<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Point of Contact Diagram</title>
  <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: transparent;
      padding: 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
    }

    .container {
      width: 100%;
      max-width: 650px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    .header-text {
      text-align: center;
      margin-bottom: 2px;
    }

    .header-text h2 {
      font-size: 16px;
      font-weight: 700;
      color: #1e2945;
    }

    .header-text p {
      font-size: 12px;
      color: #64748b;
      margin-top: 2px;
    }

    .grid {
      display: flex;
      flex-wrap: wrap;
      gap: 12px;
      width: 100%;
    }

    .panel {
      flex: 1 1 270px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px 10px 14px;
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
    }

    .panel-a {
      border-top: 3px solid #ef4444;
    }

    .panel-b {
      border-top: 3px solid #22c55e;
    }

    .badge {
      display: inline-flex;
      align-items: center;
      gap: 5px;
      padding: 3px 10px;
      border-radius: 9999px;
      font-size: 12px;
      font-weight: 700;
      margin-bottom: 4px;
    }

    .badge-no {
      background: #fee2e2;
      color: #dc2626;
      border: 1px solid #fca5a5;
    }

    .badge-yes {
      background: #dcfce7;
      color: #15803d;
      border: 1px solid #86efac;
    }

    .scene-box {
      width: 100%;
      height: 155px;
      position: relative;
      display: flex;
      align-items: center;
      justify-content: center;
    }

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

    .caption {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      text-align: center;
      margin-top: 6px;
      line-height: 1.3;
    }

    .sub-caption {
      font-size: 11.5px;
      color: #64748b;
      font-weight: 500;
      margin-top: 2px;
      text-align: center;
    }

    /* Smooth, gentle motion animations (no flickering) */
    @keyframes smoothMotion {
      0%, 100% {
        transform: translateX(0);
      }
      50% {
        transform: translateX(6px);
      }
    }

    .moving-group {
      animation: smoothMotion 2.4s ease-in-out infinite;
    }

    @keyframes smoothGlow {
      0%, 100% {
        transform: scale(1);
        opacity: 0.65;
      }
      50% {
        transform: scale(1.18);
        opacity: 0.95;
      }
    }

    .glow-ring-outer {
      transform-origin: 136px 105px;
      animation: smoothGlow 2.4s ease-in-out infinite;
    }

    @media (max-width: 480px) {
      .scene-box {
        height: 140px;
      }
      .panel {
        padding: 10px 8px 12px;
      }
      .caption {
        font-size: 12px;
      }
      .sub-caption {
        font-size: 11px;
      }
    }
  </style>
</head>
<body>

  <div class="container">
    <div class="header-text">
      <h2>Contact Force & Point of Contact</h2>
      <p>A physical touch is required to apply a contact force</p>
    </div>

    <div class="grid">
      
      <div class="panel panel-a">
        <div class="badge badge-no">✕ Scenario A: No Touch</div>
        <div class="scene-box">
          <svg viewBox="0 0 280 155" aria-label="Scenario A: Sneaker hovering near soccer ball without touching">
            
            <defs>
              <linearGradient id="shoeGradA" x1="0%" y1="0%" x2="100%" y2="100%">
                <stop offset="0%" stop-color="#3b82f6" />
                <stop offset="100%" stop-color="#1d4ed8" />
              </linearGradient>
            </defs>

            
            <line x1="15" y1="135" x2="265" y2="135" stroke="#cbd5e1" stroke-width="2" stroke-dasharray="5 4" />
            <ellipse cx="65" cy="136" rx="42" ry="4" fill="#94a3b8" opacity="0.3" />
            <ellipse cx="205" cy="136" rx="30" ry="4" fill="#94a3b8" opacity="0.3" />

            
            <g transform="translate(18, 56)">
              
              <path d="M 22 4 L 22 28 L 38 25 L 38 4 Z" fill="#f1f5f9" stroke="#94a3b8" stroke-width="1.5" />
              <line x1="22" y1="11" x2="38" y2="11" stroke="#3b82f6" stroke-width="2" />

              
              <path d="M 16 30 C 11 44 9 58 9 68 L 92 68 C 95 65 94 56 86 52 C 77 47 67 40 52 26 C 45 20 38 24 34 26 C 26 29 18 29 16 30 Z" fill="url(#shoeGradA)" stroke="#1e40af" stroke-width="1.5" />

              
              <path d="M 20 54 Q 45 58 75 46 Q 50 63 22 61 Z" fill="#ffffff" opacity="0.9" />

              
              <path d="M 12 45 C 10 54 9 62 9 68 L 26 68 C 24 58 20 50 12 45 Z" fill="#1e40af" opacity="0.4" />

              
              <path d="M 33 26 C 36 21 44 20 48 24" fill="none" stroke="#0f172a" stroke-width="2.5" stroke-linecap="round" />
              
              
              <line x1="38" y1="28" x2="47" y2="33" stroke="#ffffff" stroke-width="2.5" stroke-linecap="round" />
              <line x1="44" y1="34" x2="54" y2="39" stroke="#ffffff" stroke-width="2.5" stroke-linecap="round" />
              <line x1="51" y1="40" x2="62" y2="45" stroke="#ffffff" stroke-width="2.5" stroke-linecap="round" />
              <line x1="59" y1="46" x2="70" y2="51" stroke="#ffffff" stroke-width="2.5" stroke-linecap="round" />

              
              <path d="M 7 68 L 93 68 C 96 68 97 73 94 75 L 7 75 C 5 75 5 68 7 68 Z" fill="#ffffff" stroke="#cbd5e1" stroke-width="1.5" />
              
              
              <path d="M 7 75 L 94 75 C 95 75 95 78 93 79 L 8 79 C 6 79 6 75 7 75 Z" fill="#0f172a" />
            </g>

            
            <g>
              <line x1="112" y1="95" x2="170" y2="95" stroke="#ef4444" stroke-width="1.5" stroke-dasharray="3 2" />
              <line x1="112" y1="88" x2="112" y2="102" stroke="#ef4444" stroke-width="1.5" />
              <line x1="170" y1="88" x2="170" y2="102" stroke="#ef4444" stroke-width="1.5" />
              <rect x="122" y="84" width="38" height="18" rx="4" fill="#fee2e2" stroke="#ef4444" stroke-width="1" />
              <text x="141" y="97" font-size="9" fill="#dc2626" font-weight="700" text-anchor="middle">2 in GAP</text>
            </g>

            
            <g transform="translate(170, 60)">
              <circle cx="35" cy="35" r="35" fill="#ffffff" stroke="#1e293b" stroke-width="2" />
              
              <polygon points="35,23 23,32 28,46 42,46 47,32" fill="#1e293b" />
              
              <line x1="35" y1="23" x2="35" y2="1" stroke="#1e293b" stroke-width="1.8" />
              <line x1="23" y1="32" x2="5" y2="23" stroke="#1e293b" stroke-width="1.8" />
              <line x1="28" y1="46" x2="13" y2="60" stroke="#1e293b" stroke-width="1.8" />
              <line x1="42" y1="46" x2="57" y2="60" stroke="#1e293b" stroke-width="1.8" />
              <line x1="47" y1="32" x2="65" y2="23" stroke="#1e293b" stroke-width="1.8" />
            </g>

            
            <text x="205" y="44" font-size="10" fill="#64748b" font-weight="600" text-anchor="middle">Ball is stationary</text>
          </svg>
        </div>
        <div class="caption">No Touch = No Force Applied</div>
        <div class="sub-caption">Ball stays completely still</div>
      </div>

      
      <div class="panel panel-b">
        <div class="badge badge-yes">✓ Scenario B: Contact Made</div>
        <div class="scene-box">
          <svg viewBox="0 0 280 155" aria-label="Scenario B: Sneaker touching soccer ball at point of contact">
            <defs>
              <linearGradient id="shoeGradB" x1="0%" y1="0%" x2="100%" y2="100%">
                <stop offset="0%" stop-color="#3b82f6" />
                <stop offset="100%" stop-color="#1d4ed8" />
              </linearGradient>
            </defs>

            
            <line x1="15" y1="135" x2="265" y2="135" stroke="#cbd5e1" stroke-width="2" stroke-dasharray="5 4" />
            <ellipse cx="88" cy="136" rx="42" ry="4" fill="#94a3b8" opacity="0.3" />
            
            
            <g transform="translate(42, 56)">
              
              <path d="M 22 4 L 22 28 L 38 25 L 38 4 Z" fill="#f1f5f9" stroke="#94a3b8" stroke-width="1.5" />
              <line x1="22" y1="11" x2="38" y2="11" stroke="#3b82f6" stroke-width="2" />

              
              <path d="M 16 30 C 11 44 9 58 9 68 L 92 68 C 95 65 94 56 86 52 C 77 47 67 40 52 26 C 45 20 38 24 34 26 C 26 29 18 29 16 30 Z" fill="url(#shoeGradB)" stroke="#1e40af" stroke-width="1.5" />

              
              <path d="M 20 54 Q 45 58 75 46 Q 50 63 22 61 Z" fill="#ffffff" opacity="0.9" />

              
              <path d="M 12 45 C 10 54 9 62 9 68 L 26 68 C 24 58 20 50 12 45 Z" fill="#1e40af" opacity="0.4" />

              
              <path d="M 33 26 C 36 21 44 20 48 24" fill="none" stroke="#0f172a" stroke-width="2.5" stroke-linecap="round" />
              
              
              <line x1="38" y1="28" x2="47" y2="33" stroke="#ffffff" stroke-width="2.5" stroke-linecap="round" />
              <line x1="44" y1="34" x2="54" y2="39" stroke="#ffffff" stroke-width="2.5" stroke-linecap="round" />
              <line x1="51" y1="40" x2="62" y2="45" stroke="#ffffff" stroke-width="2.5" stroke-linecap="round" />
              <line x1="59" y1="46" x2="70" y2="51" stroke="#ffffff" stroke-width="2.5" stroke-linecap="round" />

              
              <path d="M 7 68 L 93 68 C 96 68 97 73 94 75 L 7 75 C 5 75 5 68 7 68 Z" fill="#ffffff" stroke="#cbd5e1" stroke-width="1.5" />
              
              
              <path d="M 7 75 L 94 75 C 95 75 95 78 93 79 L 8 79 C 6 79 6 75 7 75 Z" fill="#0f172a" />
            </g>

            
            <g class="moving-group">
              
              <ellipse cx="170" cy="136" rx="30" ry="4" fill="#94a3b8" opacity="0.3" />

              
              <path d="M 212 75 Q 228 73 242 68" stroke="#3b82f6" stroke-width="2.5" stroke-linecap="round" fill="none" opacity="0.85" />
              <path d="M 215 95 Q 235 94 250 91" stroke="#3b82f6" stroke-width="2.5" stroke-linecap="round" fill="none" opacity="0.85" />
              <path d="M 212 115 Q 228 117 242 121" stroke="#3b82f6" stroke-width="2.5" stroke-linecap="round" fill="none" opacity="0.85" />

              
              <path d="M 218 50 L 244 50 M 238 45 L 245 50 L 238 55" stroke="#16a34a" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" />
              <text x="231" y="40" font-size="9" fill="#15803d" font-weight="700" text-anchor="middle">Force</text>

              
              <g transform="translate(135, 60)">
                <circle cx="35" cy="35" r="35" fill="#ffffff" stroke="#1e293b" stroke-width="2" />
                <polygon points="35,23 23,32 28,46 42,46 47,32" fill="#1e293b" />
                <line x1="35" y1="23" x2="35" y2="1" stroke="#1e293b" stroke-width="1.8" />
                <line x1="23" y1="32" x2="5" y2="23" stroke="#1e293b" stroke-width="1.8" />
                <line x1="28" y1="46" x2="13" y2="60" stroke="#1e293b" stroke-width="1.8" />
                <line x1="42" y1="46" x2="57" y2="60" stroke="#1e293b" stroke-width="1.8" />
                <line x1="47" y1="32" x2="65" y2="23" stroke="#1e293b" stroke-width="1.8" />
              </g>
            </g>

            
            <g>
              
              <circle class="glow-ring-outer" cx="136" cy="105" r="16" fill="#fef08a" opacity="0.75" />
              <circle cx="136" cy="105" r="9" fill="#eab308" opacity="0.9" />
              <circle cx="136" cy="105" r="3.5" fill="#ffffff" />

              
              <path d="M 136 94 L 136 34" stroke="#ca8a04" stroke-width="1.5" stroke-linecap="round" />
              <rect x="74" y="14" width="124" height="22" rx="11" fill="#fef9c3" stroke="#ca8a04" stroke-width="1.5" />
              <text x="136" y="29" font-size="10.5" fill="#854d0e" font-weight="700" text-anchor="middle">Point of Contact</text>
            </g>
          </svg>
        </div>
        <div class="caption">Touch = Contact Force Applied</div>
        <div class="sub-caption">Ball pushes forward and accelerates</div>
      </div>
    </div>
  </div>

</body>
</html>

Contact Forces: When Things Touch

<!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 {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #f8fafc;
      color: #0f172a;
      padding: 16px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100vh;
    }

    .container {
      width: 100%;
      max-width: 660px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .header-area {
      text-align: center;
    }

    .main-title {
      font-size: 18px;
      font-weight: 800;
      color: #0f172a;
      letter-spacing: -0.02em;
    }

    .sub-title {
      font-size: 13px;
      color: #475569;
      margin-top: 2px;
    }

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

    @media (max-width: 520px) {
      body {
        padding: 10px;
        min-height: auto;
      }
      .grid {
        grid-template-columns: 1fr;
        gap: 10px;
      }
      .main-title {
        font-size: 16px;
      }
    }

    .force-card {
      background: #ffffff;
      border: 2px solid #cbd5e1;
      border-radius: 12px;
      padding: 12px 10px 14px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      cursor: pointer;
      user-select: none;
      transition: border-color 0.2s ease, box-shadow 0.2s ease, background-color 0.2s ease;
      position: relative;
    }

    .force-card:hover {
      border-color: #0284c7;
      box-shadow: 0 4px 14px rgba(2, 132, 199, 0.12);
    }

    .force-card.active {
      border-color: #0284c7;
      background: #f0f9ff;
      box-shadow: 0 0 0 1px #0284c7, 0 4px 16px rgba(2, 132, 199, 0.16);
    }

    .card-title {
      font-size: 14px;
      font-weight: 700;
      margin-bottom: 8px;
      color: #0f172a;
    }

    .visual-area {
      position: relative;
      width: 100%;
      height: 94px;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-bottom: 10px;
      background: #f1f5f9;
      border-radius: 8px;
      overflow: hidden;
      border: 1px solid #e2e8f0;
    }

    .scene {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      z-index: 2;
    }

    /* Gentle pulsing highlight for contact zone (cycle >= 2s) */
    .contact-zone {
      position: absolute;
      width: 48px;
      height: 48px;
      border-radius: 50%;
      border: 3px solid #eab308;
      background: rgba(254, 240, 138, 0.45);
      pointer-events: none;
      z-index: 1;
      animation: gentle-pulse 2.2s infinite ease-in-out;
    }

    @keyframes gentle-pulse {
      0%, 100% {
        transform: scale(0.96);
        box-shadow: 0 0 0 3px rgba(234, 179, 8, 0.35);
        opacity: 0.85;
      }
      50% {
        transform: scale(1.08);
        box-shadow: 0 0 0 8px rgba(234, 179, 8, 0.2);
        opacity: 1;
      }
    }

    /* High-contrast category badges */
    .badge {
      display: inline-block;
      font-size: 11px;
      font-weight: 800;
      padding: 3px 10px;
      border-radius: 999px;
      margin-bottom: 8px;
      text-transform: uppercase;
      letter-spacing: 0.6px;
    }

    .badge-pull {
      background: #bae6fd;
      color: #075985;
      border: 1px solid #7dd3fc;
    }

    .badge-push {
      background: #fed7aa;
      color: #9a3412;
      border: 1px solid #fdba74;
    }

    .contact-label {
      font-size: 12.5px;
      color: #334155;
      font-weight: 600;
      line-height: 1.3;
      margin-bottom: 6px;
      min-height: 32px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    /* High contrast contact point pill */
    .touch-indicator {
      display: inline-flex;
      align-items: center;
      gap: 5px;
      font-size: 11px;
      color: #713f12;
      background: #fef08a;
      border: 1px solid #eab308;
      padding: 3px 8px;
      border-radius: 6px;
      font-weight: 700;
    }

    .touch-dot {
      width: 7px;
      height: 7px;
      border-radius: 50%;
      background: #ca8a04;
      display: inline-block;
    }

    .info-footer {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 8px 12px;
      font-size: 12px;
      color: #475569;
      text-align: center;
      line-height: 1.4;
    }
    
    .info-footer strong {
      color: #0f172a;
    }

    /* Tennis racket SVG styling */
    .racket-svg {
      width: 38px;
      height: 38px;
      transform: rotate(20deg);
      filter: drop-shadow(0 1px 2px rgba(0,0,0,0.15));
    }
  </style>
</head>
<body>

  <div class="container">
    <div class="header-area">
      <h1 class="main-title">Everyday Contact Forces</h1>
      <p class="sub-title">Contact forces occur when two physical objects directly touch each other.</p>
    </div>

    <div class="grid">
      
      <div class="force-card active" onclick="selectCard(this, 'pull', 'Zipping a Coat', 'Fingers exert a pull force by physically gripping and pulling the zipper slider.')">
        <div class="card-title">Zipping a Coat</div>
        <div class="visual-area">
          <div class="contact-zone"></div>
          <div class="scene">
            <span style="font-size: 26px;">🤏</span>
            <span style="font-size: 18px; color: #64748b; font-weight: bold;">⚡</span>
            <span style="font-size: 28px;">🧥</span>
          </div>
        </div>
        <div class="badge badge-pull">Type: Pull</div>
        <div class="contact-label">Fingers touch zipper</div>
        <div class="touch-indicator"><span class="touch-dot"></span>Touching Surfaces</div>
      </div>

      
      <div class="force-card" onclick="selectCard(this, 'push', 'Pressing a Doorbell', 'Your fingertip directly contacts and exerts a forward push against the doorbell button.')">
        <div class="card-title">Pressing a Doorbell</div>
        <div class="visual-area">
          <div class="contact-zone"></div>
          <div class="scene">
            <span style="font-size: 28px;">👉</span>
            <span style="font-size: 26px;">🔘</span>
          </div>
        </div>
        <div class="badge badge-push">Type: Push</div>
        <div class="contact-label">Finger touches button</div>
        <div class="touch-indicator"><span class="touch-dot"></span>Touching Surfaces</div>
      </div>

      
      <div class="force-card" onclick="selectCard(this, 'push', 'Hitting a Tennis Ball', 'The strung surface of the tennis racket collides directly with the tennis ball to push it forward.')">
        <div class="card-title">Hitting a Tennis Ball</div>
        <div class="visual-area">
          <div class="contact-zone"></div>
          <div class="scene">
            
            <svg class="racket-svg" viewBox="0 0 48 48" fill="none" xmlns="http://www.w3.org/2000/svg">
              
              <ellipse cx="28" cy="20" rx="14" ry="17" stroke="#dc2626" stroke-width="3" fill="#ffffff" />
              
              <line x1="16" y1="15" x2="40" y2="15" stroke="#94a3b8" stroke-width="1.2" />
              <line x1="15" y1="20" x2="41" y2="20" stroke="#94a3b8" stroke-width="1.2" />
              <line x1="17" y1="25" x2="39" y2="25" stroke="#94a3b8" stroke-width="1.2" />
              <line x1="23" y1="5" x2="23" y2="35" stroke="#94a3b8" stroke-width="1.2" />
              <line x1="28" y1="4" x2="28" y2="36" stroke="#94a3b8" stroke-width="1.2" />
              <line x1="33" y1="5" x2="33" y2="35" stroke="#94a3b8" stroke-width="1.2" />
              
              <path d="M21 34 L12 45 C11 46 9 46 8 45 L5 42 C4 41 4 39 5 38 L16 29" stroke="#1e293b" stroke-width="3.5" stroke-linecap="round" fill="#334155" />
              <rect x="7" y="38" width="10" height="4" transform="rotate(-45 7 38)" fill="#f8fafc" />
            </svg>
            <span style="font-size: 26px;">🎾</span>
          </div>
        </div>
        <div class="badge badge-push">Type: Push</div>
        <div class="contact-label">Racket strings touch ball</div>
        <div class="touch-indicator"><span class="touch-dot"></span>Touching Surfaces</div>
      </div>
    </div>

    
    <div class="info-footer" id="info-footer">
      <span id="detail-text"><strong>Zipping a Coat:</strong> Fingers exert a pull force by physically gripping and pulling the zipper slider. Yellow halo marks direct contact.</span>
    </div>
  </div>

  <script>
    function selectCard(el, type, title, detail) {
      document.querySelectorAll('.force-card').forEach(c => c.classList.remove('active'));
      el.classList.add('active');
      document.getElementById('detail-text').innerHTML = '<strong>' + title + ':</strong> ' + detail + ' Yellow halo marks direct contact.';
    }
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Push vs Pull</title>
  <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: #f8fafc;
      padding: 12px;
      display: flex;
      justify-content: center;
      align-items: center;
      min-height: 100vh;
    }
    .cards-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
      gap: 14px;
      width: 100%;
      max-width: 620px;
      margin: 0 auto;
    }
    .force-card {
      background: #ffffff;
      border-radius: 12px;
      padding: 16px 14px 12px 14px;
      box-shadow: 0 4px 12px rgba(30, 41, 69, 0.07), 0 1px 3px rgba(30, 41, 69, 0.04);
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
    }
    .card-header {
      text-align: center;
      margin-bottom: 8px;
    }
    .title-badge {
      display: inline-block;
      font-size: 15px;
      font-weight: 800;
      letter-spacing: 0.6px;
      text-transform: uppercase;
      padding: 4px 14px;
      border-radius: 20px;
      margin-bottom: 5px;
    }
    .push-badge {
      background: #15803d;
      color: #ffffff;
      box-shadow: 0 2px 4px rgba(21, 128, 61, 0.25);
    }
    .pull-badge {
      background: #c2410c;
      color: #ffffff;
      box-shadow: 0 2px 4px rgba(194, 65, 12, 0.25);
    }
    .action-label {
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
    }

    /* Scene Stage */
    .scene {
      width: 100%;
      height: 155px;
      position: relative;
    }
    svg {
      width: 100%;
      height: 100%;
      display: block;
    }

    /* Ground */
    .ground-line {
      stroke: #94a3b8;
      stroke-width: 3;
      stroke-linecap: round;
    }

    /* Directional Arrow Styling */
    .arrow-shaft {
      stroke-linecap: round;
    }
    .arrow-text {
      font-size: 11px;
      font-weight: 800;
      letter-spacing: 0.5px;
      text-transform: uppercase;
    }

    /* Animations */
    @keyframes pushCycle {
      0%, 15% {
        transform: translateX(0px);
      }
      60%, 80% {
        transform: translateX(34px);
      }
      95%, 100% {
        transform: translateX(0px);
      }
    }

    @keyframes pushArrow {
      0%, 15% {
        transform: translateX(0px) scale(0.96);
      }
      55%, 80% {
        transform: translateX(14px) scale(1.04);
      }
      95%, 100% {
        transform: translateX(0px) scale(0.96);
      }
    }

    @keyframes pullCycle {
      0%, 15% {
        transform: translateX(0px);
      }
      60%, 80% {
        transform: translateX(32px);
      }
      95%, 100% {
        transform: translateX(0px);
      }
    }

    @keyframes pullArrow {
      0%, 15% {
        transform: translateX(0px) scale(0.96);
      }
      55%, 80% {
        transform: translateX(14px) scale(1.04);
      }
      95%, 100% {
        transform: translateX(0px) scale(0.96);
      }
    }

    .moving-box {
      animation: pushCycle 3.4s ease-in-out infinite;
      transform-origin: center bottom;
    }
    .arrow-push {
      animation: pushArrow 3.4s ease-in-out infinite;
      transform-origin: 160px 28px;
    }

    .moving-wagon {
      animation: pullCycle 3.4s ease-in-out infinite;
      transform-origin: center bottom;
    }
    .arrow-pull {
      animation: pullArrow 3.4s ease-in-out infinite;
      transform-origin: 125px 28px;
    }
  </style>
</head>
<body>

  <div class="cards-grid">
    
    <div class="force-card">
      <div class="card-header">
        <span class="title-badge push-badge">Push</span>
        <div class="action-label">Moves away from you</div>
      </div>

      <div class="scene">
        <svg viewBox="0 0 280 150" aria-label="Illustration showing a child pushing a box away">
          
          <g class="arrow-push">
            <rect x="116" y="16" width="76" height="18" rx="4" fill="#15803d" />
            <polygon points="190,11 216,25 190,39" fill="#15803d" />
            <text x="154" y="29" fill="#ffffff" text-anchor="middle" class="arrow-text">PUSH ➔</text>
          </g>

          
          <line x1="15" y1="135" x2="265" y2="135" class="ground-line" />

          
          <g transform="translate(45, 45)">
            
            <circle cx="28" cy="18" r="14" fill="#fed7aa" stroke="#1e2945" stroke-width="2.5" />
            <path d="M 16 16 Q 28 6 38 12 Q 36 20 28 20" fill="#334155" />
            
            <line x1="28" y1="32" x2="38" y2="65" stroke="#1e2945" stroke-width="3.5" stroke-linecap="round" />
            <ellipse cx="33" cy="48" rx="9" ry="16" fill="#0284c7" stroke="#1e2945" stroke-width="2" transform="rotate(15 33 48)" />
            
            <line x1="38" y1="65" x2="18" y2="90" stroke="#1e2945" stroke-width="3.5" stroke-linecap="round" />
            <line x1="38" y1="65" x2="48" y2="90" stroke="#1e2945" stroke-width="3.5" stroke-linecap="round" />
            
            <line x1="32" y1="42" x2="68" y2="44" stroke="#1e2945" stroke-width="3.5" stroke-linecap="round" />
            
            <circle cx="70" cy="44" r="4" fill="#fed7aa" stroke="#1e2945" stroke-width="2" />
          </g>

          
          <g class="moving-box">
            <rect x="115" y="74" width="58" height="60" rx="4" fill="#d97706" stroke="#1e2945" stroke-width="2.5" />
            
            <line x1="117" y1="76" x2="171" y2="132" stroke="#92400e" stroke-width="2" />
            <line x1="171" y1="76" x2="117" y2="132" stroke="#92400e" stroke-width="2" />
            <rect x="122" y="81" width="44" height="46" fill="none" stroke="#fef3c7" stroke-width="1.5" />
          </g>
        </svg>
      </div>
    </div>

    
    <div class="force-card">
      <div class="card-header">
        <span class="title-badge pull-badge">Pull</span>
        <div class="action-label">Moves toward you</div>
      </div>

      <div class="scene">
        <svg viewBox="0 0 280 150" aria-label="Illustration showing a child pulling a wagon toward themselves">
          
          <g class="arrow-pull">
            <rect x="76" y="16" width="76" height="18" rx="4" fill="#c2410c" />
            <polygon points="150,11 176,25 150,39" fill="#c2410c" />
            <text x="114" y="29" fill="#ffffff" text-anchor="middle" class="arrow-text">PULL ➔</text>
          </g>

          
          <line x1="15" y1="135" x2="265" y2="135" class="ground-line" />

          
          <g transform="translate(185, 45)">
            
            <circle cx="28" cy="18" r="14" fill="#fde68a" stroke="#1e2945" stroke-width="2.5" />
            <path d="M 18 10 Q 28 4 38 12 Q 38 20 30 18" fill="#7c2d12" />
            
            <line x1="28" y1="32" x2="34" y2="65" stroke="#1e2945" stroke-width="3.5" stroke-linecap="round" />
            <ellipse cx="31" cy="48" rx="9" ry="16" fill="#9333ea" stroke="#1e2945" stroke-width="2" transform="rotate(10 31 48)" />
            
            <line x1="34" y1="65" x2="20" y2="90" stroke="#1e2945" stroke-width="3.5" stroke-linecap="round" />
            <line x1="34" y1="65" x2="48" y2="90" stroke="#1e2945" stroke-width="3.5" stroke-linecap="round" />
            
            <line x1="28" y1="44" x2="-2" y2="62" stroke="#1e2945" stroke-width="3.5" stroke-linecap="round" />
            
            <circle cx="-3" cy="62" r="4" fill="#fde68a" stroke="#1e2945" stroke-width="2" />
          </g>

          
          <g class="moving-wagon">
            
            <line x1="96" y1="112" x2="182" y2="107" stroke="#78350f" stroke-width="3" stroke-linecap="round" />
            
            
            <path d="M 40 98 L 96 98 L 92 120 L 44 120 Z" fill="#dc2626" stroke="#1e2945" stroke-width="2.5" />
            
            <circle cx="52" cy="125" r="9" fill="#f1f5f9" stroke="#1e2945" stroke-width="2.5" />
            <circle cx="52" cy="125" r="3" fill="#1e2945" />
            <circle cx="84" cy="125" r="9" fill="#f1f5f9" stroke="#1e2945" stroke-width="2.5" />
            <circle cx="84" cy="125" r="3" fill="#1e2945" />
          </g>
        </svg>
      </div>
    </div>
  </div>

</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;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 12px;
      user-select: none;
      -webkit-user-select: none;
    }

    .tab-bar {
      display: flex;
      gap: 8px;
      width: 100%;
      max-width: 420px;
      margin-bottom: 12px;
    }

    .tab-btn {
      flex: 1;
      padding: 8px 12px;
      font-size: 14px;
      font-weight: 600;
      background: #f1f5f9;
      border: 2px solid transparent;
      border-radius: 8px;
      color: #64748b;
      cursor: pointer;
      text-align: center;
      transition: all 0.2s ease;
    }

    .tab-btn.active {
      background: #e0f2fe;
      border-color: #0284c7;
      color: #0369a1;
    }

    .stage {
      position: relative;
      width: 100%;
      max-width: 420px;
      height: 320px;
      background: #f8fafc;
      border-radius: 12px;
      overflow: hidden;
      display: none;
    }

    .stage.active {
      display: block;
    }

    .controls {
      display: flex;
      justify-content: center;
      align-items: center;
      gap: 12px;
      width: 100%;
      max-width: 420px;
      margin-top: 10px;
    }

    .action-btn {
      padding: 8px 16px;
      font-size: 14px;
      font-weight: 600;
      background: #0284c7;
      color: #ffffff;
      border: none;
      border-radius: 8px;
      cursor: pointer;
      transition: background 0.2s ease;
    }

    .action-btn:active {
      background: #0369a1;
    }

    .slider-container {
      display: flex;
      align-items: center;
      gap: 10px;
      width: 100%;
      max-width: 320px;
    }

    .slider {
      flex: 1;
      height: 6px;
      accent-color: #0284c7;
      cursor: pointer;
    }

    /* SVG text stylings */
    .pole-text {
      font-size: 13px;
      font-weight: 800;
      fill: #ffffff;
      text-anchor: middle;
      dominant-baseline: central;
    }

    .badge-text {
      font-size: 14px;
      font-weight: 700;
      fill: #0369a1;
      text-anchor: middle;
    }
  </style>
</head>
<body>

  <div class="tab-bar">
    <button id="tab1Btn" class="tab-btn active" onclick="switchTab(1)">Floating Rings</button>
    <button id="tab2Btn" class="tab-btn" onclick="switchTab(2)">Through Table</button>
  </div>

  
  <div id="stage1" class="stage active">
    <svg id="svg1" viewBox="0 0 400 320" width="100%" height="100%">
      
      <ellipse cx="200" cy="285" rx="75" ry="16" fill="#cbd5e1" />
      <ellipse cx="200" cy="280" rx="75" ry="16" fill="#e2e8f0" />
      
      
      <rect x="194" y="35" width="12" height="245" rx="3" fill="#f59e0b" />
      <polygon points="194,35 206,35 200,15" fill="#fde68a" />
      <polygon points="198,20 202,20 200,15" fill="#1e293b" />
      <rect x="194" y="270" width="12" height="10" fill="#cbd5e1" />

      
      <g transform="translate(140, 220)">
        
        <path d="M 0,22 C 0,34 120,34 120,22 L 120,32 C 120,44 0,44 0,32 Z" fill="#1d4ed8" />
        <ellipse cx="60" cy="22" rx="60" ry="15" fill="#2563eb" />
        
        <path d="M 0,10 C 0,22 120,22 120,10 L 120,20 C 120,32 0,32 0,20 Z" fill="#b91c1c" />
        <ellipse cx="60" cy="10" rx="60" ry="15" fill="#dc2626" />
        
        <ellipse cx="60" cy="10" rx="14" ry="5" fill="#f59e0b" />
        <text x="60" y="23" class="pole-text">N</text>
      </g>

      
      <g id="forceField" opacity="1">
        <path d="M 160,185 Q 200,175 240,185" stroke="#0284c7" stroke-width="3" fill="none" stroke-dasharray="4,4" />
        <path d="M 150,195 Q 200,180 250,195" stroke="#0284c7" stroke-width="3" fill="none" stroke-dasharray="4,4" />
        <path d="M 165,205 Q 200,190 235,205" stroke="#0284c7" stroke-width="3" fill="none" stroke-dasharray="4,4" />
      </g>

      
      <g id="topMagnet" transform="translate(140, 110)" style="transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);">
        <g id="topMagnetPoles">
          
          <path d="M 0,22 C 0,34 120,34 120,22 L 120,32 C 120,44 0,44 0,32 Z" fill="#b91c1c" />
          <ellipse cx="60" cy="22" rx="60" ry="15" fill="#dc2626" />
          
          <path d="M 0,10 C 0,22 120,22 120,10 L 120,20 C 120,32 0,32 0,20 Z" fill="#1d4ed8" />
          <ellipse cx="60" cy="10" rx="60" ry="15" fill="#2563eb" />
          
          <ellipse cx="60" cy="10" rx="14" ry="5" fill="#f59e0b" />
          <text id="topLabelBottom" x="60" y="24" class="pole-text">N</text>
          <text id="topLabelTop" x="60" y="10" class="pole-text">S</text>
        </g>
      </g>

      
      <rect x="120" y="295" width="160" height="20" rx="10" fill="#e0f2fe" />
      <text id="statusText1" x="200" y="309" class="badge-text">Repelling Gap</text>
    </svg>
  </div>

  
  <div id="stage2" class="stage">
    <svg id="svg2" viewBox="0 0 400 320" width="100%" height="100%">
      
      <rect x="20" y="140" width="360" height="24" rx="4" fill="#d97706" />
      <rect x="20" y="140" width="360" height="6" fill="#f59e0b" />

      
      <g id="tableField" transform="translate(200, 150)">
        <ellipse cx="0" cy="0" rx="35" ry="45" fill="none" stroke="#38bdf8" stroke-width="2.5" stroke-dasharray="5,3" opacity="0.8" />
        <ellipse cx="0" cy="0" rx="20" ry="30" fill="none" stroke="#0284c7" stroke-width="2" stroke-dasharray="4,2" opacity="0.9" />
      </g>

      
      <g id="paperclip" transform="translate(200, 134)">
        <path d="M -18,0 L 12,0 C 18,0 18,-8 12,-8 L -14,-8 C -22,-8 -22,6 -14,6 L 16,6" 
              fill="none" stroke="#475569" stroke-width="3.5" stroke-linecap="round" stroke-linejoin="round" />
      </g>

      
      <g id="underMagnet" transform="translate(200, 175)">
        
        <rect x="-35" y="0" width="35" height="26" rx="3" fill="#dc2626" />
        <rect x="0" y="0" width="35" height="26" rx="3" fill="#2563eb" />
        <text x="-18" y="14" class="pole-text">N</text>
        <text x="18" y="14" class="pole-text">S</text>

        
        <g transform="translate(0, 26)">
          <path d="M -15,5 C -15,20 -5,35 -5,55 L 20,55 C 20,35 25,20 20,5 Z" fill="#fed7aa" />
          <ellipse cx="2" cy="10" rx="18" ry="8" fill="#fdba74" />
        </g>
      </g>

      
      <rect x="120" y="295" width="160" height="20" rx="10" fill="#e0f2fe" />
      <text x="200" y="309" class="badge-text">Non-Contact Force</text>
    </svg>
  </div>

  
  <div id="controls1" class="controls">
    <button class="action-btn" onclick="pushDown()">Push Down ⬇</button>
    <button class="action-btn" onclick="flipMagnet()">Flip Magnet ⇅</button>
  </div>

  <div id="controls2" class="controls" style="display: none;">
    <div class="slider-container">
      <span style="font-size: 18px;">✋</span>
      <input id="dragSlider" class="slider" type="range" min="80" max="320" value="200" oninput="moveHand(this.value)">
      <span style="font-size: 18px;">🧲</span>
    </div>
  </div>

  <script>
    let flipped = false;

    function switchTab(tab) {
      document.getElementById('tab1Btn').classList.toggle('active', tab === 1);
      document.getElementById('tab2Btn').classList.toggle('active', tab === 2);
      document.getElementById('stage1').classList.toggle('active', tab === 1);
      document.getElementById('stage2').classList.toggle('active', tab === 2);
      document.getElementById('controls1').style.display = tab === 1 ? 'flex' : 'none';
      document.getElementById('controls2').style.display = tab === 2 ? 'flex' : 'none';
    }

    function pushDown() {
      if (flipped) return;
      const topMag = document.getElementById('topMagnet');
      topMag.style.transform = 'translate(140px, 175px)';
      setTimeout(() => {
        topMag.style.transform = 'translate(140px, 110px)';
      }, 400);
    }

    function flipMagnet() {
      flipped = !flipped;
      const topMag = document.getElementById('topMagnet');
      const forceField = document.getElementById('forceField');
      const statusText = document.getElementById('statusText1');
      const topLabelTop = document.getElementById('topLabelTop');
      const topLabelBottom = document.getElementById('topLabelBottom');

      if (flipped) {
        // Attract (snaps down)
        topMag.style.transform = 'translate(140px, 192px)';
        forceField.style.opacity = '0';
        statusText.textContent = 'Attracting Poles';
        topLabelTop.textContent = 'N';
        topLabelBottom.textContent = 'S';
      } else {
        // Repel (floats)
        topMag.style.transform = 'translate(140px, 110px)';
        forceField.style.opacity = '1';
        statusText.textContent = 'Repelling Gap';
        topLabelTop.textContent = 'S';
        topLabelBottom.textContent = 'N';
      }
    }

    function moveHand(x) {
      document.getElementById('paperclip').setAttribute('transform', `translate(${x}, 134)`);
      document.getElementById('underMagnet').setAttribute('transform', `translate(${x}, 175)`);
      document.getElementById('tableField').setAttribute('transform', `translate(${x}, 150)`);
    }

    // Auto wobble for Tab 2 to guide learner
    let autoT = 0;
    let autoActive = true;
    function autoMove() {
      if (autoActive) {
        autoT += 0.03;
        const x = 200 + Math.sin(autoT) * 70;
        document.getElementById('dragSlider').value = x;
        moveHand(x);
        requestAnimationFrame(autoMove);
      }
    }
    autoMove();

    document.getElementById('dragSlider').addEventListener('pointerdown', () => {
      autoActive = false;
    });
  </script>
</body>
</html>

Exploring Non-Contact Forces: Action at a Distance

<!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: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 12px 16px;
      user-select: none;
      -webkit-user-select: none;
    }
    .stage-container {
      width: 100%;
      max-width: 580px;
      position: relative;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }
    .field-line {
      fill: none;
      stroke: #22b7ff;
      stroke-dasharray: 6 6;
      animation: fieldFlow 2.5s linear infinite;
    }
    @keyframes fieldFlow {
      to {
        stroke-dashoffset: -24;
      }
    }
    .controls {
      width: 100%;
      max-width: 440px;
      display: flex;
      flex-direction: column;
      gap: 8px;
      margin-top: 4px;
    }
    .slider-row {
      display: flex;
      align-items: center;
      gap: 12px;
    }
    .label {
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
      min-width: 65px;
    }
    input[type="range"] {
      flex: 1;
      height: 8px;
      border-radius: 4px;
      background: #e2e8f0;
      outline: none;
      -webkit-appearance: none;
      appearance: none;
      cursor: pointer;
    }
    input[type="range"]::-webkit-slider-thumb {
      -webkit-appearance: none;
      appearance: none;
      width: 24px;
      height: 24px;
      border-radius: 50%;
      background: #22b7ff;
      border: 2px solid #ffffff;
      box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
      cursor: pointer;
    }
    input[type="range"]::-moz-range-thumb {
      width: 24px;
      height: 24px;
      border-radius: 50%;
      background: #22b7ff;
      border: 2px solid #ffffff;
      box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
      cursor: pointer;
    }
    .meter-container {
      display: flex;
      align-items: center;
      gap: 12px;
    }
    .meter-track {
      flex: 1;
      height: 10px;
      background: #f1f5f9;
      border-radius: 5px;
      overflow: hidden;
      border: 1px solid #e2e8f0;
    }
    .meter-fill {
      height: 100%;
      width: 70%;
      background: linear-gradient(90deg, #22b7ff, #ef4444);
      border-radius: 5px;
      transition: width 0.1s ease-out;
    }
    .force-text {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      min-width: 60px;
      text-align: right;
    }
  </style>
</head>
<body>

  <div class="stage-container">
    <svg viewBox="0 0 540 280" id="magnetSvg">
      <defs>
        
        <radialGradient id="fieldGlow" cx="20%" cy="50%" r="70%">
          <stop offset="0%" stop-color="#22b7ff" stop-opacity="0.28" />
          <stop offset="60%" stop-color="#22b7ff" stop-opacity="0.08" />
          <stop offset="100%" stop-color="#22b7ff" stop-opacity="0" />
        </radialGradient>

        
        <radialGradient id="ballShade" cx="35%" cy="35%" r="65%">
          <stop offset="0%" stop-color="#ffffff" />
          <stop offset="40%" stop-color="#94a3b8" />
          <stop offset="100%" stop-color="#334155" />
        </radialGradient>

        
        <marker id="arrow" viewBox="0 0 10 10" refX="2" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 10 0 L 0 5 L 10 10 z" fill="#ef4444" />
        </marker>
      </defs>

      
      <ellipse cx="140" cy="140" rx="280" ry="135" fill="url(#fieldGlow)" />

      
      <text x="270" y="24" text-anchor="middle" fill="#0284c7" font-size="14" font-weight="700" letter-spacing="0.5">Magnetic Field</text>

      
      <g opacity="0.85">
        <path class="field-line" stroke-width="2.5" d="M 60 115 C 60 30, 260 25, 140 115" />
        <path class="field-line" stroke-width="2.5" d="M 60 165 C 60 250, 260 255, 140 165" />
        
        <path class="field-line" stroke-width="2" d="M 50 115 C 30 -10, 390 -10, 150 115" />
        <path class="field-line" stroke-width="2" d="M 50 165 C 30 290, 390 290, 150 165" />

        <path class="field-line" stroke-width="1.5" d="M 40 125 C -10 -40, 520 -30, 160 125" />
        <path class="field-line" stroke-width="1.5" d="M 40 155 C -10 320, 520 310, 160 155" />

        <line class="field-line" stroke-width="2" x1="160" y1="140" x2="520" y2="140" />
      </g>

      
      
      <path d="M 30 110 A 8 8 0 0 0 30 170 L 95 170 L 95 110 Z" fill="#ef4444" />
      <text x="60" y="147" fill="#ffffff" font-size="20" font-weight="800" text-anchor="middle">N</text>

      
      <path d="M 95 110 L 160 110 A 8 8 0 0 1 160 170 L 95 170 Z" fill="#2563eb" />
      <text x="130" y="147" fill="#ffffff" font-size="20" font-weight="800" text-anchor="middle">S</text>

      
      <g id="ballGroup" transform="translate(320, 140)">
        
        <line id="forceArrow" x1="-18" y1="0" x2="-75" y2="0" stroke="#ef4444" stroke-width="5" marker-end="url(#arrow)" stroke-linecap="round" />
        <text id="pullLabel" x="-45" y="-12" fill="#ef4444" font-size="13" font-weight="800" text-anchor="middle">Pull</text>

        
        <circle cx="0" cy="0" r="16" fill="url(#ballShade)" stroke="#475569" stroke-width="1" />
        <text x="0" y="32" fill="#1e2945" font-size="13" font-weight="700" text-anchor="middle">Steel Ball</text>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <div class="slider-row">
      <span class="label">Distance</span>
      <input type="range" id="distSlider" min="0" max="100" value="45" aria-label="Distance Slider">
    </div>
    <div class="meter-container">
      <span class="label">Pull Force</span>
      <div class="meter-track">
        <div class="meter-fill" id="meterFill"></div>
      </div>
      <span class="force-text" id="forceText">Strong</span>
    </div>
  </div>

  <script>
    const slider = document.getElementById('distSlider');
    const ballGroup = document.getElementById('ballGroup');
    const forceArrow = document.getElementById('forceArrow');
    const pullLabel = document.getElementById('pullLabel');
    const meterFill = document.getElementById('meterFill');
    const forceText = document.getElementById('forceText');

    function update() {
      const val = parseFloat(slider.value); // 0 (closest) to 100 (furthest)
      const ratio = val / 100; // 0 = close, 1 = far

      // Magnet right edge is at x=168. Range: 220 (close) to 480 (far)
      const ballX = 220 + ratio * 260;
      ballGroup.setAttribute('transform', `translate(${ballX}, 140)`);

      // Force scales non-linearly with distance
      const forceIntensity = Math.pow(1 - ratio, 1.6); // 1 = max force, ~0 = min force

      // Arrow visual scaling
      const arrowLength = 20 + forceIntensity * 75;
      const arrowWidth = 2 + forceIntensity * 5;
      forceArrow.setAttribute('x2', -arrowLength);
      forceArrow.setAttribute('stroke-width', arrowWidth);
      pullLabel.setAttribute('x', -arrowLength / 2);

      // Force Meter & Status Text
      const pct = Math.round(Math.max(6, forceIntensity * 100));
      meterFill.style.width = pct + '%';

      if (pct > 65) {
        forceText.textContent = 'Strong';
        forceText.style.color = '#ef4444';
      } else if (pct > 25) {
        forceText.textContent = 'Medium';
        forceText.style.color = '#f59e0b';
      } else {
        forceText.textContent = 'Weak';
        forceText.style.color = '#64748b';
      }
    }

    slider.addEventListener('input', update);
    update();
  </script>
</body>
</html>

science.ks2.y1.t5.s2

Aligned learning resources

Related diagrams