<!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: #1e293b;
      padding: 10px;
      display: flex;
      flex-direction: column;
      gap: 10px;
    }

    /* 3 Comparative Particle Cards */
    .cards-row {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 10px;
    }

    .particle-card {
      border-radius: 10px;
      padding: 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      border: 1.5px solid;
      background: #ffffff;
    }

    .card-proton {
      background: #fff1f2;
      border-color: #fecdd3;
    }

    .card-neutron {
      background: #f8fafc;
      border-color: #e2e8f0;
    }

    .card-electron {
      background: #f0f9ff;
      border-color: #bae6fd;
    }

    .card-header {
      display: flex;
      flex-direction: column;
      align-items: center;
    }

    .particle-avatar {
      width: 36px;
      height: 36px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 19px;
      font-weight: 800;
      color: #ffffff;
      margin-bottom: 4px;
      box-shadow: inset 0 -2px 4px rgba(0,0,0,0.18), 0 2px 4px rgba(0,0,0,0.08);
      flex-shrink: 0;
    }

    .avatar-proton {
      background: radial-gradient(circle at 35% 35%, #fb7185, #e11d48);
    }

    .avatar-neutron {
      background: radial-gradient(circle at 35% 35%, #94a3b8, #475569);
    }

    .avatar-electron {
      background: radial-gradient(circle at 35% 35%, #38bdf8, #0284c7);
      width: 26px;
      height: 26px;
      font-size: 15px;
      margin-top: 5px;
      margin-bottom: 9px;
    }

    .particle-title {
      font-size: 14px;
      font-weight: 700;
      margin-bottom: 6px;
    }

    .card-proton .particle-title { color: #be123c; }
    .card-neutron .particle-title { color: #334155; }
    .card-electron .particle-title { color: #0369a1; }

    .stat-list {
      width: 100%;
      display: flex;
      flex-direction: column;
      gap: 4px;
      font-size: 12px;
    }

    .stat-pill {
      background: rgba(255, 255, 255, 0.9);
      border-radius: 6px;
      padding: 4px 8px;
      display: flex;
      justify-content: space-between;
      align-items: center;
      gap: 8px;
      font-weight: 600;
      border: 1px solid rgba(0, 0, 0, 0.04);
    }

    .stat-label {
      color: #64748b;
      font-size: 11px;
      font-weight: 500;
      white-space: nowrap;
    }

    .stat-value {
      white-space: nowrap;
      text-align: right;
    }

    /* Bottom Mass Comparison Area */
    .balance-container {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 10px 10px;
      display: flex;
      flex-direction: column;
      gap: 6px;
    }

    .balance-title {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #64748b;
      text-align: center;
    }

    .scales-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
    }

    .scale-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 4px 4px;
      display: flex;
      flex-direction: column;
      align-items: center;
    }

    .scale-svg {
      width: 100%;
      max-height: 80px;
      display: block;
    }

    .scale-caption {
      font-size: 11px;
      font-weight: 700;
      margin-top: 2px;
      text-align: center;
    }

    .caption-equal {
      color: #475569;
    }

    .caption-light {
      color: #0284c7;
    }

    /* Responsive Mobile Layout */
    @media (max-width: 500px) {
      body {
        padding: 6px;
        gap: 8px;
      }

      .cards-row {
        grid-template-columns: 1fr;
        gap: 6px;
      }

      .particle-card {
        flex-direction: row;
        text-align: left;
        align-items: center;
        padding: 6px 10px;
        gap: 12px;
      }

      .card-header {
        flex-direction: column;
        align-items: center;
        justify-content: center;
        min-width: 58px;
      }

      .particle-avatar {
        width: 32px;
        height: 32px;
        font-size: 17px;
        margin-bottom: 2px;
      }

      .avatar-electron {
        width: 24px;
        height: 24px;
        font-size: 14px;
        margin-top: 4px;
        margin-bottom: 6px;
      }

      .particle-title {
        font-size: 12px;
        margin-bottom: 0;
      }

      .stat-list {
        display: grid;
        grid-template-columns: repeat(3, 1fr);
        gap: 5px;
      }

      .stat-pill {
        flex-direction: column;
        align-items: center;
        justify-content: center;
        padding: 4px 3px;
        gap: 1px;
        text-align: center;
      }

      .stat-label {
        font-size: 10px;
      }

      .stat-value {
        font-size: 11px;
        text-align: center;
      }

      .scale-caption {
        font-size: 10px;
      }
    }
  </style>
</head>
<body>

  
  <div class="cards-row">
    
    <div class="particle-card card-proton">
      <div class="card-header">
        <div class="particle-avatar avatar-proton">+</div>
        <div class="particle-title">Proton</div>
      </div>
      <div class="stat-list">
        <div class="stat-pill">
          <span class="stat-label">Charge</span>
          <span class="stat-value" style="color:#e11d48;">+1</span>
        </div>
        <div class="stat-pill">
          <span class="stat-label">Mass</span>
          <span class="stat-value">1</span>
        </div>
        <div class="stat-pill">
          <span class="stat-label">Location</span>
          <span class="stat-value">Nucleus</span>
        </div>
      </div>
    </div>

    
    <div class="particle-card card-neutron">
      <div class="card-header">
        <div class="particle-avatar avatar-neutron">0</div>
        <div class="particle-title">Neutron</div>
      </div>
      <div class="stat-list">
        <div class="stat-pill">
          <span class="stat-label">Charge</span>
          <span class="stat-value" style="color:#475569;">0</span>
        </div>
        <div class="stat-pill">
          <span class="stat-label">Mass</span>
          <span class="stat-value">1</span>
        </div>
        <div class="stat-pill">
          <span class="stat-label">Location</span>
          <span class="stat-value">Nucleus</span>
        </div>
      </div>
    </div>

    
    <div class="particle-card card-electron">
      <div class="card-header">
        <div class="particle-avatar avatar-electron">−</div>
        <div class="particle-title">Electron</div>
      </div>
      <div class="stat-list">
        <div class="stat-pill">
          <span class="stat-label">Charge</span>
          <span class="stat-value" style="color:#0284c7;">−1</span>
        </div>
        <div class="stat-pill">
          <span class="stat-label">Mass</span>
          <span class="stat-value" style="font-size:11px;"><sup>1</sup>/<sub>1840</sub></span>
        </div>
        <div class="stat-pill">
          <span class="stat-label">Location</span>
          <span class="stat-value">Shells</span>
        </div>
      </div>
    </div>
  </div>

  
  <div class="balance-container">
    <div class="balance-title">Relative Mass Comparison</div>
    <div class="scales-grid">
      
      <div class="scale-card">
        <svg class="scale-svg" viewBox="0 0 220 85" xmlns="http://www.w3.org/2000/svg">
          <defs>
            <radialGradient id="pGrad" cx="35%" cy="35%">
              <stop offset="0%" stop-color="#fb7185"/>
              <stop offset="100%" stop-color="#e11d48"/>
            </radialGradient>
            <radialGradient id="nGrad" cx="35%" cy="35%">
              <stop offset="0%" stop-color="#94a3b8"/>
              <stop offset="100%" stop-color="#475569"/>
            </radialGradient>
          </defs>
          
          <polygon points="110,42 98,76 122,76" fill="#94a3b8" />
          <rect x="85" y="74" width="50" height="4" rx="2" fill="#64748b" />
          
          <line x1="30" y1="42" x2="190" y2="42" stroke="#475569" stroke-width="3.5" stroke-linecap="round" />
          <circle cx="110" cy="42" r="3.5" fill="#334155" />
          
          
          <line x1="42" y1="42" x2="28" y2="60" stroke="#94a3b8" stroke-width="1.2" />
          <line x1="42" y1="42" x2="56" y2="60" stroke="#94a3b8" stroke-width="1.2" />
          <path d="M 22 60 Q 42 68 62 60 Z" fill="#cbd5e1" />
          <circle cx="42" cy="52" r="9" fill="url(#pGrad)" />
          <text x="42" y="55.5" font-size="10" font-weight="bold" fill="#ffffff" text-anchor="middle">+</text>

          
          <line x1="178" y1="42" x2="164" y2="60" stroke="#94a3b8" stroke-width="1.2" />
          <line x1="178" y1="42" x2="192" y2="60" stroke="#94a3b8" stroke-width="1.2" />
          <path d="M 158 60 Q 178 68 198 60 Z" fill="#cbd5e1" />
          <circle cx="178" cy="52" r="9" fill="url(#nGrad)" />
          <text x="178" y="55.5" font-size="9.5" font-weight="bold" fill="#ffffff" text-anchor="middle">0</text>
        </svg>
        <div class="scale-caption caption-equal">Mass 1 = Mass 1 (Balanced)</div>
      </div>

      
      <div class="scale-card">
        <svg class="scale-svg" viewBox="0 0 220 85" xmlns="http://www.w3.org/2000/svg">
          <defs>
            <radialGradient id="eGrad" cx="35%" cy="35%">
              <stop offset="0%" stop-color="#38bdf8"/>
              <stop offset="100%" stop-color="#0284c7"/>
            </radialGradient>
          </defs>
          
          <polygon points="110,42 98,76 122,76" fill="#94a3b8" />
          <rect x="85" y="74" width="50" height="4" rx="2" fill="#64748b" />
          
          <line x1="32" y1="56" x2="188" y2="28" stroke="#475569" stroke-width="3.5" stroke-linecap="round" />
          <circle cx="110" cy="42" r="3.5" fill="#334155" />

          
          <line x1="44" y1="54" x2="30" y2="72" stroke="#94a3b8" stroke-width="1.2" />
          <line x1="44" y1="54" x2="58" y2="72" stroke="#94a3b8" stroke-width="1.2" />
          <path d="M 24 72 Q 44 80 64 72 Z" fill="#cbd5e1" />
          <circle cx="44" cy="64" r="9" fill="url(#pGrad)" />
          <text x="44" y="67.5" font-size="10" font-weight="bold" fill="#ffffff" text-anchor="middle">+</text>

          
          <line x1="176" y1="30" x2="162" y2="48" stroke="#94a3b8" stroke-width="1.2" />
          <line x1="176" y1="30" x2="190" y2="48" stroke="#94a3b8" stroke-width="1.2" />
          <path d="M 156 48 Q 176 56 196 48 Z" fill="#cbd5e1" />
          <circle cx="176" cy="44" r="3.5" fill="url(#eGrad)" />
        </svg>
        <div class="scale-caption caption-light">Electron is 1840× Lighter</div>
      </div>
    </div>
  </div>

</body>
</html>

Subatomic Particles: Protons, Neutrons, and Electrons

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }

    body {
      width: 100%;
      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%;
    }

    .main-stage {
      width: 100%;
      max-width: 440px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 12px;
    }

    /* Mode Selector */
    .controls {
      display: flex;
      gap: 8px;
      width: 100%;
      justify-content: center;
    }

    .tab-btn {
      flex: 1;
      max-width: 160px;
      padding: 8px 12px;
      font-size: 14px;
      font-weight: 600;
      border: 1px solid #e2e8f0;
      background: #f8fafc;
      color: #64748b;
      border-radius: 8px;
      cursor: pointer;
      text-align: center;
      transition: background 0.2s, color 0.2s, box-shadow 0.2s;
    }

    .tab-btn.active {
      background: #ffffff;
      color: #0284c7;
      border-color: #0284c7;
      box-shadow: 0 0 0 1px #0284c7;
    }

    /* Atom Visual Container */
    .atom-viewport {
      position: relative;
      width: 100%;
      max-width: 260px;
      aspect-ratio: 1 / 1;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    .orbit-ring {
      position: absolute;
      width: 82%;
      height: 82%;
      border: 1.5px dashed #cbd5e1;
      border-radius: 50%;
      animation: rotateOrbit 16s linear infinite;
    }

    @keyframes rotateOrbit {
      from { transform: rotate(0deg); }
      to { transform: rotate(360deg); }
    }

    /* Electron on orbit */
    .electron {
      position: absolute;
      width: 22px;
      height: 22px;
      border-radius: 50%;
      background: #0284c7;
      color: #ffffff;
      font-size: 14px;
      font-weight: 700;
      display: flex;
      align-items: center;
      justify-content: center;
      box-shadow: 0 2px 5px rgba(2, 132, 199, 0.3);
      transition: transform 0.3s ease, filter 0.3s ease;
    }

    .e-top {
      top: -11px;
      left: calc(50% - 11px);
    }

    .e-bottom {
      bottom: -11px;
      left: calc(50% - 11px);
    }

    /* Central Nucleus */
    .nucleus {
      position: relative;
      width: 86px;
      height: 86px;
      border-radius: 50%;
      background: #f1f5f9;
      border: 1px solid #e2e8f0;
      display: grid;
      grid-template-columns: 1fr 1fr;
      padding: 10px;
      gap: 4px;
      align-items: center;
      justify-items: center;
      box-shadow: inset 0 2px 6px rgba(0,0,0,0.04);
      z-index: 2;
    }

    .particle {
      width: 28px;
      height: 28px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 14px;
      font-weight: 700;
      color: #ffffff;
      transition: filter 0.3s ease;
    }

    .proton {
      background: #6366f1;
      box-shadow: 0 2px 4px rgba(99, 102, 241, 0.3);
    }

    .neutron {
      background: #64748b;
      box-shadow: 0 2px 4px rgba(100, 116, 139, 0.3);
    }

    /* Dimming inactive particles */
    .dimmed {
      opacity: 0.25;
      filter: grayscale(80%);
    }

    .highlight-ring {
      box-shadow: 0 0 0 3px #38bdf8;
    }

    /* Math Cards Section */
    .calc-container {
      width: 100%;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    .calc-card {
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 10px 14px;
      background: #f8fafc;
      transition: border-color 0.3s, background 0.3s, box-shadow 0.3s;
    }

    .calc-card.active {
      background: #ffffff;
      border-color: #0284c7;
      box-shadow: 0 2px 8px rgba(2, 132, 199, 0.08);
    }

    .calc-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
      margin-bottom: 6px;
    }

    .badge {
      font-size: 13px;
      padding: 2px 8px;
      border-radius: 6px;
      font-weight: 600;
    }

    .badge-mass {
      background: #e0e7ff;
      color: #4338ca;
    }

    .badge-charge {
      background: #e0f2fe;
      color: #0369a1;
    }

    .calc-formula {
      font-size: 14px;
      color: #475569;
      line-height: 1.4;
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      gap: 4px;
    }

    .item {
      display: inline-flex;
      align-items: center;
      gap: 3px;
      padding: 2px 5px;
      border-radius: 4px;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      font-size: 13px;
      font-weight: 500;
    }

    .total {
      font-weight: 700;
      color: #0f172a;
      margin-left: 2px;
    }

    .dot-p { width: 8px; height: 8px; border-radius: 50%; background: #6366f1; }
    .dot-n { width: 8px; height: 8px; border-radius: 50%; background: #64748b; }
    .dot-e { width: 8px; height: 8px; border-radius: 50%; background: #0284c7; }
  </style>
</head>
<body>

  <div class="main-stage">
    
    <div class="controls">
      <button class="tab-btn active" id="btnMass" onclick="setMode('mass')">Mass Calculation</button>
      <button class="tab-btn" id="btnCharge" onclick="setMode('charge')">Net Charge</button>
    </div>

    
    <div class="atom-viewport">
      
      <div class="orbit-ring" id="orbitRing">
        <div class="electron e-top" title="Electron (−)">−</div>
        <div class="electron e-bottom" title="Electron (−)">−</div>
      </div>

      
      <div class="nucleus" id="nucleus">
        <div class="particle proton" title="Proton (+)">+</div>
        <div class="particle neutron" title="Neutron (0)">0</div>
        <div class="particle neutron" title="Neutron (0)">0</div>
        <div class="particle proton" title="Proton (+)">+</div>
      </div>
    </div>

    
    <div class="calc-container">
      
      <div class="calc-card active" id="cardMass" onclick="setMode('mass')">
        <div class="calc-header">
          <span>Total Mass</span>
          <span class="badge badge-mass">4 amu</span>
        </div>
        <div class="calc-formula">
          <span class="item"><span class="dot-p"></span>2p × 1</span> +
          <span class="item"><span class="dot-n"></span>2n × 1</span> +
          <span class="item"><span class="dot-e"></span>2e × 0</span>
          <span>=</span>
          <span class="total">4</span>
        </div>
      </div>

      
      <div class="calc-card" id="cardCharge" onclick="setMode('charge')">
        <div class="calc-header">
          <span>Net Charge</span>
          <span class="badge badge-charge">0 (Neutral)</span>
        </div>
        <div class="calc-formula">
          <span class="item"><span class="dot-p"></span>Nucleus (+2)</span> +
          <span class="item"><span class="dot-e"></span>Electrons (−2)</span>
          <span>=</span>
          <span class="total">0</span>
        </div>
      </div>
    </div>
  </div>

  <script>
    function setMode(mode) {
      const isMass = mode === 'mass';
      
      document.getElementById('btnMass').classList.toggle('active', isMass);
      document.getElementById('btnCharge').classList.toggle('active', !isMass);

      document.getElementById('cardMass').classList.toggle('active', isMass);
      document.getElementById('cardCharge').classList.toggle('active', !isMass);

      const neutrons = document.querySelectorAll('.neutron');
      neutrons.forEach(n => {
        n.classList.toggle('dimmed', !isMass);
      });

      const electrons = document.querySelectorAll('.electron');
      electrons.forEach(e => {
        e.classList.toggle('dimmed', isMass);
      });
    }

    // Auto-cycle gently every 4.5 seconds so both calculations are demonstrated
    let autoInterval = setInterval(() => {
      const isMassActive = document.getElementById('btnMass').classList.contains('active');
      setMode(isMassActive ? 'charge' : 'mass');
    }, 4500);

    // Pause auto-cycle on manual tap
    document.querySelectorAll('.tab-btn, .calc-card').forEach(el => {
      el.addEventListener('click', () => {
        clearInterval(autoInterval);
      });
    });

    // Initialize state
    setMode('mass');
  </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>Atom Structure Diagram</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      background: #f8f9fa;
      color: #1e2945;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100vh;
      padding: 12px;
      user-select: none;
      -webkit-user-select: none;
    }
    .main-view {
      width: 100%;
      max-width: 420px;
      aspect-ratio: 1 / 1;
      position: relative;
    }
    svg {
      width: 100%;
      height: 100%;
      display: block;
      overflow: visible;
    }
    .orbit {
      fill: none;
      stroke: #cbd5e1;
      stroke-width: 1.5;
      stroke-dasharray: 4 4;
      transition: stroke 0.3s ease, stroke-width 0.3s ease;
    }
    .orbit.active {
      stroke: #0284c7;
      stroke-width: 2;
      stroke-dasharray: none;
    }
    .orbit-group-1 {
      transform-origin: 200px 200px;
      animation: spin 10s linear infinite;
      will-change: transform;
    }
    .orbit-group-2 {
      transform-origin: 200px 200px;
      animation: spin-reverse 16s linear infinite;
      will-change: transform;
    }
    @keyframes spin {
      0% { transform: rotate(0deg); }
      100% { transform: rotate(360deg); }
    }
    @keyframes spin-reverse {
      0% { transform: rotate(0deg); }
      100% { transform: rotate(-360deg); }
    }
    .particle {
      transition: opacity 0.3s ease, filter 0.3s ease;
    }
    .dimmed {
      opacity: 0.2;
    }
    .highlighted {
      filter: drop-shadow(0 0 6px currentColor);
    }
    .label-box {
      font-family: inherit;
    }
    .label-title {
      font-size: 13px;
      font-weight: 700;
      fill: #1e2945;
      letter-spacing: -0.2px;
    }
    .label-sub {
      font-size: 11px;
      font-weight: 500;
      fill: #64748b;
    }
    .pointer-line {
      fill: none;
      stroke: #64748b;
      stroke-width: 1.5;
      stroke-linecap: round;
      stroke-linejoin: round;
    }
    .pointer-dot {
      fill: #64748b;
    }
    .ctrl-bar {
      display: flex;
      gap: 6px;
      margin-top: 10px;
      flex-wrap: wrap;
      justify-content: center;
      max-width: 420px;
    }
    .btn {
      appearance: none;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #1e2945;
      font-size: 12px;
      font-weight: 600;
      padding: 6px 12px;
      border-radius: 20px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease;
    }
    .btn:hover {
      background-color: #f1f5f9;
      border-color: #94a3b8;
    }
    .btn.active {
      background-color: #1e2945;
      color: #ffffff;
      border-color: #1e2945;
    }
    .dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
      display: inline-block;
    }
    .dot-p { background: #ef4444; }
    .dot-n { background: #94a3b8; }
    .dot-e { background: #0284c7; }
  </style>
</head>
<body>
  <div class="main-view">
    <svg viewBox="0 0 400 400" aria-label="Atom layout diagram showing nucleus and electron shells">
      
      <circle id="orbit1" class="orbit" cx="200" cy="200" r="85" />
      <circle id="orbit2" class="orbit" cx="200" cy="200" r="135" />

      
      <g class="orbit-group-1">
        <g class="particle electron" style="color: #0284c7;">
          <circle cx="200" cy="115" r="10" fill="#0284c7" />
          <text x="200" y="121.5" font-size="14" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">−</text>
        </g>
        <g class="particle electron" style="color: #0284c7;">
          <circle cx="200" cy="285" r="10" fill="#0284c7" />
          <text x="200" y="291.5" font-size="14" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">−</text>
        </g>
      </g>

      
      <g class="orbit-group-2">
        <g class="particle electron" style="color: #0284c7;">
          <circle cx="335" cy="200" r="10" fill="#0284c7" />
          <text x="335" y="206.5" font-size="14" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">−</text>
        </g>
      </g>

      
      <g id="nucleusGroup">
        
        <g class="particle neutron" style="color: #64748b;">
          <circle cx="189" cy="191" r="14" fill="#94a3b8" />
          <text x="189" y="195.5" font-size="13" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">0</text>
        </g>
        <g class="particle neutron" style="color: #64748b;">
          <circle cx="213" cy="209" r="14" fill="#94a3b8" />
          <text x="213" y="213.5" font-size="13" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">0</text>
        </g>
        <g class="particle neutron" style="color: #64748b;">
          <circle cx="198" cy="219" r="14" fill="#94a3b8" />
          <text x="198" y="223.5" font-size="13" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">0</text>
        </g>

        
        <g class="particle proton" style="color: #dc2626;">
          <circle cx="211" cy="187" r="14" fill="#ef4444" />
          <text x="211" y="191.5" font-size="16" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">+</text>
        </g>
        <g class="particle proton" style="color: #dc2626;">
          <circle cx="183" cy="211" r="14" fill="#ef4444" />
          <text x="183" y="215.5" font-size="16" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">+</text>
        </g>
        <g class="particle proton" style="color: #dc2626;">
          <circle cx="203" cy="199" r="14" fill="#ef4444" />
          <text x="203" y="203.5" font-size="16" font-weight="bold" fill="#ffffff" text-anchor="middle" dominant-baseline="central">+</text>
        </g>
      </g>

      
      <g id="lblShells" class="label-box">
        <path class="pointer-line" d="M 140 28 L 175 28 L 195 65" />
        <circle cx="195" cy="65" r="3" class="pointer-dot" />
        <text x="135" y="24" class="label-title" text-anchor="end">Electron Shells</text>
        <text x="135" y="39" class="label-sub" text-anchor="end">Electrons (−)</text>
      </g>

      
      <g id="lblNucleus" class="label-box">
        <path class="pointer-line" d="M 260 372 L 225 372 L 205 235" />
        <circle cx="205" cy="235" r="3" class="pointer-dot" />
        <text x="265" y="368" class="label-title" text-anchor="start">Nucleus</text>
        <text x="265" y="383" class="label-sub" text-anchor="start">Protons (+) &amp; Neutrons (0)</text>
      </g>
    </svg>
  </div>

  
  <div class="ctrl-bar" role="toolbar" aria-label="Atom component filters">
    <button class="btn active" data-filter="all">All</button>
    <button class="btn" data-filter="proton"><span class="dot dot-p"></span>Protons (+)</button>
    <button class="btn" data-filter="neutron"><span class="dot dot-n"></span>Neutrons (0)</button>
    <button class="btn" data-filter="electron"><span class="dot dot-e"></span>Electrons (−)</button>
  </div>

  <script>
    const buttons = document.querySelectorAll('.btn');
    const protons = document.querySelectorAll('.proton');
    const neutrons = document.querySelectorAll('.neutron');
    const electrons = document.querySelectorAll('.electron');
    const orbits = document.querySelectorAll('.orbit');

    function setFilter(type) {
      buttons.forEach(b => b.classList.toggle('active', b.dataset.filter === type));

      const setVisibility = (list, isDim) => {
        list.forEach(el => {
          el.classList.toggle('dimmed', isDim);
          el.classList.toggle('highlighted', !isDim && type !== 'all');
        });
      };

      if (type === 'all') {
        setVisibility(protons, false);
        setVisibility(neutrons, false);
        setVisibility(electrons, false);
        orbits.forEach(o => o.classList.remove('active'));
      } else if (type === 'proton') {
        setVisibility(protons, false);
        setVisibility(neutrons, true);
        setVisibility(electrons, true);
        orbits.forEach(o => o.classList.remove('active'));
      } else if (type === 'neutron') {
        setVisibility(protons, true);
        setVisibility(neutrons, false);
        setVisibility(electrons, true);
        orbits.forEach(o => o.classList.remove('active'));
      } else if (type === 'electron') {
        setVisibility(protons, true);
        setVisibility(neutrons, true);
        setVisibility(electrons, false);
        orbits.forEach(o => o.classList.add('active'));
      }
    }

    buttons.forEach(btn => {
      btn.addEventListener('click', () => setFilter(btn.dataset.filter));
    });
  </script>
</body>
</html>

OGS.7.PS.4

Aligned learning resources

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