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    <div class="title">Separation of Fundamental Forces</div>
    <div class="subtitle">Cosmic evolution from unified superforce to the four fundamental interactions</div>
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The Big Bang Theory and the Early Universe Timeline

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<body>

  
  <div class="header">
    <div class="title">Big Bang Nucleosynthesis</div>
    <div class="subtitle">t ≈ 10s – 20 min | T drops below 10⁹ K</div>
  </div>

  
  <div class="nav-container">
    <button class="step-tab active" data-step="0">1. Deuterium</button>
    <button class="step-tab" data-step="1">2. Intermediates</button>
    <button class="step-tab" data-step="2">3. Helium-4</button>
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        <div class="symbol-plus">+</div>
        <div class="reaction-item">
          <div class="cluster"><div class="nucleon neutron">0</div></div>
          <div class="item-label">Neutron</div>
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        <div class="symbol-arrow">→</div>
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            <div class="nucleon proton">+</div>
            <div class="nucleon neutron">0</div>
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          <div class="cluster"><div class="photon"><span class="photon-label">γ</span></div></div>
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      <div class="stage-note">Deuterium Bottleneck: High-energy photons split ²H until cooling allowed stability.</div>
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          <div class="item-label">n⁰</div>
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        <div class="symbol-arrow">→</div>
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            <div class="nucleon proton">+</div>
            <div class="nucleon neutron">0</div>
            <div class="nucleon neutron">0</div>
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          <div class="item-label">³H (Tritium) + γ</div>
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      <div class="stage-note">Deuterons rapidly fuse into mass-3 nuclei (³He and ³H).</div>
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        <div class="reaction-item">
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            <div class="nucleon proton">+</div>
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            <div class="nucleon neutron">0</div>
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          <div class="cluster"><div class="nucleon neutron">0</div></div>
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        <div class="yield-bar-wrapper">
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            <div class="yield-h">~75% ¹H</div>
            <div class="yield-he">~25% ⁴He</div>
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            <div class="yield-val">~75%</div>
            <div class="yield-name">¹H Protons</div>
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          <div class="yield-card">
            <div class="yield-val">~24.8%</div>
            <div class="yield-name">⁴He Helium</div>
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          <div class="yield-card">
            <div class="yield-val">~0.01%</div>
            <div class="yield-name">²H Deuterium</div>
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      </div>
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      <div class="legend-item"><div class="legend-swatch swatch-p"></div> Proton (p⁺)</div>
      <div class="legend-item"><div class="legend-swatch swatch-n"></div> Neutron (n⁰)</div>
      <div class="legend-item"><div class="legend-swatch swatch-g"></div> Gamma (γ)</div>
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      border: none;
      color: #8b949e;
      padding: 5px 12px;
      font-size: 12px;
      font-weight: 600;
      border-radius: 6px;
      cursor: pointer;
      transition: background 0.2s, color 0.2s;
    }

    .toggle-btn.active {
      background: #238636;
      color: #ffffff;
    }

    .slider-box {
      display: flex;
      align-items: center;
      gap: 6px;
      font-size: 12px;
      color: #8b949e;
      background: #161b22;
      border: 1px solid #30363d;
      border-radius: 8px;
      padding: 4px 10px;
    }

    input[type="range"] {
      accent-color: #2ea043;
      cursor: pointer;
      width: 90px;
    }

    .canvas-container {
      position: relative;
      width: 100%;
      max-width: 520px;
      aspect-ratio: 16 / 10;
      border-radius: 10px;
      overflow: hidden;
      border: 1px solid #30363d;
      background: #030712;
    }

    canvas {
      display: block;
      width: 100%;
      height: 100%;
    }

    .bottom-bar {
      display: flex;
      justify-content: space-between;
      align-items: center;
      width: 100%;
      max-width: 520px;
      gap: 8px;
      flex-wrap: wrap;
    }

    .status-badge {
      font-size: 12px;
      font-weight: 600;
      padding: 4px 10px;
      border-radius: 6px;
      background: #161b22;
      border: 1px solid #30363d;
      color: #f0883e;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .status-badge.clear {
      color: #58a6ff;
    }

    .legend {
      display: flex;
      gap: 8px;
      font-size: 11px;
      color: #c9d1d9;
    }

    .legend-item {
      display: inline-flex;
      align-items: center;
      gap: 4px;
      background: #161b22;
      border: 1px solid #30363d;
      border-radius: 4px;
      padding: 2px 6px;
    }

    .swatch {
      display: inline-block;
      width: 9px;
      height: 9px;
      border-radius: 50%;
    }
    .swatch.proton { background: #ff4444; }
    .swatch.electron { background: #38bdf8; }
    .swatch.photon {
      background: #facc15;
      width: 12px;
      height: 3px;
      border-radius: 2px;
    }
  </style>
</head>
<body>

  <div class="controls-row">
    <div class="btn-group">
      <button id="btnBefore" class="toggle-btn active">Before (Opaque)</button>
      <button id="btnAfter" class="toggle-btn">After (Transparent)</button>
    </div>
    <div class="slider-box">
      <span>Recombination:</span>
      <input id="recSlider" type="range" min="0" max="100" value="0">
    </div>
  </div>

  <div class="canvas-container">
    <canvas id="simCanvas"></canvas>
  </div>

  <div class="bottom-bar">
    <div id="statusBadge" class="status-badge">
      <span>● Opaque Plasma (Photons Trapped)</span>
    </div>
    <div class="legend">
      <span class="legend-item"><span class="swatch proton"></span>p⁺ Proton</span>
      <span class="legend-item"><span class="swatch electron"></span>e⁻ Electron</span>
      <span class="legend-item"><span class="swatch photon"></span>γ Photon</span>
    </div>
  </div>

  <script>
    const canvas = document.getElementById('simCanvas');
    const ctx = canvas.getContext('2d');
    const btnBefore = document.getElementById('btnBefore');
    const btnAfter = document.getElementById('btnAfter');
    const slider = document.getElementById('recSlider');
    const statusBadge = document.getElementById('statusBadge');

    let recombination = 0; // 0 to 1
    let targetRecombination = 0;

    const NUM_ATOMS = 6;
    const NUM_PHOTONS = 9;

    // Fixed proton base sites
    const protons = [
      { x: 0.20, y: 0.30 },
      { x: 0.50, y: 0.25 },
      { x: 0.80, y: 0.35 },
      { x: 0.25, y: 0.75 },
      { x: 0.55, y: 0.70 },
      { x: 0.82, y: 0.75 }
    ];

    // Electron state
    const electrons = protons.map((p, i) => ({
      freeX: p.x + (Math.random() - 0.5) * 0.2,
      freeY: p.y + (Math.random() - 0.5) * 0.2,
      vx: (Math.random() - 0.5) * 0.003,
      vy: (Math.random() - 0.5) * 0.003,
      orbitAngle: Math.random() * Math.PI * 2,
      orbitSpeed: 0.04 + Math.random() * 0.02,
      targetIndex: i
    }));

    // Photon packets
    const photons = [];
    for (let i = 0; i < NUM_PHOTONS; i++) {
      photons.push({
        x: Math.random(),
        y: 0.12 + (i / NUM_PHOTONS) * 0.76,
        baseY: 0.12 + (i / NUM_PHOTONS) * 0.76,
        vx: 0.005 + Math.random() * 0.002,
        vy: 0,
        scatterTimer: Math.random() * 60,
        scatterAngle: Math.random() * Math.PI * 2,
        phase: Math.random() * Math.PI * 2
      });
    }

    function resizeCanvas() {
      const rect = canvas.getBoundingClientRect();
      const dpr = window.devicePixelRatio || 1;
      canvas.width = rect.width * dpr;
      canvas.height = rect.height * dpr;
      ctx.scale(dpr, dpr);
    }
    window.addEventListener('resize', resizeCanvas);
    resizeCanvas();

    function setRecombination(val, updateSlider = true) {
      targetRecombination = Math.max(0, Math.min(1, val));
      if (updateSlider) slider.value = Math.round(targetRecombination * 100);
      btnBefore.classList.toggle('active', targetRecombination < 0.5);
      btnAfter.classList.toggle('active', targetRecombination >= 0.5);
    }

    btnBefore.onclick = () => setRecombination(0);
    btnAfter.onclick = () => setRecombination(1);
    slider.oninput = (e) => setRecombination(parseFloat(e.target.value) / 100, false);

    function updateBadge() {
      if (recombination < 0.4) {
        statusBadge.className = 'status-badge';
        statusBadge.innerHTML = '<span>● Opaque Plasma (Photons Trapped)</span>';
      } else if (recombination > 0.6) {
        statusBadge.className = 'status-badge clear';
        statusBadge.innerHTML = '<span>✦ Transparent Space (Free Streaming CMB)</span>';
      } else {
        statusBadge.className = 'status-badge';
        statusBadge.innerHTML = '<span>◌ Recombination in Progress...</span>';
      }
    }

    let time = 0;

    function render() {
      // Smooth interpolation toward target
      recombination += (targetRecombination - recombination) * 0.08;
      updateBadge();

      const w = canvas.getBoundingClientRect().width;
      const h = canvas.getBoundingClientRect().height;

      ctx.clearRect(0, 0, w, h);

      // 1. Warm plasma glow background (opacity decreases with recombination)
      const plasmaOpacity = (1 - recombination) * 0.28;
      if (plasmaOpacity > 0.005) {
        const bgGrad = ctx.createRadialGradient(w * 0.5, h * 0.5, 10, w * 0.5, h * 0.5, w * 0.7);
        bgGrad.addColorStop(0, `rgba(255, 110, 40, ${plasmaOpacity})`);
        bgGrad.addColorStop(1, `rgba(255, 60, 20, 0)`);
        ctx.fillStyle = bgGrad;
        ctx.fillRect(0, 0, w, h);
      }

      time += 1;

      // 2. Draw Neutral Atoms / Bound Orbits (fade in with recombination)
      const orbitRadius = Math.min(w, h) * 0.09;

      protons.forEach((p, i) => {
        const px = p.x * w;
        const py = p.y * h;

        // Draw dashed orbital shell when recombined
        if (recombination > 0.05) {
          ctx.save();
          ctx.beginPath();
          ctx.arc(px, py, orbitRadius, 0, Math.PI * 2);
          ctx.strokeStyle = `rgba(56, 189, 248, ${0.45 * recombination})`;
          ctx.lineWidth = 1.2;
          ctx.setLineDash([4, 4]);
          ctx.stroke();

          // Labeled atom tag
          if (recombination > 0.75) {
            ctx.fillStyle = `rgba(200, 225, 255, ${(recombination - 0.75) * 4 * 0.6})`;
            ctx.font = '10px sans-serif';
            ctx.textAlign = 'center';
            ctx.fillText('¹H', px, py - orbitRadius - 4);
          }
          ctx.restore();
        }

        // Draw Proton (p+)
        ctx.beginPath();
        ctx.arc(px, py, 7, 0, Math.PI * 2);
        ctx.fillStyle = '#ef4444';
        ctx.shadowColor = '#ff4444';
        ctx.shadowBlur = 8;
        ctx.fill();
        ctx.shadowBlur = 0;

        // "+" symbol on proton
        ctx.fillStyle = '#ffffff';
        ctx.font = 'bold 9px sans-serif';
        ctx.textAlign = 'center';
        ctx.textBaseline = 'middle';
        ctx.fillText('+', px, py);
      });

      // 3. Update and Draw Electrons (e-)
      electrons.forEach((e) => {
        const proton = protons[e.targetIndex];
        const pX = proton.x * w;
        const pY = proton.y * h;

        // Free motion
        e.freeX += e.vx;
        e.freeY += e.vy;
        if (e.freeX < 0.05 || e.freeX > 0.95) e.vx *= -1;
        if (e.freeY < 0.05 || e.freeY > 0.95) e.vy *= -1;

        // Bound orbit position
        e.orbitAngle += e.orbitSpeed;
        const boundX = pX + Math.cos(e.orbitAngle) * orbitRadius;
        const boundY = pY + Math.sin(e.orbitAngle) * orbitRadius;

        // Interpolate between free motion & bound orbit
        const curX = (e.freeX * w) * (1 - recombination) + boundX * recombination;
        const curY = (e.freeY * h) * (1 - recombination) + boundY * recombination;

        // Draw electron
        ctx.beginPath();
        ctx.arc(curX, curY, 4, 0, Math.PI * 2);
        ctx.fillStyle = '#38bdf8';
        ctx.shadowColor = '#38bdf8';
        ctx.shadowBlur = 6;
        ctx.fill();
        ctx.shadowBlur = 0;

        // "-" symbol
        ctx.fillStyle = '#0f172a';
        ctx.font = 'bold 8px sans-serif';
        ctx.textAlign = 'center';
        ctx.textBaseline = 'middle';
        ctx.fillText('−', curX, curY - 0.5);
      });

      // 4. Update and Draw Photons (γ waves)
      photons.forEach((pt) => {
        pt.phase += 0.2;

        // Free streaming path (straight line left-to-right)
        const straightSpeed = 0.007;

        if (recombination < 0.5) {
          // Scattering behavior (zig-zag / bouncing off free electrons)
          pt.scatterTimer -= 1;
          if (pt.scatterTimer <= 0) {
            pt.scatterTimer = 20 + Math.random() * 35;
            pt.scatterAngle = Math.random() * Math.PI * 2;
          }
          const scatterSpeed = 0.004 * (1 - recombination);
          pt.x += Math.cos(pt.scatterAngle) * scatterSpeed + straightSpeed * recombination;
          pt.y += Math.sin(pt.scatterAngle) * scatterSpeed;

          // Wrap boundaries
          if (pt.x > 1.05) pt.x = -0.05;
          if (pt.x < -0.05) pt.x = 1.05;
          if (pt.y > 0.95) pt.y = 0.05;
          if (pt.y < 0.05) pt.y = 0.95;
        } else {
          // Decoupled free streaming
          pt.x += straightSpeed;
          pt.y += (pt.baseY - pt.y) * 0.05; // Return to clean horizontal tracks
          if (pt.x > 1.08) {
            pt.x = -0.08;
            pt.y = pt.baseY;
          }
        }

        const cx = pt.x * w;
        const cy = pt.y * h;

        // Draw photon sinusoidal wave packet
        ctx.save();
        ctx.beginPath();
        const waveLength = 22;
        const waveAmp = 3.5;
        const numPoints = 12;

        for (let j = 0; j <= numPoints; j++) {
          const t = (j / numPoints) * waveLength - waveLength / 2;
          const waveX = cx + t;
          const waveY = cy + Math.sin(pt.phase + j * 0.6) * waveAmp;
          if (j === 0) ctx.moveTo(waveX, waveY);
          else ctx.lineTo(waveX, waveY);
        }

        ctx.strokeStyle = '#facc15';
        ctx.lineWidth = 2;
        ctx.shadowColor = '#facc15';
        ctx.shadowBlur = 7;
        ctx.stroke();
        ctx.restore();
      });

      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="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, sans-serif;
      background: #0b1021;
      color: #cad5e2;
      display: flex;
      flex-direction: column;
      height: 100%;
      min-height: 440px;
      padding: 12px;
      justify-content: space-between;
      user-select: none;
    }

    /* Epoch Header & Slider */
    .timeline-ctrl {
      display: flex;
      flex-direction: column;
      gap: 6px;
      width: 100%;
    }
    .slider-container {
      position: relative;
      width: 100%;
      display: flex;
      align-items: center;
    }
    input[type="range"] {
      width: 100%;
      -webkit-appearance: none;
      appearance: none;
      height: 6px;
      border-radius: 3px;
      background: #1e2945;
      outline: none;
      cursor: pointer;
    }
    input[type="range"]::-webkit-slider-thumb {
      -webkit-appearance: none;
      appearance: none;
      width: 20px;
      height: 20px;
      border-radius: 50%;
      background: #ff9f43;
      box-shadow: 0 0 10px #ff9f43;
      border: 2px solid #ffffff;
      cursor: pointer;
    }
    input[type="range"]::-moz-range-thumb {
      width: 20px;
      height: 20px;
      border-radius: 50%;
      background: #ff9f43;
      box-shadow: 0 0 10px #ff9f43;
      border: 2px solid #ffffff;
      cursor: pointer;
    }
    .milestones {
      display: flex;
      justify-content: space-between;
      font-size: 11px;
      color: #6b7280;
      font-weight: 600;
    }
    .milestones span {
      cursor: pointer;
      transition: color 0.2s;
    }
    .milestones span.active {
      color: #ff9f43;
    }

    /* Central Visual Canvas */
    .visual-stage {
      position: relative;
      flex: 1;
      min-height: 190px;
      max-height: 250px;
      margin: 8px 0;
      border-radius: 12px;
      background: radial-gradient(circle at center, #151d38 0%, #080c1a 100%);
      overflow: hidden;
      display: flex;
      align-items: center;
      justify-content: center;
      border: 1px solid rgba(255, 255, 255, 0.08);
    }
    canvas {
      width: 100%;
      height: 100%;
      display: block;
    }

    /* Dynamic Stat Cards */
    .stats-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 8px;
    }
    @media (min-width: 520px) {
      .stats-grid {
        grid-template-columns: repeat(4, 1fr);
      }
    }
    .stat-card {
      background: #11182c;
      border: 1px solid rgba(255, 255, 255, 0.08);
      border-radius: 8px;
      padding: 8px 10px;
      display: flex;
      flex-direction: column;
      justify-content: center;
    }
    .stat-label {
      font-size: 10px;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #6b7280;
      font-weight: 700;
      margin-bottom: 2px;
    }
    .stat-val {
      font-size: 13px;
      font-weight: 600;
      color: #ffffff;
      white-space: nowrap;
      overflow: hidden;
      text-overflow: ellipsis;
    }
    .stat-val.highlight {
      color: #ff9f43;
    }
  </style>
</head>
<body>

  <div class="timeline-ctrl">
    <div class="slider-container">
      <input type="range" id="timeSlider" min="0" max="4" step="1" value="0">
    </div>
    <div class="milestones" id="milestones">
      <span data-step="0" class="active">10⁻⁴³ s</span>
      <span data-step="1">10⁻³² s</span>
      <span data-step="2">10⁻⁶ s</span>
      <span data-step="3">3 min</span>
      <span data-step="4">380k yr</span>
    </div>
  </div>

  <div class="visual-stage">
    <canvas id="viewCanvas"></canvas>
  </div>

  <div class="stats-grid">
    <div class="stat-card">
      <div class="stat-label">Time</div>
      <div class="stat-val" id="timeVal">10⁻⁴³ s</div>
    </div>
    <div class="stat-card">
      <div class="stat-label">Temperature</div>
      <div class="stat-val highlight" id="tempVal">10³² K · 10¹⁹ GeV</div>
    </div>
    <div class="stat-card">
      <div class="stat-label">Epoch</div>
      <div class="stat-val" id="epochVal">Planck Epoch</div>
    </div>
    <div class="stat-card">
      <div class="stat-label">State</div>
      <div class="stat-val" id="stateVal">Quantum Singularity</div>
    </div>
  </div>

  <script>
    const epochs = [
      {
        time: "10⁻⁴³ s",
        temp: "10³² K · 10¹⁹ GeV",
        name: "Planck Epoch",
        state: "Quantum Singularity"
      },
      {
        time: "10⁻³² s",
        temp: "10²⁷ K · 10¹⁴ GeV",
        name: "Cosmic Inflation",
        state: "Exponential Expansion"
      },
      {
        time: "10⁻⁶ s",
        temp: "10¹² K · 1 GeV",
        name: "Quark Epoch",
        state: "Quark-Gluon Soup"
      },
      {
        time: "3 min",
        temp: "10⁹ K · 0.1 MeV",
        name: "Nucleosynthesis",
        state: "Opaque Plasma (Trapped Light)"
      },
      {
        time: "380,000 yr",
        temp: "3,000 K · 0.3 eV",
        name: "Recombination",
        state: "Transparent Space (CMB Released)"
      }
    ];

    const slider = document.getElementById('timeSlider');
    const milestoneSpans = document.querySelectorAll('#milestones span');
    const timeVal = document.getElementById('timeVal');
    const tempVal = document.getElementById('tempVal');
    const epochVal = document.getElementById('epochVal');
    const stateVal = document.getElementById('stateVal');
    const canvas = document.getElementById('viewCanvas');
    const ctx = canvas.getContext('2d');

    let currentStep = 0;
    let animTime = 0;

    function resize() {
      canvas.width = canvas.parentElement.clientWidth * window.devicePixelRatio;
      canvas.height = canvas.parentElement.clientHeight * window.devicePixelRatio;
    }
    window.addEventListener('resize', resize);
    resize();

    function updateEpoch(idx) {
      currentStep = parseInt(idx);
      slider.value = currentStep;
      milestoneSpans.forEach((span, i) => {
        span.classList.toggle('active', i === currentStep);
      });
      const data = epochs[currentStep];
      timeVal.textContent = data.time;
      tempVal.textContent = data.temp;
      epochVal.textContent = data.name;
      stateVal.textContent = data.state;
    }

    slider.addEventListener('input', (e) => updateEpoch(e.target.value));
    milestoneSpans.forEach(span => {
      span.addEventListener('click', () => updateEpoch(span.dataset.step));
    });

    // Particle system for visual rendering
    const particles = Array.from({ length: 65 }, () => ({
      x: Math.random(),
      y: Math.random(),
      vx: (Math.random() - 0.5) * 0.004,
      vy: (Math.random() - 0.5) * 0.004,
      type: Math.floor(Math.random() * 3), // 0: proton/quark, 1: electron, 2: photon
      phase: Math.random() * Math.PI * 2
    }));

    function draw() {
      animTime += 0.03;
      const w = canvas.width;
      const h = canvas.height;
      const cx = w / 2;
      const cy = h / 2;

      ctx.clearRect(0, 0, w, h);

      if (currentStep === 0) {
        // Quantum Foam Singularity
        const pulse = Math.sin(animTime * 6) * 4 + 12;
        const grad = ctx.createRadialGradient(cx, cy, 0, cx, cy, pulse * 5);
        grad.addColorStop(0, '#ffffff');
        grad.addColorStop(0.2, '#ff9f43');
        grad.addColorStop(0.6, 'rgba(238, 82, 83, 0.4)');
        grad.addColorStop(1, 'transparent');

        ctx.fillStyle = grad;
        ctx.beginPath();
        ctx.arc(cx, cy, pulse * 5, 0, Math.PI * 2);
        ctx.fill();

        ctx.fillStyle = '#ffffff';
        ctx.beginPath();
        ctx.arc(cx, cy, pulse * 0.8, 0, Math.PI * 2);
        ctx.fill();

      } else if (currentStep === 1) {
        // Inflation: Rapid expansion wavefronts
        const maxR = Math.min(w, h) * 0.46;
        for (let i = 0; i < 4; i++) {
          const r = ((animTime * 40 + i * (maxR / 4)) % maxR);
          const alpha = 1 - (r / maxR);
          ctx.strokeStyle = `rgba(255, 159, 67, ${alpha * 0.8})`;
          ctx.lineWidth = 3;
          ctx.beginPath();
          ctx.arc(cx, cy, r, 0, Math.PI * 2);
          ctx.stroke();
        }
        ctx.fillStyle = '#ffffff';
        ctx.beginPath();
        ctx.arc(cx, cy, 6, 0, Math.PI * 2);
        ctx.fill();

      } else if (currentStep === 2) {
        // Quark-Gluon Soup: Chaotic hot dense colored particles
        const rBound = Math.min(w, h) * 0.38;
        ctx.fillStyle = 'rgba(238, 82, 83, 0.12)';
        ctx.beginPath();
        ctx.arc(cx, cy, rBound, 0, Math.PI * 2);
        ctx.fill();

        particles.forEach((p) => {
          const px = cx + (p.x - 0.5) * rBound * 1.8;
          const py = cy + (p.y - 0.5) * rBound * 1.8;
          const color = p.type === 0 ? '#ff9f43' : (p.type === 1 ? '#ee5253' : '#22b7ff');
          ctx.fillStyle = color;
          ctx.shadowColor = color;
          ctx.shadowBlur = 6;
          ctx.beginPath();
          ctx.arc(px + Math.sin(animTime * 3 + p.phase) * 5, py + Math.cos(animTime * 3 + p.phase) * 5, 3.5, 0, Math.PI * 2);
          ctx.fill();
        });
        ctx.shadowBlur = 0;

      } else if (currentStep === 3) {
        // Nucleosynthesis / Opaque Plasma: Photons scattering/trapped
        const rBound = Math.min(w, h) * 0.42;
        ctx.fillStyle = 'rgba(255, 159, 67, 0.15)';
        ctx.beginPath();
        ctx.arc(cx, cy, rBound, 0, Math.PI * 2);
        ctx.fill();

        // Photons trapped (bouncing lines)
        ctx.strokeStyle = '#ffffff';
        ctx.lineWidth = 1.5;
        for (let i = 0; i < 6; i++) {
          const t = animTime * 2 + i;
          const x1 = cx + Math.cos(t) * (rBound * 0.5);
          const y1 = cy + Math.sin(t * 1.3) * (rBound * 0.5);
          const x2 = x1 + Math.cos(t * 3) * 20;
          const y2 = y1 + Math.sin(t * 3) * 20;
          ctx.beginPath();
          ctx.moveTo(x1, y1);
          ctx.lineTo(x2, y2);
          ctx.stroke();
        }

        // Nuclei (Protons + Neutrons bound)
        for (let i = 0; i < 8; i++) {
          const ang = (i / 8) * Math.PI * 2 + animTime * 0.2;
          const nx = cx + Math.cos(ang) * (rBound * 0.6);
          const ny = cy + Math.sin(ang) * (rBound * 0.6);
          ctx.fillStyle = '#ee5253';
          ctx.beginPath();
          ctx.arc(nx - 3, ny, 4, 0, Math.PI * 2);
          ctx.fill();
          ctx.fillStyle = '#cad5e2';
          ctx.beginPath();
          ctx.arc(nx + 3, ny, 4, 0, Math.PI * 2);
          ctx.fill();
        }

      } else if (currentStep === 4) {
        // Recombination: Neutral atoms formed, photons streaming freely in straight rays
        const rBound = Math.min(w, h) * 0.44;

        // Neutral Atoms (Proton + orbiting electron)
        for (let i = 0; i < 6; i++) {
          const ang = (i / 6) * Math.PI * 2;
          const ax = cx + Math.cos(ang) * (rBound * 0.45);
          const ay = cy + Math.sin(ang) * (rBound * 0.45);

          // Nucleus
          ctx.fillStyle = '#ee5253';
          ctx.beginPath();
          ctx.arc(ax, ay, 4, 0, Math.PI * 2);
          ctx.fill();

          // Orbit orbit path
          ctx.strokeStyle = 'rgba(255, 255, 255, 0.15)';
          ctx.lineWidth = 1;
          ctx.beginPath();
          ctx.arc(ax, ay, 12, 0, Math.PI * 2);
          ctx.stroke();

          // Orbiting Electron
          const eAng = animTime * 3 + i;
          ctx.fillStyle = '#22b7ff';
          ctx.beginPath();
          ctx.arc(ax + Math.cos(eAng) * 12, ay + Math.sin(eAng) * 12, 2.5, 0, Math.PI * 2);
          ctx.fill();
        }

        // Free streaming CMB Photons (Warm glowing waves streaming outward)
        for (let i = 0; i < 12; i++) {
          const rayAng = (i / 12) * Math.PI * 2;
          const dist = ((animTime * 60 + i * 30) % (rBound * 1.1));
          const rx = cx + Math.cos(rayAng) * dist;
          const ry = cy + Math.sin(rayAng) * dist;

          ctx.fillStyle = '#ff9f43';
          ctx.shadowColor = '#ff9f43';
          ctx.shadowBlur = 8;
          ctx.beginPath();
          ctx.arc(rx, ry, 3, 0, Math.PI * 2);
          ctx.fill();
        }
        ctx.shadowBlur = 0;
      }

      requestAnimationFrame(draw);
    }

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

OGS.11.ESS.5

Aligned learning resources

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