    startAutoPlay();
  </script>
</body>
</html>

Dynamic Equilibrium and Le Chatelier's Principle

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <title>Dynamic Equilibrium in a Closed System</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #f8f9fa;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 10px;
      user-select: none;
    }

    /* Status Banner */
    .banner {
      width: 100%;
      max-width: 440px;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 10px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      font-size: 13px;
      font-weight: 600;
      color: #1e2945;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }
    .badge-lock {
      background: #e0f2fe;
      color: #0284c7;
      padding: 2px 6px;
      border-radius: 4px;
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
    }

    /* Main Flask Container */
    .stage {
      position: relative;
      width: 100%;
      max-width: 440px;
      height: 250px;
      background: #ffffff;
      border-radius: 12px;
      border: 1px solid #e2e8f0;
      display: flex;
      justify-content: center;
      align-items: center;
      overflow: hidden;
    }

    canvas {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
    }

    /* Reaction Indicator overlay */
    .rxn-pill {
      position: absolute;
      top: 10px;
      background: rgba(255, 255, 255, 0.92);
      backdrop-filter: blur(4px);
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      padding: 4px 12px;
      display: flex;
      align-items: center;
      gap: 8px;
      font-size: 14px;
      font-weight: 700;
      box-shadow: 0 2px 6px rgba(0,0,0,0.06);
      z-index: 5;
    }
    .dot-a {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      background: #22b7ff;
      display: inline-block;
    }
    .dot-b {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      background: #f59e0b;
      display: inline-block;
    }

    /* Rate Counter Dashboard */
    .dashboard {
      width: 100%;
      max-width: 440px;
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
    }

    .rate-card {
      background: #ffffff;
      border-radius: 10px;
      padding: 8px 10px;
      border: 1px solid #e2e8f0;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 2px;
      box-shadow: 0 1px 2px rgba(0,0,0,0.03);
    }
    .rate-card.forward {
      border-top: 3px solid #22b7ff;
    }
    .rate-card.reverse {
      border-top: 3px solid #f59e0b;
    }
    .rate-title {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
      display: flex;
      align-items: center;
      gap: 4px;
    }
    .rate-val {
      font-size: 15px;
      font-weight: 800;
      color: #1e2945;
    }

    /* Controls */
    .controls {
      width: 100%;
      max-width: 440px;
      display: flex;
      justify-content: center;
      gap: 8px;
    }
    .btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 6px 14px;
      font-size: 12px;
      font-weight: 600;
      color: #1e2945;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 6px;
    }
    .btn:hover {
      background: #f1f5f9;
    }
    .btn:active {
      background: #e2e8f0;
    }
  </style>
</head>
<body>

  
  <div class="banner">
    <span class="badge-lock">Sealed</span>
    <span>Closed System: No matter enters or leaves</span>
  </div>

  
  <div class="stage">
    <div class="rxn-pill">
      <span class="dot-a"></span>
      <span style="color:#0284c7">A</span>
      <span style="color:#64748b; font-size:16px;">⇄</span>
      <span style="color:#d97706">B</span>
      <span class="dot-b"></span>
    </div>
    <canvas id="chemCanvas"></canvas>
  </div>

  
  <div class="dashboard">
    <div class="rate-card forward">
      <div class="rate-title">
        <span class="dot-a"></span> Forward Rate (A → B)
      </div>
      <div class="rate-val" id="fwdRate">4 mol/s</div>
    </div>
    <div class="rate-card reverse">
      <div class="rate-title">
        <span class="dot-b"></span> Reverse Rate (B → A)
      </div>
      <div class="rate-val" id="revRate">4 mol/s</div>
    </div>
  </div>

  
  <div class="controls">
    <button class="btn" id="playBtn">⏸ Pause</button>
    <button class="btn" id="rateBtn">Rate: Normal (4 mol/s)</button>
  </div>

  <script>
    const canvas = document.getElementById('chemCanvas');
    const ctx = canvas.getContext('2d');
    const playBtn = document.getElementById('playBtn');
    const rateBtn = document.getElementById('rateBtn');
    const fwdRateEl = document.getElementById('fwdRate');
    const revRateEl = document.getElementById('revRate');

    let width, height;
    let isPlaying = true;
    let currentRate = 4; // mol/s baseline

    function resize() {
      const rect = canvas.getBoundingClientRect();
      width = rect.width;
      height = rect.height;
      canvas.width = width * window.devicePixelRatio;
      canvas.height = height * window.devicePixelRatio;
      ctx.scale(window.devicePixelRatio, window.devicePixelRatio);
    }
    window.addEventListener('resize', resize);
    resize();

    // Particle Simulation
    const PARTICLE_COUNT = 28;
    const particles = [];

    class Particle {
      constructor(type) {
        this.type = type; // 'A' (blue) or 'B' (amber)
        this.r = 7;
        this.x = Math.random() * (width - 60) + 30;
        this.y = Math.random() * (height - 80) + 50;
        const angle = Math.random() * Math.PI * 2;
        const speed = 1.2 + Math.random() * 0.8;
        this.vx = Math.cos(angle) * speed;
        this.vy = Math.sin(angle) * speed;
        this.flash = 0; // transformation effect
      }

      update() {
        this.x += this.vx;
        this.y += this.vy;

        // Bounce within flask boundaries (padded)
        const minX = 25, maxX = width - 25;
        const minY = 45, maxY = height - 20;

        if (this.x < minX) { this.x = minX; this.vx *= -1; }
        if (this.x > maxX) { this.x = maxX; this.vx *= -1; }
        if (this.y < minY) { this.y = minY; this.vy *= -1; }
        if (this.y > maxY) { this.y = maxY; this.vy *= -1; }

        if (this.flash > 0) this.flash -= 0.04;
      }

      draw() {
        ctx.save();
        ctx.beginPath();
        ctx.arc(this.x, this.y, this.r, 0, Math.PI * 2);
        ctx.fillStyle = this.type === 'A' ? '#22b7ff' : '#f59e0b';
        ctx.fill();

        // Transformation halo/glow
        if (this.flash > 0) {
          ctx.beginPath();
          ctx.arc(this.x, this.y, this.r + 6 * (1 - this.flash), 0, Math.PI * 2);
          ctx.strokeStyle = this.type === 'A' ? `rgba(34, 183, 255, ${this.flash})` : `rgba(245, 158, 11, ${this.flash})`;
          ctx.lineWidth = 2.5;
          ctx.stroke();
        }

        ctx.restore();
      }
    }

    // Initialize 50% A and 50% B
    for (let i = 0; i < PARTICLE_COUNT; i++) {
      particles.push(new Particle(i % 2 === 0 ? 'A' : 'B'));
    }

    // Reaction Conversion Timer (Dynamic Equilibrium: equal rates)
    let lastConversion = Date.now();

    function triggerConversions() {
      const now = Date.now();
      const interval = 1000 / currentRate; // ms per conversion

      if (now - lastConversion >= interval) {
        lastConversion = now;

        // Convert one A -> B
        const aList = particles.filter(p => p.type === 'A');
        if (aList.length > 0) {
          const pA = aList[Math.floor(Math.random() * aList.length)];
          pA.type = 'B';
          pA.flash = 1;
        }

        // Convert one B -> A (at exact same rate)
        const bList = particles.filter(p => p.type === 'B');
        if (bList.length > 0) {
          const pB = bList[Math.floor(Math.random() * bList.length)];
          pB.type = 'A';
          pB.flash = 1;
        }
      }
    }

    function drawFlaskOutline() {
      ctx.save();
      ctx.strokeStyle = '#cbd5e1';
      ctx.lineWidth = 2;
      ctx.fillStyle = 'rgba(241, 245, 249, 0.4)';

      // Flask rounded chamber
      ctx.beginPath();
      ctx.roundRect(16, 38, width - 32, height - 50, 16);
      ctx.fill();
      ctx.stroke();

      // Top stopper
      ctx.fillStyle = '#94a3b8';
      ctx.beginPath();
      ctx.roundRect(width / 2 - 24, 28, 48, 12, 4);
      ctx.fill();

      ctx.restore();
    }

    function animate() {
      if (isPlaying) {
        ctx.clearRect(0, 0, width, height);
        drawFlaskOutline();

        triggerConversions();

        for (let p of particles) {
          p.update();
          p.draw();
        }
      }
      requestAnimationFrame(animate);
    }
    animate();

    // Event Listeners
    playBtn.addEventListener('click', () => {
      isPlaying = !isPlaying;
      playBtn.textContent = isPlaying ? '⏸ Pause' : '▶ Play';
    });

    const rates = [
      { val: 2, label: 'Rate: Slow (2 mol/s)' },
      { val: 4, label: 'Rate: Normal (4 mol/s)' },
      { val: 6, label: 'Rate: Fast (6 mol/s)' }
    ];
    let rateIdx = 1;

    rateBtn.addEventListener('click', () => {
      rateIdx = (rateIdx + 1) % rates.length;
      currentRate = rates[rateIdx].val;
      rateBtn.textContent = rates[rateIdx].label;
      fwdRateEl.textContent = `${currentRate} mol/s`;
      revRateEl.textContent = `${currentRate} mol/s`;
    });
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      color: #1e2945;
      background: #ffffff;
      padding: 12px;
    }
    .header-eq {
      text-align: center;
      font-weight: 700;
      font-size: 15px;
      margin-bottom: 12px;
      letter-spacing: 0.5px;
    }
    .eq-blue { color: #2563eb; }
    .eq-brown { color: #b45309; }
    .comparison-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
    }
    @media (max-width: 420px) {
      .comparison-grid {
        grid-template-columns: 1fr;
      }
    }
    .system-card {
      border: 1px solid #e6e6e6;
      border-radius: 10px;
      padding: 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      background: #fafafa;
    }
    .system-title {
      font-weight: 700;
      font-size: 14px;
      margin-bottom: 6px;
    }
    .badge {
      font-size: 11px;
      font-weight: 600;
      padding: 4px 8px;
      border-radius: 6px;
      text-align: center;
      margin-bottom: 8px;
      width: 100%;
    }
    .badge-red {
      background: #fee2e2;
      color: #b91c1c;
      border: 1px solid #fecaca;
    }
    .badge-green {
      background: #dcfce7;
      color: #15803d;
      border: 1px solid #bbf7d0;
    }
    .canvas-box {
      width: 100%;
      height: 180px;
      position: relative;
      background: #ffffff;
      border-radius: 8px;
      border: 1px solid #e6e6e6;
      overflow: hidden;
    }
    canvas {
      width: 100%;
      height: 100%;
      display: block;
    }
    .controls {
      display: flex;
      justify-content: center;
      gap: 8px;
      margin-top: 10px;
    }
    .btn {
      background: #ffffff;
      border: 1px solid #d1d5db;
      border-radius: 6px;
      padding: 6px 12px;
      font-size: 12px;
      font-weight: 600;
      color: #1e2945;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 4px;
    }
    .btn:active {
      background: #f3f4f6;
    }
    .legend {
      display: flex;
      justify-content: center;
      gap: 16px;
      margin-top: 10px;
      font-size: 12px;
      font-weight: 600;
    }
    .legend-item {
      display: flex;
      align-items: center;
      gap: 6px;
    }
    .dot-n2o4 {
      width: 16px;
      height: 10px;
      background: #3b82f6;
      border-radius: 5px;
      border: 1px solid #1d4ed8;
    }
    .dot-no2 {
      width: 10px;
      height: 10px;
      background: #d97706;
      border-radius: 50%;
      border: 1px solid #b45309;
    }
  </style>
</head>
<body>

  <div class="header-eq">
    <span class="eq-blue">N₂O₄</span> (colorless) ⇌ 2 <span class="eq-brown">NO₂</span> (brown)
  </div>

  <div class="comparison-grid">
    
    <div class="system-card">
      <div class="system-title">Open Beaker</div>
      <div class="badge badge-red">No Equilibrium - Matter Escapes</div>
      <div class="canvas-box">
        <canvas id="openCanvas"></canvas>
      </div>
    </div>

    
    <div class="system-card">
      <div class="system-title">Sealed Flask</div>
      <div class="badge badge-green">Closed System - Matter Contained</div>
      <div class="canvas-box">
        <canvas id="closedCanvas"></canvas>
      </div>
    </div>
  </div>

  <div class="legend">
    <div class="legend-item"><div class="dot-n2o4"></div> N₂O₄ (Paired)</div>
    <div class="legend-item"><div class="dot-no2"></div> NO₂ (Single)</div>
  </div>

  <div class="controls">
    <button class="btn" id="toggleStateBtn">⇌ Reaction Active</button>
  </div>

  <script>
    const openCanvas = document.getElementById('openCanvas');
    const closedCanvas = document.getElementById('closedCanvas');
    const openCtx = openCanvas.getContext('2d');
    const closedCtx = closedCanvas.getContext('2d');
    const toggleBtn = document.getElementById('toggleStateBtn');

    let active = true;

    function resizeCanvas(canvas) {
      const rect = canvas.getBoundingClientRect();
      const dpr = window.devicePixelRatio || 1;
      canvas.width = rect.width * dpr;
      canvas.height = rect.height * dpr;
      const ctx = canvas.getContext('2d');
      ctx.resetTransform?.();
      ctx.scale(dpr, dpr);
      return { width: rect.width, height: rect.height };
    }

    let openDim = { width: 150, height: 180 };
    let closedDim = { width: 150, height: 180 };

    function handleResize() {
      openDim = resizeCanvas(openCanvas);
      closedDim = resizeCanvas(closedCanvas);
    }
    window.addEventListener('resize', handleResize);
    handleResize();

    // Open System Particles: NO2 escaping constantly
    let openParticles = [];
    function spawnOpenParticle() {
      const x = openDim.width * 0.25 + Math.random() * (openDim.width * 0.5);
      const y = openDim.height * 0.75;
      openParticles.push({
        x: x,
        y: y,
        vx: (Math.random() - 0.5) * 0.8,
        vy: -0.9 - Math.random() * 0.8,
        life: 1.0,
        type: 'no2'
      });
    }

    // Closed System Particles: mixture in dynamic equilibrium
    let closedParticles = [];
    function initClosedParticles() {
      closedParticles = [];
      // 4 N2O4 molecules (paired)
      for (let i = 0; i < 4; i++) {
        closedParticles.push({
          x: closedDim.width * 0.3 + Math.random() * (closedDim.width * 0.4),
          y: closedDim.height * 0.35 + Math.random() * (closedDim.height * 0.45),
          vx: (Math.random() - 0.5) * 1.2,
          vy: (Math.random() - 0.5) * 1.2,
          type: 'n2o4',
          timer: Math.random() * 200
        });
      }
      // 6 NO2 molecules (single)
      for (let i = 0; i < 6; i++) {
        closedParticles.push({
          x: closedDim.width * 0.3 + Math.random() * (closedDim.width * 0.4),
          y: closedDim.height * 0.35 + Math.random() * (closedDim.height * 0.45),
          vx: (Math.random() - 0.5) * 1.5,
          vy: (Math.random() - 0.5) * 1.5,
          type: 'no2',
          timer: Math.random() * 200
        });
      }
    }
    initClosedParticles();

    toggleBtn.addEventListener('click', () => {
      active = !active;
      toggleBtn.textContent = active ? '⇌ Reaction Active' : '⏸ Paused';
    });

    let frameCount = 0;

    function render() {
      frameCount++;

      // --- OPEN SYSTEM ---
      openCtx.clearRect(0, 0, openDim.width, openDim.height);
      
      // Draw open beaker
      const bx = openDim.width * 0.2;
      const bw = openDim.width * 0.6;
      const by = openDim.height * 0.4;
      const bh = openDim.height * 0.5;
      
      openCtx.strokeStyle = '#94a3b8';
      openCtx.lineWidth = 2.5;
      openCtx.lineCap = 'round';
      openCtx.beginPath();
      openCtx.moveTo(bx - 4, by);
      openCtx.lineTo(bx, by);
      openCtx.lineTo(bx, by + bh);
      openCtx.lineTo(bx + bw, by + bh);
      openCtx.lineTo(bx + bw, by);
      openCtx.lineTo(bx + bw + 4, by);
      openCtx.stroke();

      if (active && frameCount % 12 === 0 && openParticles.length < 20) {
        spawnOpenParticle();
      }

      // Update & render open particles
      for (let i = openParticles.length - 1; i >= 0; i--) {
        const p = openParticles[i];
        if (active) {
          p.x += p.vx;
          p.y += p.vy;
          if (p.y < by) {
            p.life -= 0.015;
          }
        }
        
        openCtx.save();
        openCtx.globalAlpha = Math.max(0, p.life);
        openCtx.fillStyle = '#d97706';
        openCtx.strokeStyle = '#b45309';
        openCtx.lineWidth = 1;
        openCtx.beginPath();
        openCtx.arc(p.x, p.y, 4, 0, Math.PI * 2);
        openCtx.fill();
        openCtx.stroke();
        openCtx.restore();

        if (p.life <= 0 || p.y < 5) {
          openParticles.splice(i, 1);
        }
      }

      // --- CLOSED SYSTEM ---
      closedCtx.clearRect(0, 0, closedDim.width, closedDim.height);

      // Draw sealed flask with stopper
      const cx = closedDim.width * 0.2;
      const cw = closedDim.width * 0.6;
      const cy = closedDim.height * 0.4;
      const ch = closedDim.height * 0.5;

      closedCtx.strokeStyle = '#94a3b8';
      closedCtx.lineWidth = 2.5;
      closedCtx.beginPath();
      // Flask neck and body
      closedCtx.moveTo(cx + cw * 0.35, cy - 15);
      closedCtx.lineTo(cx + cw * 0.35, cy);
      closedCtx.lineTo(cx, cy + ch);
      closedCtx.lineTo(cx + cw, cy + ch);
      closedCtx.lineTo(cx + cw * 0.65, cy);
      closedCtx.lineTo(cx + cw * 0.65, cy - 15);
      closedCtx.stroke();

      // Stopper
      closedCtx.fillStyle = '#64748b';
      closedCtx.fillRect(cx + cw * 0.33, cy - 20, cw * 0.34, 8);

      const minX = cx + 8;
      const maxX = cx + cw - 8;
      const minY = cy + 10;
      const maxY = cy + ch - 6;

      // Update and draw closed particles
      closedParticles.forEach((p, idx) => {
        if (active) {
          p.x += p.vx;
          p.y += p.vy;

          if (p.x <= minX) { p.x = minX; p.vx *= -1; }
          if (p.x >= maxX) { p.x = maxX; p.vx *= -1; }
          if (p.y <= minY) { p.y = minY; p.vy *= -1; }
          if (p.y >= maxY) { p.y = maxY; p.vy *= -1; }

          p.timer++;
          // Dynamic conversion back and forth
          if (p.timer > 300) {
            p.timer = 0;
            if (p.type === 'n2o4') {
              p.type = 'no2';
            } else {
              p.type = 'n2o4';
            }
          }
        }

        if (p.type === 'n2o4') {
          // Paired blue sphere (N2O4)
          closedCtx.fillStyle = '#3b82f6';
          closedCtx.strokeStyle = '#1d4ed8';
          closedCtx.lineWidth = 1;
          
          closedCtx.beginPath();
          closedCtx.arc(p.x - 3.5, p.y, 4, 0, Math.PI * 2);
          closedCtx.arc(p.x + 3.5, p.y, 4, 0, Math.PI * 2);
          closedCtx.fill();
          closedCtx.stroke();
        } else {
          // Single orange/brown sphere (NO2)
          closedCtx.fillStyle = '#d97706';
          closedCtx.strokeStyle = '#b45309';
          closedCtx.lineWidth = 1;
          
          closedCtx.beginPath();
          closedCtx.arc(p.x, p.y, 4, 0, Math.PI * 2);
          closedCtx.fill();
          closedCtx.stroke();
        }
      });

      requestAnimationFrame(render);
    }

    render();
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="16:9">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, sans-serif;
      background: transparent;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100vh;
      padding: 8px;
    }

    .container {
      width: 100%;
      max-width: 660px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    /* Controls Bar */
    .controls {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
      flex-wrap: wrap;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 12px;
    }

    .btn-group {
      display: flex;
      gap: 4px;
    }

    button {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 4px 10px;
      font-size: 13px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 4px;
      transition: background 0.2s, border-color 0.2s, color 0.2s;
    }

    button:hover {
      border-color: #94a3b8;
      background: #f1f5f9;
    }

    button.active {
      background: #22b7ff;
      border-color: #0284c7;
      color: #ffffff;
    }

    .slider-container {
      display: flex;
      align-items: center;
      gap: 8px;
      flex: 1;
      min-width: 140px;
      justify-content: flex-end;
    }

    .slider-label {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
      white-space: nowrap;
    }

    input[type="range"] {
      flex: 1;
      max-width: 130px;
      accent-color: #22b7ff;
      cursor: pointer;
    }

    /* Graphs Layout */
    .svg-wrap {
      width: 100%;
      position: relative;
    }

    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }

    /* SVG Elements */
    .axis { stroke: #94a3b8; stroke-width: 1.5; stroke-linecap: round; }
    .grid { stroke: #f1f5f9; stroke-dasharray: 4,4; stroke-width: 1; }
    .eq-line { stroke: #f59e0b; stroke-width: 1.5; stroke-dasharray: 4,3; }
    
    .label-title { font-size: 13px; font-weight: 700; fill: #1e2945; text-anchor: middle; }
    .label-axis { font-size: 11px; font-weight: 600; fill: #64748b; }
    .label-curve { font-size: 11px; font-weight: 700; }
    .label-eq { font-size: 11px; font-weight: 700; fill: #d97706; text-anchor: middle; }

    /* Key distinction callout */
    .summary-bar {
      display: flex;
      justify-content: space-around;
      gap: 8px;
      font-size: 12px;
      font-weight: 600;
      padding: 6px 10px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 6px;
    }

    .summary-item {
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .badge-equal {
      color: #0284c7;
      background: #e0f2fe;
      padding: 2px 6px;
      border-radius: 4px;
    }

    .badge-const {
      color: #7c3aed;
      background: #ede9fe;
      padding: 2px 6px;
      border-radius: 4px;
    }
  </style>
</head>
<body>

<div class="container">
  
  <div class="controls">
    <div class="btn-group">
      <button id="btnPlay" onclick="togglePlay()">▶ Play</button>
      <button id="btn0" onclick="goToStep(0)">Start</button>
      <button id="btn1" onclick="goToStep(50)">Approaching</button>
      <button id="btn2" class="active" onclick="goToStep(100)">Equilibrium</button>
    </div>
    <div class="slider-container">
      <span class="slider-label">Time:</span>
      <input type="range" id="timeSlider" min="0" max="100" value="100" oninput="onSlider(this.value)">
    </div>
  </div>

  
  <div class="svg-wrap">
    <svg viewBox="0 0 660 270">
      <defs>
        
        <clipPath id="clipLeft">
          <rect id="clipRectL" x="50" y="0" width="240" height="260" />
        </clipPath>
        <clipPath id="clipRight">
          <rect id="clipRectR" x="380" y="0" width="240" height="260" />
        </clipPath>
        
        
        <marker id="arrow" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1.5 L 8 5 L 0 8.5 z" fill="#94a3b8" />
        </marker>
      </defs>

      
      <g>
        
        <text x="170" y="24" class="label-title">Reaction Rate vs. Time</text>

        
        <line x1="50" y1="210" x2="300" y2="210" class="axis" marker-end="url(#arrow)" />
        <line x1="50" y1="210" x2="50" y2="40" class="axis" marker-end="url(#arrow)" />

        <text x="300" y="225" class="label-axis" text-anchor="end">Time →</text>
        <text x="45" y="42" class="label-axis" text-anchor="end">Rate</text>

        
        <line x1="175" y1="45" x2="175" y2="210" class="eq-line" id="eqLineL" opacity="1" />
        <text x="175" y="40" class="label-eq">Equilibrium</text>

        
        <g clip-path="url(#clipLeft)">
          
          <path d="M 50,65 C 100,125 140,140 175,140 L 290,140" fill="none" stroke="#22b7ff" stroke-width="3" stroke-linecap="round" />
          
          <path d="M 50,205 C 100,155 140,140 175,140 L 290,140" fill="none" stroke="#8b5cf6" stroke-width="3" stroke-linecap="round" />
        </g>

        
        <circle id="dotRf" cx="290" cy="140" r="4.5" fill="#22b7ff" stroke="#ffffff" stroke-width="1.5" />
        <circle id="dotRr" cx="290" cy="140" r="4.5" fill="#8b5cf6" stroke="#ffffff" stroke-width="1.5" />

        
        <text x="56" y="80" class="label-curve" fill="#22b7ff">Forward Rate</text>
        <text x="56" y="195" class="label-curve" fill="#8b5cf6">Reverse Rate</text>
        <text x="235" y="132" class="label-curve" fill="#0284c7" text-anchor="middle">Rates Equal</text>
        <text x="235" y="156" class="label-curve" fill="#64748b" text-anchor="middle" font-size="10">(Forward = Reverse)</text>
      </g>

      
      <g>
        
        <text x="500" y="24" class="label-title">Concentration vs. Time</text>

        
        <line x1="380" y1="210" x2="630" y2="210" class="axis" marker-end="url(#arrow)" />
        <line x1="380" y1="210" x2="380" y2="40" class="axis" marker-end="url(#arrow)" />

        <text x="630" y="225" class="label-axis" text-anchor="end">Time →</text>
        <text x="375" y="42" class="label-axis" text-anchor="end">Amount [ ]</text>

        
        <line x1="505" y1="45" x2="505" y2="210" class="eq-line" id="eqLineR" opacity="1" />
        <text x="505" y="40" class="label-eq">Equilibrium</text>

        
        <g clip-path="url(#clipRight)">
          
          <path d="M 380,65 C 430,105 475,115 505,115 L 620,115" fill="none" stroke="#22b7ff" stroke-width="3" stroke-linecap="round" />
          
          <path d="M 380,205 C 430,175 475,165 505,165 L 620,165" fill="none" stroke="#8b5cf6" stroke-width="3" stroke-linecap="round" />
        </g>

        
        <circle id="dotReact" cx="620" cy="115" r="4.5" fill="#22b7ff" stroke="#ffffff" stroke-width="1.5" />
        <circle id="dotProd" cx="620" cy="165" r="4.5" fill="#8b5cf6" stroke="#ffffff" stroke-width="1.5" />

        
        <text x="386" y="80" class="label-curve" fill="#22b7ff">[ Reactants ]</text>
        <text x="386" y="195" class="label-curve" fill="#8b5cf6">[ Products ]</text>
        <text x="565" y="108" class="label-curve" fill="#0284c7" text-anchor="middle">Constant [ ]</text>
        <text x="565" y="158" class="label-curve" fill="#7c3aed" text-anchor="middle">Constant [ ]</text>
        <text x="565" y="192" class="label-curve" fill="#64748b" text-anchor="middle" font-size="10">(Amounts stay steady)</text>
      </g>
    </svg>
  </div>

  
  <div class="summary-bar">
    <div class="summary-item">
      <span>Rates:</span>
      <span class="badge-equal">Must be EQUAL</span>
    </div>
    <div class="summary-item">
      <span>Concentrations:</span>
      <span class="badge-const">Must be CONSTANT (not necessarily equal)</span>
    </div>
  </div>
</div>

<script>
  let isPlaying = false;
  let animTimer = null;
  const slider = document.getElementById('timeSlider');
  const btnPlay = document.getElementById('btnPlay');
  
  // Left curve helpers
  function getRateY(tNorm, isForward) {
    if (tNorm >= 0.52) return 140; // Flat after equilibrium
    const p = tNorm / 0.52;
    if (isForward) {
      return 65 + (140 - 65) * (1 - Math.pow(1 - p, 2));
    } else {
      return 205 - (205 - 140) * (1 - Math.pow(1 - p, 2));
    }
  }

  // Right curve helpers
  function getConcY(tNorm, isReactant) {
    if (tNorm >= 0.52) return isReactant ? 115 : 165;
    const p = tNorm / 0.52;
    if (isReactant) {
      return 65 + (115 - 65) * (1 - Math.pow(1 - p, 2));
    } else {
      return 205 - (205 - 165) * (1 - Math.pow(1 - p, 2));
    }
  }

  function updateVisual(val) {
    const t = parseFloat(val) / 100; // 0 to 1
    
    // Width of reveal
    const wLeft = t * 240;
    const wRight = t * 240;
    document.getElementById('clipRectL').setAttribute('width', Math.max(1, wLeft));
    document.getElementById('clipRectR').setAttribute('width', Math.max(1, wRight));

    // Dots positioning
    const curXL = 50 + t * 240;
    const curXR = 380 + t * 240;

    const dotRf = document.getElementById('dotRf');
    const dotRr = document.getElementById('dotRr');
    const dotReact = document.getElementById('dotReact');
    const dotProd = document.getElementById('dotProd');

    dotRf.setAttribute('cx', curXL);
    dotRf.setAttribute('cy', getRateY(t, true));
    
    dotRr.setAttribute('cx', curXL);
    dotRr.setAttribute('cy', getRateY(t, false));

    dotReact.setAttribute('cx', curXR);
    dotReact.setAttribute('cy', getConcY(t, true));

    dotProd.setAttribute('cx', curXR);
    dotProd.setAttribute('cy', getConcY(t, false));

    // Update active button styles
    document.querySelectorAll('.btn-group button:not(#btnPlay)').forEach(b => b.classList.remove('active'));
    if (val == 0) document.getElementById('btn0').classList.add('active');
    else if (val == 50) document.getElementById('btn1').classList.add('active');
    else if (val == 100) document.getElementById('btn2').classList.add('active');
  }

  function onSlider(val) {
    if (isPlaying) pause();
    updateVisual(val);
  }

  function goToStep(val) {
    if (isPlaying) pause();
    slider.value = val;
    updateVisual(val);
  }

  function togglePlay() {
    if (isPlaying) {
      pause();
    } else {
      play();
    }
  }

  function play() {
    if (parseFloat(slider.value) >= 100) {
      slider.value = 0;
    }
    isPlaying = true;
    btnPlay.textContent = '⏸ Pause';
    btnPlay.classList.add('active');
    
    animTimer = setInterval(() => {
      let v = parseFloat(slider.value) + 1.2;
      if (v >= 100) {
        v = 100;
        slider.value = v;
        updateVisual(v);
        pause();
      } else {
        slider.value = v;
        updateVisual(v);
      }
    }, 30);
  }

  function pause() {
    isPlaying = false;
    btnPlay.textContent = '▶ Play';
    btnPlay.classList.remove('active');
    if (animTimer) clearInterval(animTimer);
  }

  // Initial render
  updateVisual(100);
</script>

</body>
</html>

OGS.11.PS.EQ.3

Aligned learning resources

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