<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }

    body {
      width: 100%;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      background: transparent;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 8px 12px 10px;
    }

    .diagram-wrap {
      width: 100%;
      max-width: 460px;
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
    }

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

    /* Motion animation */
    .rotating #bone-group {
      animation: circumduct 3.6s ease-in-out infinite;
      transform-origin: 230px 130px;
    }

    .rotating #orbit-path {
      opacity: 1;
      stroke-dashoffset: 0;
      animation: dash 1.8s linear infinite;
    }

    @keyframes circumduct {
      0% {
        transform: rotate(0deg) skewX(0deg);
      }
      25% {
        transform: rotate(16deg) skewX(5deg);
      }
      50% {
        transform: rotate(0deg) skewX(0deg);
      }
      75% {
        transform: rotate(-16deg) skewX(-5deg);
      }
      100% {
        transform: rotate(0deg) skewX(0deg);
      }
    }

    @keyframes dash {
      to {
        stroke-dashoffset: -24;
      }
    }

    .btn-wrap {
      margin-top: 4px;
      display: flex;
      justify-content: center;
    }

    .btn-action {
      background: #22b7ff;
      color: #ffffff;
      border: none;
      font-size: 13.5px;
      font-weight: 600;
      padding: 7px 18px;
      border-radius: 20px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      box-shadow: 0 2px 8px rgba(34, 183, 255, 0.35);
      transition: background 0.2s, box-shadow 0.2s;
    }

    .btn-action:hover {
      background: #0ea5e9;
      box-shadow: 0 4px 12px rgba(34, 183, 255, 0.45);
    }

    .btn-action:active {
      background: #0284c7;
    }

    .label-title {
      font-size: 13px;
      font-weight: 700;
      fill: #1e2945;
    }

    .label-sub {
      font-size: 11px;
      font-weight: 500;
      fill: #64748b;
    }
  </style>
</head>
<body>
  <div class="diagram-wrap" id="jointApp">
    <svg viewBox="0 0 460 268" aria-label="Ball and socket joint diagram">
      <defs>
        
        <radialGradient id="ballGrad" cx="36%" cy="32%" r="68%">
          <stop offset="0%" stop-color="#ffffff" />
          <stop offset="35%" stop-color="#bae6fd" />
          <stop offset="75%" stop-color="#38bdf8" />
          <stop offset="100%" stop-color="#0284c7" />
        </radialGradient>

        <linearGradient id="boneGrad" x1="0%" y1="0%" x2="100%" y2="0%">
          <stop offset="0%" stop-color="#e2e8f0" />
          <stop offset="50%" stop-color="#ffffff" />
          <stop offset="100%" stop-color="#cbd5e1" />
        </linearGradient>

        <linearGradient id="socketGrad" x1="0%" y1="0%" x2="0%" y2="100%">
          <stop offset="0%" stop-color="#94a3b8" />
          <stop offset="50%" stop-color="#cbd5e1" />
          <stop offset="100%" stop-color="#f1f5f9" />
        </linearGradient>

        <filter id="softShadow" x="-20%" y="-20%" width="140%" height="140%">
          <feDropShadow dx="0" dy="3" stdDeviation="3.5" flood-color="#0f172a" flood-opacity="0.12" />
        </filter>

        
        <marker id="arrowHead" 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="#22b7ff" />
        </marker>
      </defs>

      
      <ellipse cx="230" cy="225" rx="72" ry="16" fill="#e0f2fe" opacity="0.6" />
      <path id="orbit-path" d="M 158 225 A 72 16 0 1 0 302 225 A 72 16 0 1 0 158 225" fill="none" stroke="#22b7ff" stroke-width="2.2" stroke-dasharray="6 5" marker-end="url(#arrowHead)" opacity="0.85" />
      
      
      <text x="230" y="256" text-anchor="middle" class="label-title" fill="#22b7ff" font-size="11.5">360° Multi-Directional Motion</text>

      
      <g id="bone-group">
        
        <path d="M 221 148 L 219 225 C 219 231 241 231 241 225 L 239 148 Z" fill="url(#boneGrad)" stroke="#94a3b8" stroke-width="1.5" />
        
        <circle cx="230" cy="130" r="36" fill="url(#ballGrad)" filter="url(#softShadow)" stroke="#0284c7" stroke-width="1.5" />
      </g>

      
      <g id="socket-group">
        
        <path d="M 172 84 C 172 54 288 54 288 84 C 288 103 282 116 272 128 C 263 102 248 93 230 93 C 212 93 197 102 188 128 C 178 116 172 103 172 84 Z" fill="url(#socketGrad)" stroke="#64748b" stroke-width="1.8" />
        
        
        <path d="M 184 125 C 190 98 208 94 230 94 C 252 94 270 98 276 125 C 282 153 263 172 230 172 C 197 172 178 153 184 125 Z" fill="none" stroke="#22b7ff" stroke-width="2" stroke-dasharray="4 3" opacity="0.75" />
        
        
        <path d="M 180 119 C 175 144 192 166 230 166 C 268 166 285 144 280 119" fill="none" stroke="#64748b" stroke-width="2.5" stroke-linecap="round" />
      </g>

      
      <g>
        <path d="M 152 64 L 186 64 L 206 82" fill="none" stroke="#1e2945" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round" />
        <circle cx="206" cy="82" r="3" fill="#1e2945" />
        <text x="14" y="58" text-anchor="start" class="label-title">Socket</text>
        <text x="14" y="74" text-anchor="start" class="label-sub">(pelvis / shoulder blade)</text>
      </g>

      
      <g>
        <path d="M 308 130 L 268 130" fill="none" stroke="#1e2945" stroke-width="1.5" stroke-linecap="round" />
        <circle cx="266" cy="130" r="3" fill="#1e2945" />
        <text x="446" y="124" text-anchor="end" class="label-title">Ball</text>
        <text x="446" y="140" text-anchor="end" class="label-sub">(head of femur / humerus)</text>
      </g>
    </svg>

    <div class="btn-wrap">
      <button class="btn-action" id="toggleBtn" aria-label="Toggle joint rotation">
        <span id="btnIcon">⏸</span>
        <span id="btnText">Pause</span>
      </button>
    </div>
  </div>

  <script>
    const app = document.getElementById('jointApp');
    const btn = document.getElementById('toggleBtn');
    const btnIcon = document.getElementById('btnIcon');
    const btnText = document.getElementById('btnText');

    let isRotating = true;
    app.classList.add('rotating');

    function toggleRotation() {
      isRotating = !isRotating;
      if (isRotating) {
        app.classList.add('rotating');
        btnIcon.textContent = '⏸';
        btnText.textContent = 'Pause';
      } else {
        app.classList.remove('rotating');
        btnIcon.textContent = '▶';
        btnText.textContent = 'Rotate Joint';
      }
    }

    btn.addEventListener('click', toggleRotation);
  </script>
</body>
</html>

Types of Joints: Hinge, Ball-and-Socket, and Fixed

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }

    body {
      width: 100%;
      min-height: 100vh;
      background: #f8f9fa;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 8px 12px 14px;
      user-select: none;
      overflow-x: hidden;
    }

    .main-stage {
      width: 100%;
      max-width: 540px;
      aspect-ratio: 4 / 3;
      position: relative;
      margin-bottom: 6px;
    }

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

    /* Bone styling - increased contrast on outlines */
    .bone-plate {
      fill: #ffffff;
      stroke: #475569;
      stroke-width: 2;
      stroke-linejoin: round;
    }

    .bone-highlight {
      fill: #f1f5f9;
    }

    .bone-feature {
      fill: #e2e8f0;
      stroke: #475569;
      stroke-width: 1.5;
    }

    .suture-line {
      fill: none;
      stroke: #f59e0b;
      stroke-width: 3;
      stroke-linecap: round;
      stroke-linejoin: round;
    }

    .suture-pulse {
      animation: pulseGlow 2.5s infinite ease-in-out;
    }

    @keyframes pulseGlow {
      0%, 100% { stroke: #f59e0b; stroke-width: 3; }
      50% { stroke: #d97706; stroke-width: 4; }
    }

    /* Callout styling */
    .callout-ring {
      fill: #ffffff;
      stroke: #3b82f6;
      stroke-width: 2.5;
      filter: drop-shadow(0 4px 10px rgba(30, 41, 69, 0.12));
    }

    .callout-line {
      stroke: #64748b;
      stroke-width: 1.5;
      stroke-dasharray: 4 3;
    }

    /* Bone interlocking puzzle shapes */
    .puzzle-left {
      fill: #e2e8f0;
      stroke: #475569;
      stroke-width: 1.8;
      transition: transform 0.6s ease;
    }

    .puzzle-right {
      fill: #cbd5e1;
      stroke: #475569;
      stroke-width: 1.8;
      transition: transform 0.6s ease;
    }

    .interlock-suture {
      fill: none;
      stroke: #f59e0b;
      stroke-width: 3.5;
      stroke-linecap: round;
      stroke-linejoin: round;
    }

    /* Labels and Badges */
    .svg-text {
      font-size: 13px;
      font-weight: 700;
      fill: #1e2945;
      text-anchor: middle;
      font-family: inherit;
    }

    .callout-header-bg {
      fill: #e0f2fe;
      stroke: #38bdf8;
      stroke-width: 1;
      rx: 5;
    }

    .callout-header-text {
      font-size: 10px;
      font-weight: 800;
      letter-spacing: 0.5px;
      fill: #0369a1;
      text-anchor: middle;
    }

    .badge-rect {
      fill: #fee2e2;
      stroke: #ef4444;
      stroke-width: 1.5;
      rx: 6;
    }

    .badge-text {
      font-size: 11px;
      font-weight: 800;
      fill: #b91c1c;
      text-anchor: middle;
    }

    /* Interactive controls */
    .controls {
      display: flex;
      gap: 10px;
      z-index: 10;
      justify-content: center;
      width: 100%;
      max-width: 540px;
    }

    .btn {
      padding: 7px 16px;
      font-size: 12.5px;
      font-weight: 600;
      border-radius: 8px;
      border: 1.5px solid #cbd5e1;
      background: #ffffff;
      color: #1e2945;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 6px;
      transition: background 0.2s, border-color 0.2s, color 0.2s, opacity 0.2s;
    }

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

    .btn.active {
      background: #1e2945;
      color: #ffffff;
      border-color: #1e2945;
    }

    /* Smooth, non-strobing rigidity animations */
    .testing .arrow-left {
      animation: pullL 1.4s infinite ease-in-out alternate;
    }
    .testing .arrow-right {
      animation: pullR 1.4s infinite ease-in-out alternate;
    }
    .testing .callout-group {
      animation: gentleStress 1.4s infinite ease-in-out;
    }

    @keyframes pullL {
      0% { transform: translateX(0); opacity: 0.5; }
      100% { transform: translateX(-6px); opacity: 1; }
    }
    @keyframes pullR {
      0% { transform: translateX(0); opacity: 0.5; }
      100% { transform: translateX(6px); opacity: 1; }
    }
    @keyframes gentleStress {
      0%, 100% { transform: translate(415px, 175px) rotate(0deg); }
      50% { transform: translate(415px, 175px) rotate(0.4deg); }
    }

    .force-arrow {
      opacity: 0;
      transition: opacity 0.4s ease;
    }
    .testing .force-arrow {
      opacity: 1;
    }

    @media (max-width: 480px) {
      .svg-text {
        font-size: 12px;
      }
      .btn {
        padding: 6px 12px;
        font-size: 11.5px;
      }
    }
  </style>
</head>
<body>

  <div class="main-stage" id="stage">
    <svg viewBox="0 0 540 400">
      
      <line class="callout-line" x1="195" y1="135" x2="335" y2="105" />
      <line class="callout-line" x1="195" y1="135" x2="335" y2="245" />

      
      <g id="skull-group">
        
        <path class="bone-plate bone-highlight" d="M 125 185 C 95 190 75 230 95 270 C 115 310 155 315 190 295 C 185 270 175 250 170 230 Z" />

        
        <path class="bone-plate" d="M 170 230 C 175 250 185 270 190 295 C 220 280 230 250 225 215 C 195 210 180 215 170 230 Z" />

        
        <path class="bone-plate" d="M 125 185 C 105 150 130 95 185 85 C 215 105 235 135 240 170 C 210 175 180 180 125 185 Z" />

        
        <path class="bone-plate bone-highlight" d="M 185 85 C 240 80 280 115 285 175 C 275 190 260 195 245 200 C 240 170 215 105 185 85 Z" />

        
        <path class="bone-plate" d="M 285 175 C 295 200 285 230 280 245 C 265 245 250 240 245 250 C 240 275 250 300 235 305 C 210 310 195 295 190 295 C 220 280 230 250 225 215 C 240 210 260 210 270 195 C 275 185 280 180 285 175 Z" />

        
        <ellipse class="bone-feature" cx="265" cy="195" rx="14" ry="18" />
        <path class="bone-feature" d="M 278 220 L 270 240 L 280 240 Z" />

        
        
        <path id="suture-target" class="suture-line suture-pulse" d="M 185 85 Q 192 100 188 115 Q 200 125 195 135 Q 208 145 202 155 Q 220 162 240 170" />

        
        <path class="suture-line" d="M 125 185 Q 135 170 145 180 Q 155 168 170 178 Q 185 170 215 173 Q 230 170 240 170" />

        
        <path class="suture-line" d="M 170 230 Q 185 210 205 215 Q 220 210 225 215" />

        
        <text class="svg-text" x="195" y="55">Fixed Joints (Sutures)</text>
        <path d="M 195 62 L 195 76" stroke="#f59e0b" stroke-width="1.8" stroke-linecap="round" />
        <circle cx="195" cy="76" r="3" fill="#f59e0b" />
      </g>

      
      <g class="callout-group" transform="translate(415, 175)">
        
        <g transform="translate(0, -96)">
          <rect class="callout-header-bg" x="-74" y="-11" width="148" height="22" />
          <text class="callout-header-text" x="0" y="4">INTERLOCKING EDGES</text>
        </g>

        
        <circle class="callout-ring" cx="0" cy="0" r="80" />

        
        <clipPath id="calloutClip">
          <circle cx="0" cy="0" r="78" />
        </clipPath>

        <g clip-path="url(#calloutClip)">
          
          <path class="puzzle-left" d="
            M -90 -90
            L -8 -90
            L -8 -60
            L 12 -45
            L -10 -30
            L 14 -10
            L -12 10
            L 15 35
            L -10 55
            L 10 75
            L -8 90
            L -90 90
            Z
          " />

          
          <path class="puzzle-right" d="
            M 90 -90
            L -6 -90
            L -6 -60
            L 14 -45
            L -8 -30
            L 16 -10
            L -10 10
            L 17 35
            L -8 55
            L 12 75
            L -6 90
            L 90 90
            Z
          " />

          
          <path class="interlock-suture" d="
            M -7 -88
            L -7 -60
            L 13 -45
            L -9 -30
            L 15 -10
            L -11 10
            L 16 35
            L -9 55
            L 11 75
            L -7 88
          " />

          
          <g class="force-arrow arrow-left">
            <path d="M -25 0 L -54 0 M -45 -7 L -55 0 L -45 7" stroke="#ef4444" stroke-width="3" stroke-linecap="round" stroke-linejoin="round" />
            <text x="-40" y="-12" fill="#ef4444" font-size="10" font-weight="700" text-anchor="middle">Tension</text>
          </g>
          <g class="force-arrow arrow-right">
            <path d="M 25 0 L 54 0 M 45 -7 L 55 0 L 45 7" stroke="#ef4444" stroke-width="3" stroke-linecap="round" stroke-linejoin="round" />
            <text x="40" y="-12" fill="#ef4444" font-size="10" font-weight="700" text-anchor="middle">Tension</text>
          </g>
        </g>

        
        <g transform="translate(0, 56)">
          <rect class="badge-rect" x="-68" y="-12" width="136" height="24" />
          <text class="badge-text" x="0" y="4">🔒 No Movement Allowed</text>
        </g>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <button class="btn active" id="btn-view">✦ Structure</button>
    <button class="btn" id="btn-test">⚡ Test Joint Rigidity</button>
  </div>

  <script>
    const stage = document.getElementById('stage');
    const btnView = document.getElementById('btn-view');
    const btnTest = document.getElementById('btn-test');

    function setMode(testing) {
      if (testing) {
        stage.classList.add('testing');
        btnTest.classList.add('active');
        btnView.classList.remove('active');
      } else {
        stage.classList.remove('testing');
        btnView.classList.add('active');
        btnTest.classList.remove('active');
      }
    }

    btnView.addEventListener('click', () => setMode(false));
    btnTest.addEventListener('click', () => setMode(true));
  </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;
      background: #f8fafc;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      justify-content: center;
      min-height: 100%;
    }

    .grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 10px;
      width: 100%;
      max-width: 640px;
      margin: 0 auto;
    }

    @media (max-width: 480px) {
      .grid {
        grid-template-columns: 1fr;
        gap: 8px;
      }
    }

    .joint-card {
      background: #ffffff;
      border-radius: 14px;
      border: 2px solid #e2e8f0;
      padding: 12px 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      transition: box-shadow 0.2s ease, border-color 0.2s ease;
      cursor: pointer;
      user-select: none;
    }

    .joint-card:hover, .joint-card.active {
      box-shadow: 0 6px 16px rgba(0, 0, 0, 0.07);
    }

    .card-hinge.active { border-color: #3b82f6; }
    .card-ball.active { border-color: #8b5cf6; }
    .card-fixed.active { border-color: #059669; }

    .badge {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      padding: 3px 8px;
      border-radius: 999px;
      margin-bottom: 6px;
    }

    .badge-hinge { background: #eff6ff; color: #2563eb; }
    .badge-ball { background: #f5f3ff; color: #7c3aed; }
    .badge-fixed { background: #ecfdf5; color: #059669; }

    .title {
      font-size: 15px;
      font-weight: 700;
      line-height: 1.2;
      margin-bottom: 2px;
    }

    .examples {
      font-size: 12px;
      color: #64748b;
      font-weight: 500;
      margin-bottom: 8px;
    }

    .stage {
      width: 90px;
      height: 90px;
      position: relative;
      display: flex;
      align-items: center;
      justify-content: center;
      margin: 4px 0 8px 0;
    }

    /* Hinge Animation */
    .hinge-base {
      position: absolute;
      width: 10px;
      height: 48px;
      background: #94a3b8;
      border-radius: 4px;
      left: 24px;
      top: 21px;
    }
    .hinge-pin {
      position: absolute;
      width: 14px;
      height: 14px;
      background: #2563eb;
      border-radius: 50%;
      left: 22px;
      top: 38px;
      z-index: 2;
    }
    .hinge-arm {
      position: absolute;
      width: 44px;
      height: 10px;
      background: #3b82f6;
      border-radius: 5px;
      left: 29px;
      top: 40px;
      transform-origin: 0% 50%;
      animation: swing 3s ease-in-out infinite;
    }
    @keyframes swing {
      0%, 100% { transform: rotate(0deg); }
      50% { transform: rotate(-75deg); }
    }

    /* Ball & Socket Animation */
    .socket {
      position: absolute;
      width: 44px;
      height: 44px;
      border: 5px solid #cbd5e1;
      border-right-color: transparent;
      border-radius: 50%;
      transform: rotate(45deg);
    }
    .ball-stem {
      position: absolute;
      width: 42px;
      height: 42px;
      animation: orbit 3.6s linear infinite;
    }
    .ball {
      position: absolute;
      width: 22px;
      height: 22px;
      background: #8b5cf6;
      border-radius: 50%;
      left: 10px;
      top: 10px;
      box-shadow: inset -2px -2px 5px rgba(0,0,0,0.2);
    }
    .stem {
      position: absolute;
      width: 32px;
      height: 8px;
      background: #a78bfa;
      border-radius: 4px;
      left: 26px;
      top: 17px;
    }
    @keyframes orbit {
      0% { transform: rotate(0deg) scale(0.95); }
      25% { transform: rotate(15deg) scale(1.05); }
      50% { transform: rotate(0deg) scale(0.95); }
      75% { transform: rotate(-25deg) scale(1.02); }
      100% { transform: rotate(0deg) scale(0.95); }
    }

    /* Fixed Joint Visual */
    .puzzle-box {
      width: 60px;
      height: 60px;
      position: relative;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .fixed-svg {
      width: 60px;
      height: 60px;
    }
    .lock-badge {
      position: absolute;
      width: 20px;
      height: 20px;
      background: #059669;
      color: white;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 11px;
      box-shadow: 0 2px 4px rgba(0,0,0,0.15);
    }

    .motion-tag {
      font-size: 12px;
      font-weight: 700;
      color: #334155;
      background: #f1f5f9;
      padding: 4px 10px;
      border-radius: 6px;
      display: inline-flex;
      align-items: center;
      gap: 4px;
    }

    @media (max-width: 480px) {
      .joint-card {
        flex-direction: row;
        text-align: left;
        padding: 8px 12px;
        justify-content: space-between;
      }
      .card-info {
        display: flex;
        flex-direction: column;
        align-items: flex-start;
      }
      .stage {
        width: 64px;
        height: 64px;
        margin: 0;
      }
      .hinge-base { left: 16px; top: 14px; height: 36px; }
      .hinge-pin { left: 14px; top: 27px; }
      .hinge-arm { left: 20px; top: 29px; width: 34px; }
      .puzzle-box, .fixed-svg { width: 48px; height: 48px; }
      .socket { width: 34px; height: 34px; }
      .ball-stem { width: 34px; height: 34px; }
      .ball { width: 18px; height: 18px; left: 8px; top: 8px; }
      .stem { width: 24px; left: 20px; top: 13px; }
    }
  </style>
</head>
<body>

  <div class="grid">
    
    <div class="joint-card card-hinge active" onclick="activate(this)">
      <div class="card-info">
        <span class="badge badge-hinge">1 Direction</span>
        <div class="title">Hinge</div>
        <div class="examples">Knee & Elbow</div>
      </div>
      <div class="stage">
        <div class="hinge-base"></div>
        <div class="hinge-pin"></div>
        <div class="hinge-arm"></div>
      </div>
      <div class="motion-tag">↔ Back & Forth</div>
    </div>

    
    <div class="joint-card card-ball" onclick="activate(this)">
      <div class="card-info">
        <span class="badge badge-ball">360° Rotation</span>
        <div class="title">Ball & Socket</div>
        <div class="examples">Shoulder & Hip</div>
      </div>
      <div class="stage">
        <div class="socket"></div>
        <div class="ball-stem">
          <div class="ball"></div>
          <div class="stem"></div>
        </div>
      </div>
      <div class="motion-tag">🔄 All Directions</div>
    </div>

    
    <div class="joint-card card-fixed" onclick="activate(this)">
      <div class="card-info">
        <span class="badge badge-fixed">0° Motion</span>
        <div class="title">Fixed Joint</div>
        <div class="examples">Skull Sutures</div>
      </div>
      <div class="stage">
        <div class="puzzle-box">
          <svg class="fixed-svg" viewBox="0 0 60 60">
            <rect x="6" y="6" width="48" height="48" rx="8" fill="#e2e8f0"/>
            <path d="M 6 30 Q 18 24 24 30 T 36 30 T 54 30" fill="none" stroke="#059669" stroke-width="3" stroke-dasharray="3 2" stroke-linecap="round"/>
            <path d="M 30 6 Q 24 18 30 24 T 30 36 T 30 54" fill="none" stroke="#059669" stroke-width="3" stroke-dasharray="3 2" stroke-linecap="round"/>
          </svg>
          <div class="lock-badge">🔒</div>
        </div>
      </div>
      <div class="motion-tag">⛔ No Movement</div>
    </div>
  </div>

  <script>
    function activate(el) {
      document.querySelectorAll('.joint-card').forEach(c => c.classList.remove('active'));
      el.classList.add('active');
    }
  </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;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
    }

    .header {
      text-align: center;
      margin-bottom: 8px;
    }
    .title {
      font-size: 18px;
      font-weight: 700;
      color: #1e2945;
    }
    .badge {
      display: inline-block;
      margin-top: 4px;
      padding: 3px 10px;
      font-size: 12px;
      font-weight: 600;
      color: #0077b6;
      background: #e0f2fe;
      border-radius: 12px;
    }

    .comparison {
      display: flex;
      gap: 12px;
      width: 100%;
      max-width: 580px;
      justify-content: center;
    }

    .panel {
      flex: 1;
      min-width: 0;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 8px 6px 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      cursor: pointer;
      user-select: none;
      transition: border-color 0.2s, box-shadow 0.2s;
    }
    .panel:hover {
      border-color: #22b7ff;
      box-shadow: 0 2px 8px rgba(34, 183, 255, 0.15);
    }

    .panel-label {
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
      margin-bottom: 4px;
    }

    svg {
      width: 100%;
      height: 190px;
      overflow: visible;
    }

    /* Animated elements */
    .door-leaf {
      transform-origin: 55px 145px;
      transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    }
    .forearm {
      transform-origin: 75px 85px;
      transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    }
    .motion-arc {
      transition: opacity 0.3s;
    }

    /* Bent state */
    .bent .door-leaf {
      transform: rotate(-72deg);
    }
    .bent .forearm {
      transform: rotate(-95deg);
    }

    .controls {
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 6px;
      margin-top: 8px;
    }

    .btn-toggle {
      background: #22b7ff;
      color: #ffffff;
      border: none;
      padding: 9px 20px;
      font-size: 14px;
      font-weight: 600;
      border-radius: 20px;
      cursor: pointer;
      box-shadow: 0 2px 6px rgba(34, 183, 255, 0.35);
      transition: background 0.2s, transform 0.1s;
    }
    .btn-toggle:active {
      transform: scale(0.97);
    }

    .status-text {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
    }
  </style>
</head>
<body>

  <div class="header">
    <div class="title">Hinge Joint</div>
    <div class="badge">Moves in 1 direction</div>
  </div>

  <div class="comparison" id="diagramArea">
    
    <div class="panel" id="doorPanel" title="Click to toggle">
      <div class="panel-label">Door Hinge</div>
      <svg viewBox="0 0 180 190">
        
        <rect x="25" y="140" width="30" height="24" rx="3" fill="#cbd5e1" stroke="#94a3b8" stroke-width="2"/>
        <line x1="20" y1="164" x2="60" y2="164" stroke="#94a3b8" stroke-width="2"/>

        
        <path d="M 130,145 A 75 75 0 0 0 78,73" fill="none" stroke="#22b7ff" stroke-width="2.5" stroke-dasharray="4,3"/>
        <polygon points="73,73 83,68 83,78" fill="#22b7ff"/>

        
        <g class="door-leaf" id="doorLeaf">
          <rect x="55" y="139" width="85" height="12" rx="3" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <circle cx="125" cy="145" r="3" fill="#0284c7"/>
        </g>

        
        <circle cx="55" cy="145" r="7" fill="#f59e0b" stroke="#b45309" stroke-width="2"/>
        <circle cx="55" cy="145" r="2.5" fill="#ffffff"/>
        <text x="55" y="178" font-size="11" font-weight="700" fill="#b45309" text-anchor="middle">Hinge</text>
      </svg>
    </div>

    
    <div class="panel" id="armPanel" title="Click to toggle">
      <div class="panel-label">Elbow Joint</div>
      <svg viewBox="0 0 180 190">
        
        <g>
          
          <ellipse cx="75" cy="22" rx="14" ry="7" fill="#e2e8f0" stroke="#64748b" stroke-width="2"/>
          
          <path d="M 67,24 L 69,76 Q 69,82 64,84 L 86,84 Q 81,82 81,76 L 83,24 Z" fill="#f1f5f9" stroke="#64748b" stroke-width="2"/>
        </g>

        
        <path d="M 75,155 A 70 70 0 0 1 10,95" fill="none" stroke="#22b7ff" stroke-width="2.5" stroke-dasharray="4,3"/>
        <polygon points="10,95 16,104 22,96" fill="#22b7ff"/>

        
        <g class="forearm" id="forearmBone">
          
          <path d="M 68,88 L 70,148 Q 66,155 75,158 Q 84,155 80,148 L 82,88 Z" fill="#f1f5f9" stroke="#64748b" stroke-width="2"/>
          
          <path d="M 70,158 Q 67,175 75,178 Q 83,175 80,158 Z" fill="#fee2e2" stroke="#f87171" stroke-width="1.5"/>
        </g>

        
        <circle cx="75" cy="85" r="7" fill="#f59e0b" stroke="#b45309" stroke-width="2"/>
        <circle cx="75" cy="85" r="2.5" fill="#ffffff"/>
        <text x="115" y="89" font-size="11" font-weight="700" fill="#b45309" text-anchor="start">Joint</text>
      </svg>
    </div>
  </div>

  <div class="controls">
    <button class="btn-toggle" id="toggleBtn">Bend / Straighten</button>
    <div class="status-text" id="statusText">State: Straightened (Open)</div>
  </div>

  <script>
    const diagramArea = document.getElementById('diagramArea');
    const toggleBtn = document.getElementById('toggleBtn');
    const statusText = document.getElementById('statusText');

    let isBent = false;

    function toggleJoint() {
      isBent = !isBent;
      if (isBent) {
        diagramArea.classList.add('bent');
        statusText.textContent = 'State: Bent (Closed / Flexed)';
      } else {
        diagramArea.classList.remove('bent');
        statusText.textContent = 'State: Straightened (Open / Extended)';
      }
    }

    toggleBtn.addEventListener('click', toggleJoint);
    document.getElementById('doorPanel').addEventListener('click', toggleJoint);
    document.getElementById('armPanel').addEventListener('click', toggleJoint);
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      width: 100%;
      min-height: 100vh;
      background: #f8fafc;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      overflow-x: hidden;
      color: #1e2945;
      padding: 8px;
    }
    .diagram-wrap {
      width: 100%;
      max-width: 600px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 8px;
    }
    svg {
      width: 100%;
      height: auto;
      max-height: 440px;
      display: block;
      user-select: none;
    }
    .controls {
      display: flex;
      flex-wrap: wrap;
      justify-content: center;
      align-items: center;
      gap: 10px;
      width: 100%;
      padding: 4px 0;
    }
    .btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      padding: 7px 16px;
      font-size: 13px;
      font-weight: 600;
      color: #334155;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.08);
      transition: background 0.2s, border-color 0.2s, box-shadow 0.2s, color 0.2s;
    }
    .btn:hover {
      background: #f1f5f9;
      border-color: #94a3b8;
    }
    .btn.active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.35);
    }
    .label-box {
      font-size: 12px;
      font-weight: 700;
      fill: #1e293b;
    }

    @media (max-width: 420px) {
      .btn {
        padding: 6px 12px;
        font-size: 12px;
      }
    }
  </style>
</head>
<body>

<div class="diagram-wrap">
  <svg viewBox="0 0 600 430" preserveAspectRatio="xMidYMid meet">
    <defs>
      
      <linearGradient id="boneGrad" x1="0%" y1="0%" x2="100%" y2="100%">
        <stop offset="0%" stop-color="#fef3c7" />
        <stop offset="50%" stop-color="#fde68a" />
        <stop offset="100%" stop-color="#f59e0b" stop-opacity="0.6" />
      </linearGradient>

      
      <pattern id="bonePatt" width="10" height="10" patternUnits="userSpaceOnUse">
        <circle cx="2" cy="2" r="1" fill="#d97706" opacity="0.25" />
        <circle cx="7" cy="7" r="1.2" fill="#b45309" opacity="0.25" />
      </pattern>

      
      <radialGradient id="ballGrad" cx="35%" cy="35%" r="65%">
        <stop offset="0%" stop-color="#fb923c" />
        <stop offset="70%" stop-color="#ea580c" />
        <stop offset="100%" stop-color="#9a3412" />
      </radialGradient>

      
      <radialGradient id="scleraGrad" cx="40%" cy="40%" r="60%">
        <stop offset="0%" stop-color="#ffffff" />
        <stop offset="85%" stop-color="#f1f5f9" />
        <stop offset="100%" stop-color="#cbd5e1" />
      </radialGradient>

      <linearGradient id="irisGrad" x1="0%" y1="0%" x2="100%" y2="100%">
        <stop offset="0%" stop-color="#38bdf8" />
        <stop offset="100%" stop-color="#0284c7" />
      </linearGradient>

      
      <filter id="softGlow" x="-20%" y="-20%" width="140%" height="140%">
        <feDropShadow dx="0" dy="2" stdDeviation="3" flood-opacity="0.15" />
      </filter>
      
      <filter id="shieldGlow" x="-20%" y="-20%" width="140%" height="140%">
        <feDropShadow dx="0" dy="0" stdDeviation="4" flood-color="#10b981" flood-opacity="0.6" />
      </filter>
    </defs>

    
    <path d="M 330,40 Q 480,40 500,180 Q 520,320 400,410 L 330,410 C 370,360 380,290 380,225 C 380,160 360,90 330,40 Z" 
          fill="#f1f5f9" stroke="#cbd5e1" stroke-width="2" />
    
    <text x="440" y="225" font-size="12" font-weight="700" fill="#475569" text-anchor="middle">Cranial Cavity</text>

    
    <path d="M 230,175 C 280,185 360,200 360,235 C 360,270 280,285 230,295 C 275,280 340,265 340,235 C 340,205 275,190 230,175 Z" 
          fill="#cbd5e1" opacity="0.35" />

    
    <path d="M 320,235 C 345,235 375,238 395,242" stroke="#f43f5e" stroke-width="8" stroke-linecap="round" fill="none" opacity="0.8" />
    <path d="M 320,235 C 345,235 375,238 395,242" stroke="#ffe4e6" stroke-width="3" stroke-linecap="round" fill="none" />

    
    <g id="eyeballGroup" transform="translate(0, 0)">
      
      <ellipse cx="295" cy="235" rx="34" ry="34" fill="url(#scleraGrad)" stroke="#94a3b8" stroke-width="1.5" filter="url(#softGlow)" />
      
      
      <path d="M 268,214 C 254,222 254,248 268,256" fill="none" stroke="#38bdf8" stroke-width="2.5" opacity="0.8" />
      <path d="M 268,214 C 255,222 255,248 268,256 C 265,246 265,224 268,214 Z" fill="#e0f2fe" opacity="0.4" />

      
      <ellipse cx="272" cy="235" rx="7" ry="17" fill="url(#irisGrad)" />
      <ellipse cx="269" cy="235" rx="3.5" ry="9" fill="#0f172a" />
      <circle cx="267" cy="231" r="2" fill="#ffffff" />
    </g>

    
    
    <path d="M 210,50 
             Q 220,110 215,160 
             Q 212,175 228,178 
             C 275,188 360,205 360,235 
             C 360,265 275,282 228,292 
             Q 212,295 215,310 
             Q 220,360 210,420 
             L 330,420 
             C 360,370 375,305 375,235 
             C 375,165 360,100 330,50 Z" 
          fill="url(#boneGrad)" stroke="#b45309" stroke-width="3" stroke-linejoin="round" />

    
    <path d="M 210,50 
             Q 220,110 215,160 
             Q 212,175 228,178 
             C 275,188 360,205 360,235 
             C 360,265 275,282 228,292 
             Q 212,295 215,310 
             Q 220,360 210,420 
             L 330,420 
             C 360,370 375,305 375,235 
             C 375,165 360,100 330,50 Z" 
          fill="url(#bonePatt)" opacity="0.9" />

    
    <path d="M 206,45 Q 216,110 212,160 Q 210,172 216,176" fill="none" stroke="#fbcfe8" stroke-width="3" opacity="0.6" />
    <path d="M 216,294 Q 210,298 212,310 Q 216,360 206,425" fill="none" stroke="#fbcfe8" stroke-width="3" opacity="0.6" />

    
    <g id="protectiveBridge" opacity="0.95">
      <line x1="214" y1="168" x2="214" y2="302" stroke="#10b981" stroke-width="3.5" stroke-dasharray="6,4" filter="url(#shieldGlow)" />
      
      
      <circle cx="214" cy="168" r="5" fill="#10b981" />
      <circle cx="214" cy="302" r="5" fill="#10b981" />

      
      <line x1="214" y1="235" x2="255" y2="235" stroke="#10b981" stroke-width="2" stroke-linecap="round" />
      <path d="M 214,231 L 214,239 M 255,231 L 255,239" stroke="#10b981" stroke-width="2" />
    </g>

    
    <g id="ballEntity" transform="translate(0, 0)">
      
      <circle cx="95" cy="235" r="120" fill="url(#ballGrad)" stroke="#431407" stroke-width="2.5" />
      
      
      <ellipse cx="95" cy="235" rx="60" ry="120" fill="none" stroke="#431407" stroke-width="2.5" opacity="0.75" />
      <line x1="-25" y1="235" x2="215" y2="235" stroke="#431407" stroke-width="2.5" opacity="0.75" />
      <path d="M 35,130 Q 95,200 155,130" fill="none" stroke="#431407" stroke-width="2.5" opacity="0.75" />
      <path d="M 35,340 Q 95,270 155,340" fill="none" stroke="#431407" stroke-width="2.5" opacity="0.75" />

      
      <path id="impactRim" d="M 214,168 A 120 120 0 0 1 214,302" fill="none" stroke="#ffffff" stroke-width="3" opacity="0" stroke-linecap="round" />
    </g>

    

    
    <g>
      <line x1="215" y1="130" x2="160" y2="70" stroke="#b45309" stroke-width="1.5" />
      <circle cx="215" cy="130" r="3.5" fill="#b45309" />
      <rect x="45" y="48" width="140" height="30" rx="6" fill="#ffffff" stroke="#fde68a" stroke-width="1.5" filter="url(#softGlow)" />
      <text x="115" y="68" class="label-box" fill="#78350f" text-anchor="middle">Thick Bony Rim</text>
    </g>

    
    <g>
      <line x1="215" y1="335" x2="160" y2="380" stroke="#b45309" stroke-width="1.5" />
      <circle cx="215" cy="335" r="3.5" fill="#b45309" />
      <rect x="55" y="365" width="125" height="30" rx="6" fill="#ffffff" stroke="#fde68a" stroke-width="1.5" filter="url(#softGlow)" />
      <text x="117" y="385" class="label-box" fill="#78350f" text-anchor="middle">Cheekbone</text>
    </g>

    
    <g>
      <line x1="295" y1="201" x2="295" y2="120" stroke="#0284c7" stroke-width="1.5" />
      <circle cx="295" cy="201" r="3.5" fill="#0284c7" />
      <rect x="220" y="92" width="150" height="32" rx="6" fill="#ffffff" stroke="#bae6fd" stroke-width="1.5" filter="url(#softGlow)" />
      <text x="295" y="113" class="label-box" fill="#0369a1" text-anchor="middle">Recessed Eyeball</text>
    </g>

    
    <g>
      <line x1="355" y1="250" x2="420" y2="305" stroke="#475569" stroke-width="1.5" />
      <circle cx="355" cy="250" r="3.5" fill="#475569" />
      <rect x="375" y="300" width="125" height="30" rx="6" fill="#ffffff" stroke="#cbd5e1" stroke-width="1.5" filter="url(#softGlow)" />
      <text x="437" y="320" class="label-box" fill="#334155" text-anchor="middle">Bony Socket</text>
    </g>

    
    <g id="safetyBadge" transform="translate(235, 248)">
      <rect x="-4" y="-12" width="76" height="22" rx="11" fill="#ecfdf5" stroke="#10b981" stroke-width="1.2" />
      <text x="34" y="2" font-size="10" font-weight="700" fill="#047857" text-anchor="middle">SAFE GAP</text>
    </g>
  </svg>

  
  <div class="controls">
    <button id="stepBtn" class="btn" onclick="toggleImpact()">
      <span id="btnIcon">▶</span> <span id="btnText">Simulate Impact</span>
    </button>
    <button id="modeBtn" class="btn active" onclick="toggleAuto()">
      <span>🔄</span> <span>Auto Loop</span>
    </button>
  </div>
</div>

<script>
  const ball = document.getElementById('ballEntity');
  const impactRim = document.getElementById('impactRim');
  const safetyBadge = document.getElementById('safetyBadge');
  const btnIcon = document.getElementById('btnIcon');
  const btnText = document.getElementById('btnText');
  const modeBtn = document.getElementById('modeBtn');

  let isAuto = true;
  let isImpacted = false;
  let animTimer = null;
  let state = 0; // 0: approach, 1: contact/bounce

  function setImpactState(impact) {
    isImpacted = impact;
    if (impact) {
      // Ball touches the brow and cheekbone at x=0 offset
      ball.style.transform = 'translateX(0px)';
      ball.style.transition = 'transform 0.45s cubic-bezier(0.2, 0.8, 0.25, 1)';
      impactRim.style.opacity = '0.9';
      impactRim.style.transition = 'opacity 0.2s ease-in';
      safetyBadge.style.opacity = '1';
      safetyBadge.style.transform = 'translate(235px, 248px) scale(1.05)';
      safetyBadge.style.transition = 'transform 0.2s ease, opacity 0.2s ease';
      btnText.textContent = 'Reset Ball';
      btnIcon.textContent = '↺';
    } else {
      // Ball retracted back
      ball.style.transform = 'translateX(-70px)';
      ball.style.transition = 'transform 0.6s cubic-bezier(0.4, 0, 0.2, 1)';
      impactRim.style.opacity = '0';
      impactRim.style.transition = 'opacity 0.3s ease-out';
      safetyBadge.style.opacity = '0.7';
      safetyBadge.style.transform = 'translate(235px, 248px) scale(1)';
      safetyBadge.style.transition = 'transform 0.3s ease, opacity 0.3s ease';
      btnText.textContent = 'Simulate Impact';
      btnIcon.textContent = '▶';
    }
  }

  function toggleImpact() {
    if (isAuto) {
      stopAuto();
    }
    setImpactState(!isImpacted);
  }

  function loopStep() {
    if (!isAuto) return;
    state = (state + 1) % 2;
    setImpactState(state === 1);
    animTimer = setTimeout(loopStep, state === 1 ? 2200 : 1600);
  }

  function startAuto() {
    isAuto = true;
    modeBtn.classList.add('active');
    state = 0;
    setImpactState(false);
    clearTimeout(animTimer);
    animTimer = setTimeout(loopStep, 800);
  }

  function stopAuto() {
    isAuto = false;
    modeBtn.classList.remove('active');
    clearTimeout(animTimer);
  }

  function toggleAuto() {
    if (isAuto) {
      stopAuto();
    } else {
      startAuto();
    }
  }

  // Initialize
  startAuto();
</script>

</body>
</html>

The Skull: Protecting the Brain and Sensory Organs

<!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;
      background: #f8fafc;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      min-height: 100%;
      padding: 12px;
      user-select: none;
    }

    .toolbar {
      display: flex;
      gap: 8px;
      margin-bottom: 8px;
      width: 100%;
      max-width: 540px;
      justify-content: center;
    }

    .btn {
      flex: 1;
      padding: 8px 14px;
      font-size: 14px;
      font-weight: 600;
      border-radius: 8px;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #475569;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: background 0.2s, color 0.2s, box-shadow 0.2s;
    }

    .btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.3);
    }

    .diagram-svg {
      width: 100%;
      max-width: 540px;
      height: auto;
      display: block;
    }

    /* Sound wave animation */
    @keyframes soundTravel {
      0% { transform: translateX(0); opacity: 0; }
      20% { opacity: 0.9; }
      80% { opacity: 0.9; }
      100% { transform: translateX(115px); opacity: 0; }
    }

    .sound-pulse {
      animation: soundTravel 2.4s ease-in-out infinite;
      transform-origin: 0 0;
    }
    .wave-2 { animation-delay: 0.8s; }
    .wave-3 { animation-delay: 1.6s; }

    /* Ossicle vibration */
    @keyframes ossicleJiggle {
      0%, 100% { transform: rotate(0deg); }
      50% { transform: rotate(2deg); }
    }
    .ossicles {
      transform-origin: 365px 200px;
      animation: ossicleJiggle 0.6s ease-in-out infinite;
    }

    /* Impact tap animation */
    @keyframes tapImpact {
      0% { transform: scale(0.6); opacity: 0; }
      30% { transform: scale(1.1); opacity: 1; }
      70% { transform: scale(1); opacity: 0.9; }
      100% { transform: scale(1.2); opacity: 0; }
    }

    .knock-wave {
      animation: tapImpact 1.8s ease-out infinite;
      transform-origin: 310px 65px;
    }
    .knock-2 { animation-delay: 0.9s; }

    /* Mode switching */
    .mode-sound .impact-group { opacity: 0.15; transition: opacity 0.3s ease; }
    .mode-sound .sound-group { opacity: 1; transition: opacity 0.3s ease; }
    .mode-impact .sound-group { opacity: 0.2; transition: opacity 0.3s ease; }
    .mode-impact .impact-group { opacity: 1; transition: opacity 0.3s ease; }
  </style>
</head>
<body class="mode-sound">

  
  <div class="toolbar">
    <button class="btn active" id="btnSound" onclick="setMode('sound')">
      <span>🎵</span> Sound Path
    </button>
    <button class="btn" id="btnImpact" onclick="setMode('impact')">
      <span>🛡️</span> Bone Shield
    </button>
  </div>

  
  <svg class="diagram-svg" viewBox="0 0 540 370" fill="none" xmlns="http://www.w3.org/2000/svg">
    <defs>
      
      <pattern id="boneDots" width="16" height="16" patternUnits="userSpaceOnUse">
        <circle cx="4" cy="4" r="1.5" fill="#d8b4a0" opacity="0.45"/>
        <circle cx="12" cy="12" r="1.5" fill="#d8b4a0" opacity="0.45"/>
      </pattern>
      
      <linearGradient id="boneGrad" x1="180" y1="50" x2="480" y2="330" gradientUnits="userSpaceOnUse">
        <stop offset="0%" stop-color="#fdf2e9"/>
        <stop offset="100%" stop-color="#f5dccb"/>
      </linearGradient>
      <linearGradient id="shieldGrad" x1="0" y1="0" x2="0" y2="1">
        <stop offset="0%" stop-color="#38bdf8"/>
        <stop offset="100%" stop-color="#0284c7"/>
      </linearGradient>
    </defs>

    
    
    <path d="M 50,30 Q 180,10 320,15 Q 460,20 500,120 Q 520,200 500,320 L 160,320 L 140,240 Q 100,240 80,190 Q 60,140 135,140 L 150,140 Q 150,80 50,30 Z" fill="#fae8de" />

    
    <path d="M 180,35 Q 330,25 480,80 Q 495,180 480,310 L 195,310 Q 185,250 200,215 L 200,165 Q 180,110 180,35 Z" fill="url(#boneGrad)" stroke="#e2b99f" stroke-width="2"/>
    <path d="M 180,35 Q 330,25 480,80 Q 495,180 480,310 L 195,310 Q 185,250 200,215 L 200,165 Q 180,110 180,35 Z" fill="url(#boneDots)"/>

    
    
    <path d="M 115,180 Q 180,175 295,185 L 295,205 Q 180,195 115,200 Z" fill="#e0a990"/>
    
    <path d="M 290,165 C 330,145 420,145 445,185 C 465,225 435,265 375,265 C 315,265 285,230 290,165 Z" fill="#ffffff" stroke="#e2b99f" stroke-width="2"/>

    
    <path d="M 140,115 C 80,110 50,140 60,185 C 70,225 105,255 135,255 C 150,255 145,230 130,225 C 95,220 85,185 90,160 C 95,135 125,135 145,138" fill="#f5c7b3" stroke="#e09e82" stroke-width="2.5" stroke-linecap="round"/>

    
    
    <line x1="295" y1="178" x2="300" y2="212" stroke="#f43f5e" stroke-width="3" stroke-linecap="round"/>

    
    <g class="ossicles">
      
      <path d="M 300,195 L 320,180 L 324,188 L 305,203 Z" fill="#d97706"/>
      
      <path d="M 320,180 L 340,182 L 338,198 L 324,188 Z" fill="#f59e0b"/>
      
      <path d="M 338,198 L 358,198 M 345,193 L 358,193 M 345,203 L 358,203 M 358,190 L 358,206" stroke="#b45309" stroke-width="2.5" stroke-linecap="round"/>
    </g>

    
    <g transform="translate(372, 180)">
      
      <path d="M 40,25 C 40,5 25,-8 10,-5 C -5,-2 -12,12 -8,28 C -4,42 15,48 30,42 C 42,35 44,18 34,8 C 24,-2 10,2 6,14 C 2,24 14,30 22,26 C 26,24 28,18 24,14" fill="none" stroke="#8b5cf6" stroke-width="6" stroke-linecap="round"/>
      <circle cx="20" cy="20" r="3.5" fill="#7c3aed"/>
    </g>

    
    <g class="sound-group">
      
      <g class="sound-pulse">
        <path d="M 125,183 A 12 12 0 0 1 125,197" fill="none" stroke="#0284c7" stroke-width="3" stroke-linecap="round"/>
      </g>
      <g class="sound-pulse wave-2">
        <path d="M 125,183 A 12 12 0 0 1 125,197" fill="none" stroke="#0284c7" stroke-width="3" stroke-linecap="round"/>
      </g>
      <g class="sound-pulse wave-3">
        <path d="M 125,183 A 12 12 0 0 1 125,197" fill="none" stroke="#0284c7" stroke-width="3" stroke-linecap="round"/>
      </g>
    </g>

    
    <g class="impact-group">
      
      <g transform="translate(290, 48)">
        <path d="M 20,4 L 40,12 V 28 C 40,42 20,52 20,52 C 20,52 0,42 0,28 V 12 Z" fill="url(#shieldGrad)" opacity="0.95"/>
        <path d="M 12,25 L 18,31 L 29,19" fill="none" stroke="#ffffff" stroke-width="3" stroke-linecap="round" stroke-linejoin="round"/>
      </g>

      
      <g transform="translate(310, 8)">
        <text x="0" y="0" font-size="20" text-anchor="middle">👆</text>
        <path class="knock-wave" d="M -22,14 Q 0,24 22,14" fill="none" stroke="#f43f5e" stroke-width="3" stroke-linecap="round"/>
        <path class="knock-wave knock-2" d="M -30,20 Q 0,34 30,20" fill="none" stroke="#f43f5e" stroke-width="2" stroke-linecap="round"/>
      </g>
    </g>

    
    
    <g transform="translate(10, 275)">
      <rect x="0" y="0" width="128" height="28" rx="6" fill="#ffffff" stroke="#cbd5e1"/>
      <text x="64" y="18" font-size="13" font-weight="700" fill="#1e2945" text-anchor="middle">Outer Ear Flap</text>
      <path d="M 85,275 L 110,240" stroke="#64748b" stroke-width="1.5" stroke-dasharray="3,3"/>
    </g>

    
    <g transform="translate(240, 322)">
      <rect x="0" y="0" width="185" height="28" rx="6" fill="#ffffff" stroke="#cbd5e1"/>
      <text x="92" y="18" font-size="13" font-weight="700" fill="#1e2945" text-anchor="middle">Solid Skull Bone Shield</text>
      <path d="M 332,322 L 332,295" stroke="#64748b" stroke-width="1.5" stroke-dasharray="3,3"/>
    </g>

    
    <g transform="translate(345, 115)">
      <rect x="0" y="0" width="182" height="28" rx="6" fill="#ffffff" stroke="#cbd5e1"/>
      <text x="91" y="18" font-size="13" font-weight="700" fill="#1e2945" text-anchor="middle">Delicate Inner Ear Parts</text>
      <path d="M 410,143 L 385,170" stroke="#64748b" stroke-width="1.5" stroke-dasharray="3,3"/>
    </g>
  </svg>

  <script>
    function setMode(mode) {
      const isSound = mode === 'sound';
      document.body.className = isSound ? 'mode-sound' : 'mode-impact';
      document.getElementById('btnSound').classList.toggle('active', isSound);
      document.getElementById('btnImpact').classList.toggle('active', !isSound);
    }
  </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;
      user-select: none;
      -webkit-user-select: none;
    }

    body {
      width: 100%;
      background: #f8f9fa;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 12px;
    }

    .diagram-view {
      width: 100%;
      max-width: 520px;
      position: relative;
      display: flex;
      flex-direction: column;
      align-items: center;
    }

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

    .bone-label {
      font-size: 13px;
      font-weight: 700;
      fill: #1e2945;
      text-anchor: middle;
    }

    .sub-label {
      font-size: 11px;
      font-weight: 600;
      fill: #475569;
      text-anchor: middle;
    }

    /* Force wave animation along the bone curve */
    .force-wave {
      fill: none;
      stroke: #f59e0b;
      stroke-width: 6;
      stroke-linecap: round;
      stroke-dasharray: 40 180;
      stroke-dashoffset: 0;
      opacity: 0;
    }

    .animating .force-wave-left {
      animation: travelLeft 1.2s cubic-bezier(0.2, 0.8, 0.4, 1) forwards;
    }

    .animating .force-wave-right {
      animation: travelRight 1.2s cubic-bezier(0.2, 0.8, 0.4, 1) forwards;
    }

    @keyframes travelLeft {
      0% {
        opacity: 1;
        stroke-dashoffset: 60;
      }
      70% {
        opacity: 0.9;
      }
      100% {
        opacity: 0;
        stroke-dashoffset: 240;
      }
    }

    @keyframes travelRight {
      0% {
        opacity: 1;
        stroke-dashoffset: -60;
      }
      70% {
        opacity: 0.9;
      }
      100% {
        opacity: 0;
        stroke-dashoffset: -240;
      }
    }

    .impact-burst {
      opacity: 0;
      transform-origin: 250px 76px;
    }

    .animating .impact-burst {
      animation: burst 1.2s ease-out forwards;
    }

    @keyframes burst {
      0% {
        opacity: 0;
        transform: scale(0.3);
      }
      15% {
        opacity: 1;
        transform: scale(1.1);
      }
      40% {
        opacity: 0.8;
        transform: scale(1);
      }
      100% {
        opacity: 0;
        transform: scale(1.3);
      }
    }

    .brain-cushion {
      transition: transform 0.3s ease;
    }

    .controls {
      margin-top: 6px;
      display: flex;
      justify-content: center;
      width: 100%;
    }

    .btn {
      background: #2563eb;
      color: #ffffff;
      border: none;
      border-radius: 9999px;
      padding: 10px 22px;
      font-size: 14px;
      font-weight: 700;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 8px;
      box-shadow: 0 3px 10px rgba(37, 99, 235, 0.25);
      transition: background 0.2s, opacity 0.2s;
    }

    .btn:active {
      background: #1d4ed8;
    }

    .btn:disabled {
      opacity: 0.65;
      cursor: default;
    }
  </style>
</head>
<body>

  <div class="diagram-view" id="cranium">
    <svg viewBox="0 0 500 370" aria-label="Child Cranium Protection Diagram">
      <defs>
        
        <filter id="softGlow" x="-20%" y="-20%" width="140%" height="140%">
          <feDropShadow dx="0" dy="2" stdDeviation="3" flood-color="#000" flood-opacity="0.06"/>
        </filter>
      </defs>

      
      <path d="M 125 210 Q 110 250 135 285 Q 160 315 210 310 L 225 310" 
            fill="none" stroke="#cbd5e1" stroke-width="3" stroke-linecap="round"/>
      <path d="M 135 285 L 175 285" fill="none" stroke="#cbd5e1" stroke-width="2.5" stroke-linecap="round"/>

      
      <path d="M 120 205 C 110 135 170 90 250 90 C 335 90 395 145 385 220 C 375 275 305 295 240 295 C 170 295 130 255 120 205 Z" 
            fill="#e2e8f0" opacity="0.6"/>

      
      <g id="brainGroup" class="brain-cushion">
        
        <path d="M 132 202 C 124 146 176 104 250 104 C 324 104 376 150 370 214 C 362 264 300 282 245 282 C 182 282 140 248 132 202 Z" 
              fill="#fecdd3" stroke="#fda4af" stroke-width="3"/>
        
        
        <path d="M 320 250 C 350 252 360 278 340 290 C 320 298 300 285 300 270 Z" 
              fill="#fda4af" stroke="#fb7185" stroke-width="2"/>
        <path d="M 270 278 L 270 315 L 290 315 L 290 278 Z" 
              fill="#fbcfe8" stroke="#f472b6" stroke-width="2"/>

        
        <path d="M 160 180 Q 190 165 210 185 T 260 175 T 310 185 T 345 170" 
              fill="none" stroke="#fb7185" stroke-width="2.5" stroke-linecap="round"/>
        <path d="M 180 145 Q 215 130 245 148 T 315 140" 
              fill="none" stroke="#fb7185" stroke-width="2.5" stroke-linecap="round"/>
        <path d="M 175 220 Q 210 210 240 230 T 305 220 T 345 230" 
              fill="none" stroke="#fb7185" stroke-width="2.5" stroke-linecap="round"/>
      </g>

      
      
      <path d="M 106 208 C 96 142 142 74 218 68 
               C 219 92 216 112 219 135 C 216 158 220 178 217 205
               C 178 206 142 207 106 208 Z" 
            fill="#bae6fd" stroke="#0284c7" stroke-width="3.5" stroke-linejoin="round" filter="url(#softGlow)"/>

      
      <path d="M 218 68 C 265 65 315 80 348 108
               C 342 128 349 146 343 168 C 348 190 341 210 346 230
               C 300 228 260 216 217 205
               C 220 178 216 158 219 135 C 216 112 219 92 218 68 Z" 
            fill="#fef08a" stroke="#d97706" stroke-width="3.5" stroke-linejoin="round" filter="url(#softGlow)"/>

      
      <path d="M 348 108 C 388 142 405 192 396 248
               C 365 272 328 282 295 285
               C 306 260 326 245 346 230
               C 341 210 348 190 343 168 C 349 146 342 128 348 108 Z" 
            fill="#bbf7d0" stroke="#16a34a" stroke-width="3.5" stroke-linejoin="round" filter="url(#softGlow)"/>

      
      
      <path d="M 218 68 Q 215 80 219 92 Q 223 104 216 116 Q 221 128 219 140 Q 215 152 220 165 Q 223 178 217 190 Q 221 198 217 205" 
            fill="none" stroke="#0369a1" stroke-width="3" stroke-linecap="round"/>

      
      <path d="M 348 108 Q 343 120 347 132 Q 351 144 344 156 Q 348 168 344 180 Q 350 192 344 204 Q 349 216 346 230" 
            fill="none" stroke="#15803d" stroke-width="3" stroke-linecap="round"/>

      
      <path id="archLeft" class="force-wave force-wave-left" 
            d="M 250 66 C 185 68 108 115 106 208" />
      <path id="archRight" class="force-wave force-wave-right" 
            d="M 250 66 C 320 68 395 135 396 248" />

      
      <g id="impactBurst" class="impact-burst">
        <circle cx="250" cy="66" r="14" fill="#fbbf24" opacity="0.5"/>
        <circle cx="250" cy="66" r="7" fill="#f59e0b"/>
        
        <path d="M 250 44 L 250 54 M 232 50 L 240 57 M 268 50 L 260 57 M 225 66 L 235 66 M 275 66 L 265 66" 
              stroke="#d97706" stroke-width="3" stroke-linecap="round"/>
      </g>

      
      
      <text x="150" y="145" class="bone-label">Frontal</text>
      <text x="150" y="160" class="sub-label">Bone</text>

      
      <text x="278" y="135" class="bone-label">Parietal</text>
      <text x="278" y="150" class="sub-label">Bone</text>

      
      <text x="368" y="200" class="bone-label">Occipital</text>
      <text x="368" y="215" class="sub-label">Bone</text>

      
      <text x="245" y="254" class="bone-label" fill="#9f1239">Brain</text>
      <text x="245" y="268" class="sub-label" fill="#be123c">(Safe inside)</text>

      
      <path d="M 220 50 L 220 66" stroke="#475569" stroke-width="1.5" stroke-dasharray="2 2"/>
      <text x="220" y="42" class="sub-label" font-weight="700">Suture</text>
    </svg>

    
    <div class="controls">
      <button class="btn" id="impactBtn" onclick="triggerImpact()">
        <span>⚡ Tap Impact</span>
      </button>
    </div>
  </div>

  <script>
    function triggerImpact() {
      const container = document.getElementById('cranium');
      const btn = document.getElementById('impactBtn');
      
      // Remove class if currently active to allow instant re-trigger
      container.classList.remove('animating');
      btn.disabled = true;

      // Force layout reflow to restart CSS keyframes
      void container.offsetWidth;

      container.classList.add('animating');

      setTimeout(() => {
        btn.disabled = false;
      }, 1200);
    }
  </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;
      background: transparent;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
      padding: 12px;
      user-select: none;
    }

    .grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 12px;
      width: 100%;
      max-width: 580px;
    }

    .organ-card {
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 14px;
      padding: 14px 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      cursor: pointer;
      transition: border-color 0.3s ease, box-shadow 0.3s ease;
    }

    .organ-card.active {
      border-color: #0284c7;
      box-shadow: 0 0 0 3px rgba(2, 132, 199, 0.15), 0 8px 16px -4px rgba(2, 132, 199, 0.12);
    }

    .svg-box {
      width: 100%;
      max-width: 110px;
      aspect-ratio: 1 / 1;
      margin-bottom: 8px;
    }

    .bone-shield {
      transition: filter 0.3s ease, stroke-width 0.3s ease;
    }

    .organ-card.active .bone-shield {
      filter: drop-shadow(0 0 6px rgba(2, 132, 199, 0.6));
    }

    .bone-name {
      font-size: 15px;
      font-weight: 700;
      color: #0284c7;
      line-height: 1.2;
    }

    .label {
      font-size: 13px;
      font-weight: 600;
      color: #64748b;
      margin-top: 4px;
      line-height: 1.2;
    }

    .organ-card.active .label {
      color: #1e2945;
    }

    @media (max-width: 380px) {
      .grid {
        gap: 6px;
      }
      .organ-card {
        padding: 10px 4px;
      }
      .bone-name {
        font-size: 13px;
      }
      .label {
        font-size: 11px;
      }
    }
  </style>
</head>
<body>

  <div class="grid">
    
    <div class="organ-card active" onclick="selectCard(0)">
      <div class="svg-box">
        <svg viewBox="0 0 100 100" width="100%" height="100%">
          
          <ellipse cx="50" cy="52" rx="20" ry="17" fill="#f472b6" />
          <path d="M38 48 Q44 42 50 48 Q56 42 62 48" stroke="#db2777" stroke-width="2.5" fill="none" stroke-linecap="round" />
          <path d="M42 56 Q50 62 58 56" stroke="#db2777" stroke-width="2.5" fill="none" stroke-linecap="round" />
          
          <path class="bone-shield" d="M22 55 C20 22, 80 22, 78 55 C77 72, 68 80, 50 80 C32 80, 23 72, 22 55 Z" 
                fill="none" stroke="#0284c7" stroke-width="4.5" stroke-linejoin="round" />
          
          <path class="bone-shield" d="M36 68 Q41 62 46 68 M54 68 Q59 62 64 68" stroke="#0284c7" stroke-width="3" fill="none" stroke-linecap="round" />
        </svg>
      </div>
      <div class="bone-name">Skull</div>
      <div class="label">protects Brain</div>
    </div>

    
    <div class="organ-card" onclick="selectCard(1)">
      <div class="svg-box">
        <svg viewBox="0 0 100 100" width="100%" height="100%">
          
          <ellipse cx="37" cy="52" rx="11" ry="16" fill="#fda4af" />
          <ellipse cx="63" cy="52" rx="11" ry="16" fill="#fda4af" />
          
          <path d="M50 58 C50 58, 41 50, 41 44 C41 39, 46 38, 50 43 C54 38, 59 39, 59 44 C59 50, 50 58, 50 58 Z" fill="#ef4444" />
          
          <line class="bone-shield" x1="50" y1="26" x2="50" y2="76" stroke="#0284c7" stroke-width="4.5" stroke-linecap="round" />
          
          <path class="bone-shield" d="M22 38 Q50 30 78 38" stroke="#0284c7" stroke-width="3.5" fill="none" stroke-linecap="round" />
          <path class="bone-shield" d="M19 50 Q50 42 81 50" stroke="#0284c7" stroke-width="3.5" fill="none" stroke-linecap="round" />
          <path class="bone-shield" d="M22 62 Q50 54 78 62" stroke="#0284c7" stroke-width="3.5" fill="none" stroke-linecap="round" />
          <path class="bone-shield" d="M28 73 Q50 66 72 73" stroke="#0284c7" stroke-width="3.5" fill="none" stroke-linecap="round" />
        </svg>
      </div>
      <div class="bone-name">Rib Cage</div>
      <div class="label">protects<br>Heart & Lungs</div>
    </div>

    
    <div class="organ-card" onclick="selectCard(2)">
      <div class="svg-box">
        <svg viewBox="0 0 100 100" width="100%" height="100%">
          
          <line x1="50" y1="18" x2="50" y2="82" stroke="#fbbf24" stroke-width="6" stroke-linecap="round" />
          <line x1="50" y1="20" x2="50" y2="80" stroke="#fff" stroke-width="2" stroke-linecap="round" />
          
          <rect class="bone-shield" x="26" y="20" width="48" height="9" rx="3.5" fill="#f0f9ff" stroke="#0284c7" stroke-width="3" />
          <rect class="bone-shield" x="24" y="34" width="52" height="9" rx="3.5" fill="#f0f9ff" stroke="#0284c7" stroke-width="3" />
          <rect class="bone-shield" x="24" y="48" width="52" height="9" rx="3.5" fill="#f0f9ff" stroke="#0284c7" stroke-width="3" />
          <rect class="bone-shield" x="24" y="62" width="52" height="9" rx="3.5" fill="#f0f9ff" stroke="#0284c7" stroke-width="3" />
          <rect class="bone-shield" x="26" y="76" width="48" height="9" rx="3.5" fill="#f0f9ff" stroke="#0284c7" stroke-width="3" />
          
          <path d="M26 38 L16 41 M74 38 L84 41 M24 52 L14 55 M76 52 L86 55 M26 66 L16 69 M74 66 L84 69" stroke="#f59e0b" stroke-width="2" stroke-linecap="round" />
        </svg>
      </div>
      <div class="bone-name">Spine</div>
      <div class="label">protects<br>Spinal Cord</div>
    </div>
  </div>

  <script>
    const cards = document.querySelectorAll('.organ-card');
    let currentIndex = 0;
    let autoPlayTimer = null;

    function selectCard(index) {
      cards.forEach((card, i) => {
        card.classList.toggle('active', i === index);
      });
      currentIndex = index;
      resetAutoPlay();
    }

    function autoCycle() {
      currentIndex = (currentIndex + 1) % cards.length;
      selectCard(currentIndex);
    }

    function resetAutoPlay() {
      if (autoPlayTimer) clearInterval(autoPlayTimer);
      autoPlayTimer = setInterval(autoCycle, 3500);
    }

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

Functions of the Skeleton: Support, Protection, and Movement

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Arm Lever Mechanism</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #f8fafc;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      min-height: 100%;
      padding: 10px;
      user-select: none;
      overflow-x: hidden;
    }

    /* Badges header with responsive wrap & sizing */
    .flow-chain {
      display: flex;
      align-items: center;
      justify-content: center;
      flex-wrap: wrap;
      gap: 4px 6px;
      width: 100%;
      max-width: 420px;
      margin-bottom: 6px;
    }
    .badge {
      font-size: 11.5px;
      font-weight: 700;
      padding: 5px 9px;
      border-radius: 20px;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      color: #64748b;
      transition: all 0.3s ease;
      white-space: nowrap;
      text-align: center;
    }
    .badge.active-1 {
      background: #fff7ed;
      border-color: #f97316;
      color: #ea580c;
      box-shadow: 0 0 8px rgba(249, 115, 22, 0.25);
    }
    .badge.active-2 {
      background: #eff6ff;
      border-color: #3b82f6;
      color: #1d4ed8;
      box-shadow: 0 0 8px rgba(59, 130, 246, 0.25);
    }
    .badge.active-3 {
      background: #ecfdf5;
      border-color: #10b981;
      color: #047857;
      box-shadow: 0 0 8px rgba(16, 185, 129, 0.25);
    }
    .arrow-sep {
      color: #94a3b8;
      font-size: 11px;
      font-weight: 900;
    }

    @media (max-width: 375px) {
      .badge {
        font-size: 10.5px;
        padding: 4px 7px;
      }
      .arrow-sep {
        font-size: 9px;
      }
    }

    /* SVG Stage */
    .stage {
      position: relative;
      width: 100%;
      max-width: 420px;
      aspect-ratio: 1 / 0.82;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    svg {
      width: 100%;
      height: 100%;
      overflow: visible;
    }

    /* Controls */
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 10px;
      margin-top: 6px;
      width: 100%;
      max-width: 360px;
    }
    .btn {
      appearance: none;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #1e2945;
      padding: 7px 14px;
      font-size: 12.5px;
      font-weight: 600;
      border-radius: 8px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      box-shadow: 0 1px 2px rgba(0,0,0,0.05);
      transition: background 0.2s, border-color 0.2s;
    }
    .btn:active {
      background: #f1f5f9;
    }
    .btn.primary {
      background: #2563eb;
      color: #ffffff;
      border-color: #1d4ed8;
    }

    /* SVG Styling */
    .bone {
      fill: #e2e8f0;
      stroke: #64748b;
      stroke-width: 3;
      stroke-linejoin: round;
    }
    .joint-pivot {
      fill: #3b82f6;
      stroke: #ffffff;
      stroke-width: 3;
    }
    .muscle-bicep {
      fill: #f97316;
      stroke: #ea580c;
      stroke-width: 2.5;
      transition: fill 0.3s;
    }
    .label-text {
      font-size: 12px;
      font-weight: 700;
      fill: #475569;
      font-family: inherit;
    }
    .bicep-label {
      font-size: 12px;
      font-weight: 800;
      fill: #ea580c;
      paint-order: stroke fill;
      stroke: #ffffff;
      stroke-width: 3.5px;
      stroke-linejoin: round;
      stroke-linecap: round;
    }
    .motion-arc {
      fill: none;
      stroke: #10b981;
      stroke-width: 3;
      stroke-dasharray: 5, 4;
      transition: opacity 0.2s;
    }
  </style>
</head>
<body>

  
  <div class="flow-chain">
    <div id="b1" class="badge">1. Muscle pulls</div>
    <div class="arrow-sep">➔</div>
    <div id="b2" class="badge">2. Joint bends</div>
    <div class="arrow-sep">➔</div>
    <div id="b3" class="badge">3. Bone moves</div>
  </div>

  
  <div class="stage">
    <svg viewBox="0 0 400 310">
      <defs>
        
        <marker id="arrow" viewBox="0 0 10 10" refX="6" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1 L 8 5 L 0 9 z" fill="#10b981"/>
        </marker>
        <filter id="glow" x="-20%" y="-20%" width="140%" height="140%">
          <feDropShadow dx="0" dy="0" stdDeviation="4" flood-color="#f97316" flood-opacity="0.6"/>
        </filter>
      </defs>

      
      <path id="motionArc" class="motion-arc" d="M 330 220 A 180 180 0 0 0 255 95" marker-end="url(#arrow)" opacity="0.6" />

      
      <g id="upperArm">
        
        <rect x="90" y="24" width="40" height="24" rx="8" fill="#cbd5e1" stroke="#94a3b8" stroke-width="2" />
        
        <path class="bone" d="M 100 42 L 100 210 Q 100 220 110 220 Q 120 220 120 210 L 120 42 Z" />
        <text x="50" y="125" class="label-text" text-anchor="middle">Humerus</text>
        <line x1="75" y1="121" x2="98" y2="121" stroke="#94a3b8" stroke-width="1.5" stroke-dasharray="2 2" />
      </g>

      
      <path id="bicepPath" class="muscle-bicep" d="" />

      
      <g id="forearmGroup" transform="translate(110, 220)">
        
        <path class="bone" d="M 0 -12 L 180 -8 Q 195 0 180 8 L 0 12 Z" />
        
        
        <circle cx="190" cy="0" r="14" fill="#fed7aa" stroke="#fb923c" stroke-width="2" />
        
        
        <text x="105" y="28" class="label-text" text-anchor="middle">Radius / Ulna</text>
        
        
        <circle cx="45" cy="-8" r="4" fill="#ea580c" />
      </g>

      
      <circle cx="110" cy="220" r="12" class="joint-pivot" />
      <text x="110" y="256" class="label-text" text-anchor="middle">Elbow Joint</text>
      <text x="110" y="271" style="font-size: 10px; fill: #64748b; font-weight: 600;" text-anchor="middle">(Pivot)</text>

      
      <g id="topOverlay">
        <text id="bicepLabel" x="175" y="115" class="bicep-label">Bicep</text>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <button id="togglePlay" class="btn primary">⏸ Pause</button>
    <button id="stepAction" class="btn">Contract ➔</button>
  </div>

  <script>
    const forearm = document.getElementById('forearmGroup');
    const bicepPath = document.getElementById('bicepPath');
    const bicepLabel = document.getElementById('bicepLabel');
    const toggleBtn = document.getElementById('togglePlay');
    const stepBtn = document.getElementById('stepAction');
    const b1 = document.getElementById('b1');
    const b2 = document.getElementById('b2');
    const b3 = document.getElementById('b3');
    const motionArc = document.getElementById('motionArc');

    // Pivot constant
    const pivotX = 110;
    const pivotY = 220;
    const originBicepX = 110;
    const originBicepY = 52;

    let isPlaying = true;
    let progress = 0; // 0 = relaxed, 1 = fully contracted (-55 deg)
    let direction = 1;
    let manualTarget = null;

    function getForearmAngle(p) {
      return -55 * p;
    }

    function updateRig(p) {
      const angleDeg = getForearmAngle(p);
      const angleRad = (angleDeg * Math.PI) / 180;

      // Rotate Forearm
      forearm.setAttribute('transform', `translate(${pivotX}, ${pivotY}) rotate(${angleDeg})`);

      // Insertion point on forearm (local x=45, y=-8)
      const lx = 45, ly = -8;
      const insertX = pivotX + (lx * Math.cos(angleRad) - ly * Math.sin(angleRad));
      const insertY = pivotY + (lx * Math.sin(angleRad) + ly * Math.cos(angleRad));

      // Bicep geometry: bulges more as p increases
      const bulge = 14 + p * 16;
      const midX = (originBicepX + insertX) / 2 + bulge;
      const midY = (originBicepY + insertY) / 2;

      const backMidX = (originBicepX + insertX) / 2 - (bulge * 0.4);
      const backMidY = (originBicepY + insertY) / 2;

      const pathData = `
        M ${originBicepX} ${originBicepY}
        Q ${midX} ${midY} ${insertX} ${insertY}
        Q ${backMidX} ${backMidY} ${originBicepX} ${originBicepY}
        Z
      `;
      bicepPath.setAttribute('d', pathData);

      // Glow effect on active contraction
      if (p > 0.4) {
        bicepPath.setAttribute('filter', 'url(#glow)');
      } else {
        bicepPath.removeAttribute('filter');
      }

      // Position label safely along muscle bulge
      bicepLabel.setAttribute('x', midX + 10);
      bicepLabel.setAttribute('y', midY + 4);

      // Update badge states according to mechanical cause-and-effect
      b1.className = 'badge' + (p > 0.15 ? ' active-1' : '');
      b2.className = 'badge' + (p > 0.35 ? ' active-2' : '');
      b3.className = 'badge' + (p > 0.65 ? ' active-3' : '');
      motionArc.style.opacity = (p > 0.1 ? '0.8' : '0.2');
    }

    let lastTime = performance.now();

    function loop(time) {
      const dt = (time - lastTime) / 1000;
      lastTime = time;

      if (isPlaying) {
        // 2-second smooth full cycle
        progress += direction * (dt / 1.0);
        if (progress >= 1) {
          progress = 1;
          direction = -1;
        } else if (progress <= 0) {
          progress = 0;
          direction = 1;
        }
        updateRig(progress);
        stepBtn.textContent = direction > 0 ? 'Contracting...' : 'Relaxing...';
      } else if (manualTarget !== null) {
        const diff = manualTarget - progress;
        if (Math.abs(diff) < 0.02) {
          progress = manualTarget;
          manualTarget = null;
        } else {
          progress += Math.sign(diff) * dt * 2.0;
        }
        updateRig(progress);
      }

      requestAnimationFrame(loop);
    }

    requestAnimationFrame(loop);

    // Play/Pause button
    toggleBtn.addEventListener('click', () => {
      isPlaying = !isPlaying;
      toggleBtn.textContent = isPlaying ? '⏸ Pause' : '▶ Play';
      toggleBtn.className = isPlaying ? 'btn primary' : 'btn';
      if (!isPlaying) {
        stepBtn.textContent = progress > 0.5 ? 'Relax ➔' : 'Contract ➔';
      }
    });

    // Step toggle action
    stepBtn.addEventListener('click', () => {
      isPlaying = false;
      toggleBtn.textContent = '▶ Play';
      toggleBtn.className = 'btn';
      manualTarget = progress < 0.5 ? 1 : 0;
      stepBtn.textContent = manualTarget === 1 ? 'Relax ➔' : 'Contract ➔';
    });
  </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: #f8f9fa;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
    }
    .grid {
      display: flex;
      width: 100%;
      max-width: 600px;
      gap: 12px;
      justify-content: center;
      align-items: stretch;
      flex: 1;
    }
    .panel-box {
      flex: 1;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      text-align: center;
    }
    .title {
      font-size: 14px;
      font-weight: 700;
      line-height: 1.2;
    }
    .status-bad { color: #dc2626; font-size: 13px; font-weight: 600; }
    .status-good { color: #16a34a; font-size: 13px; font-weight: 600; }
    
    svg {
      width: 100%;
      max-height: 220px;
      overflow: visible;
    }

    .force-arrow {
      stroke: #2563eb;
      stroke-width: 2.5;
      stroke-linecap: round;
      transition: opacity 0.3s ease;
    }
    .force-active {
      animation: pulseArrow 1.5s infinite ease-in-out;
    }
    @keyframes pulseArrow {
      0%, 100% { opacity: 0.4; stroke-width: 2.5; }
      50% { opacity: 1; stroke-width: 3.5; }
    }

    .btn-toggle {
      background: #ffffff;
      border: 1.5px solid #2563eb;
      color: #2563eb;
      border-radius: 20px;
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      margin-top: 8px;
      display: inline-flex;
      align-items: center;
      gap: 6px;
    }
    .btn-toggle.active {
      background: #2563eb;
      color: #ffffff;
    }
  </style>
</head>
<body>

  <div class="grid">
    
    <div class="panel-box">
      <div class="title">
        Without Bones<br>
        <span class="status-bad">Collapses</span>
      </div>

      <svg viewBox="0 0 160 200">
        
        <line x1="10" y1="180" x2="150" y2="180" stroke="#cbd5e1" stroke-width="3" stroke-linecap="round"/>
        
        
        <path d="M 25 180 C 25 150, 45 130, 80 130 C 115 130, 135 150, 135 180 Z" fill="#60a5fa" opacity="0.85"/>
        <ellipse cx="80" cy="175" rx="55" ry="12" fill="#3b82f6"/>
        
        
        <path d="M 35 180 C 40 160, 60 155, 80 155 C 105 155, 120 160, 125 180 Z" fill="#93c5fd"/>
        
        
        <circle cx="70" cy="155" r="2.5" fill="#1e2945"/>
        <circle cx="90" cy="155" r="2.5" fill="#1e2945"/>
        <path d="M 74 168 Q 80 163 86 168" stroke="#1e2945" stroke-width="2" fill="none" stroke-linecap="round"/>

        
        <path class="collapse-ind" d="M 80 85 L 80 115 M 75 110 L 80 116 L 85 110" stroke="#dc2626" stroke-width="2" fill="none" stroke-linecap="round"/>
        <text x="80" y="75" text-anchor="middle" font-size="11" font-weight="bold" fill="#dc2626">No Support</text>
      </svg>
    </div>

    
    <div class="panel-box">
      <div class="title">
        With Bones<br>
        <span class="status-good">Stands Upright</span>
      </div>

      <svg viewBox="0 0 160 200">
        
        <line x1="10" y1="180" x2="150" y2="180" stroke="#cbd5e1" stroke-width="3" stroke-linecap="round"/>

        
        
        <circle cx="80" cy="32" r="14" fill="#e2e8f0" stroke="#475569" stroke-width="2"/>
        <circle cx="75" cy="30" r="2" fill="#475569"/>
        <circle cx="85" cy="30" r="2" fill="#475569"/>
        <line x1="77" y1="38" x2="83" y2="38" stroke="#475569" stroke-width="1.5" stroke-linecap="round"/>

        
        <line x1="80" y1="46" x2="80" y2="105" stroke="#475569" stroke-width="4" stroke-linecap="round"/>
        
        <path d="M 66 58 Q 80 62 94 58" stroke="#64748b" stroke-width="2" fill="none" stroke-linecap="round"/>
        <path d="M 64 68 Q 80 72 96 68" stroke="#64748b" stroke-width="2" fill="none" stroke-linecap="round"/>
        <path d="M 68 78 Q 80 82 92 78" stroke="#64748b" stroke-width="2" fill="none" stroke-linecap="round"/>

        
        <line x1="66" y1="58" x2="54" y2="92" stroke="#64748b" stroke-width="3" stroke-linecap="round"/>
        <line x1="94" y1="58" x2="106" y2="92" stroke="#64748b" stroke-width="3" stroke-linecap="round"/>

        
        <path d="M 68 105 Q 80 112 92 105" stroke="#475569" stroke-width="4" fill="none" stroke-linecap="round"/>

        
        
        <line x1="72" y1="108" x2="68" y2="145" stroke="#475569" stroke-width="3.5" stroke-linecap="round"/>
        <circle cx="68" cy="145" r="2" fill="#475569"/>
        <line x1="68" y1="145" x2="65" y2="180" stroke="#475569" stroke-width="3.5" stroke-linecap="round"/>
        
        
        <line x1="88" y1="108" x2="92" y2="145" stroke="#475569" stroke-width="3.5" stroke-linecap="round"/>
        <circle cx="92" cy="145" r="2" fill="#475569"/>
        <line x1="92" y1="145" x2="95" y2="180" stroke="#475569" stroke-width="3.5" stroke-linecap="round"/>

        
        <g id="supportArrows">
          
          <line x1="102" y1="52" x2="102" y2="96" class="force-arrow force-active"/>
          <polyline points="98,90 102,96 106,90" fill="none" class="force-arrow force-active"/>
          <text x="110" y="78" font-size="10" font-weight="700" fill="#2563eb">Spine</text>

          
          <line x1="112" y1="120" x2="112" y2="168" class="force-arrow force-active"/>
          <polyline points="108,162 112,168 116,162" fill="none" class="force-arrow force-active"/>
          <text x="119" y="148" font-size="10" font-weight="700" fill="#2563eb">Legs</text>
        </g>
      </svg>
    </div>
  </div>

  <button id="toggleBtn" class="btn-toggle active" onclick="toggleWeight()">
    <span>Support Forces</span> ⬇
  </button>

  <script>
    let active = true;
    function toggleWeight() {
      active = !active;
      const arrows = document.getElementById('supportArrows');
      const btn = document.getElementById('toggleBtn');
      if (active) {
        arrows.style.opacity = '1';
        btn.classList.add('active');
      } else {
        arrows.style.opacity = '0.15';
        btn.classList.remove('active');
      }
    }
  </script>
</body>
</html>

science.ks2.y1.t2.s2

Aligned learning resources

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