<!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;
      user-select: none;
    }

    .controls {
      display: flex;
      gap: 6px;
      margin-bottom: 8px;
      width: 100%;
      max-width: 480px;
      justify-content: center;
    }

    .tab-btn {
      flex: 1;
      padding: 6px 10px;
      font-size: 13px;
      font-weight: 600;
      border: 1px solid #cbd5e1;
      border-radius: 8px;
      background: #f8fafc;
      color: #475569;
      cursor: pointer;
      text-align: center;
      transition: all 0.2s ease;
    }

    .tab-btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
      box-shadow: 0 2px 4px rgba(2, 132, 199, 0.25);
    }

    .diagram-stage {
      position: relative;
      width: 100%;
      max-width: 440px;
      aspect-ratio: 1.1 / 1;
      margin: auto 0;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    /* Outer Circle: Bases */
    .circle-bases {
      position: absolute;
      inset: 2%;
      background: #f1f5f9;
      border: 2px solid #94a3b8;
      border-radius: 50%;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding-top: 14px;
      transition: opacity 0.3s ease, border-color 0.3s ease, background-color 0.3s ease;
    }

    .bases-header {
      text-align: center;
      line-height: 1.2;
    }

    .bases-title {
      font-size: 15px;
      font-weight: 700;
      color: #334155;
      letter-spacing: -0.2px;
    }

    .bases-subtitle {
      font-size: 12px;
      color: #64748b;
      font-weight: 500;
    }

    /* Insoluble examples placed in upper region of Bases circle */
    .insoluble-group {
      display: flex;
      flex-wrap: wrap;
      justify-content: center;
      gap: 6px;
      margin-top: 10px;
      padding: 0 16px;
      z-index: 2;
      transition: opacity 0.3s ease;
    }

    .chip {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 3px 8px;
      font-size: 12px;
      font-weight: 600;
      color: #334155;
      white-space: nowrap;
      box-shadow: 0 1px 2px rgba(0,0,0,0.04);
    }

    .chip sub {
      font-size: 9px;
      vertical-align: sub;
    }

    .chip .tag {
      font-size: 10px;
      color: #64748b;
      font-weight: 500;
      margin-left: 2px;
    }

    /* Inner Nested Circle: Alkalis */
    .circle-alkalis {
      position: absolute;
      bottom: 12px;
      width: 78%;
      height: 56%;
      background: #e0f2fe;
      border: 2px solid #0284c7;
      border-radius: 50%;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 8px 12px 14px 12px;
      z-index: 3;
      transition: all 0.3s ease;
    }

    .alkalis-title {
      font-size: 14px;
      font-weight: 700;
      color: #0369a1;
      line-height: 1.2;
    }

    .alkalis-subtitle {
      font-size: 11px;
      color: #0284c7;
      font-weight: 600;
      margin-bottom: 6px;
    }

    .soluble-group {
      display: flex;
      flex-wrap: wrap;
      justify-content: center;
      gap: 5px;
    }

    .chip-alkali {
      background: #ffffff;
      border: 1px solid #7dd3fc;
      color: #0369a1;
      border-radius: 6px;
      padding: 3px 7px;
      font-size: 11px;
      font-weight: 600;
      box-shadow: 0 1px 2px rgba(2, 132, 199, 0.1);
    }

    .chip-alkali sub {
      font-size: 9px;
      vertical-align: sub;
    }

    /* Dimming styles based on active filter */
    .stage-alkalis-only .insoluble-group,
    .stage-alkalis-only .bases-header {
      opacity: 0.25;
    }

    .stage-insoluble-only .circle-alkalis {
      opacity: 0.2;
    }

    /* Caption footer */
    .caption-box {
      margin-top: 8px;
      padding: 8px 14px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      text-align: center;
      width: 100%;
      max-width: 480px;
    }

    .caption-text {
      font-size: 13px;
      font-weight: 700;
      color: #0f172a;
    }

    .caption-sub {
      font-size: 11px;
      color: #64748b;
      margin-top: 2px;
    }
  </style>
</head>
<body>

  <div class="controls">
    <button class="tab-btn active" data-mode="all" onclick="setMode('all')">All Bases</button>
    <button class="tab-btn" data-mode="insoluble" onclick="setMode('insoluble')">Insoluble Bases</button>
    <button class="tab-btn" data-mode="alkalis" onclick="setMode('alkalis')">Alkalis (Soluble)</button>
  </div>

  <div id="stage" class="diagram-stage">
    
    <div class="circle-bases">
      <div class="bases-header">
        <div class="bases-title">Bases</div>
        <div class="bases-subtitle">Neutralise acids</div>
      </div>

      
      <div class="insoluble-group">
        <div class="chip">CuO <span class="tag">(solid)</span></div>
        <div class="chip">Fe<sub>2</sub>O<sub>3</sub> <span class="tag">(solid)</span></div>
        <div class="chip">CaCO<sub>3</sub> <span class="tag">(solid)</span></div>
      </div>

      
      <div class="circle-alkalis">
        <div class="alkalis-title">Alkalis</div>
        <div class="alkalis-subtitle">Soluble bases (form OH⁻)</div>
        <div class="soluble-group">
          <div class="chip-alkali">NaOH <span style="font-size:10px; opacity:0.8;">(aq)</span></div>
          <div class="chip-alkali">KOH <span style="font-size:10px; opacity:0.8;">(aq)</span></div>
          <div class="chip-alkali">Ca(OH)<sub>2</sub> <span style="font-size:10px; opacity:0.8;">(aq)</span></div>
        </div>
      </div>
    </div>
  </div>

  <div class="caption-box">
    <div class="caption-text">All alkalis are bases, but not all bases are alkalis.</div>
    <div id="subtext" class="caption-sub">An alkali is simply a base that dissolves in water.</div>
  </div>

  <script>
    function setMode(mode) {
      const stage = document.getElementById('stage');
      const subtext = document.getElementById('subtext');
      const buttons = document.querySelectorAll('.tab-btn');

      buttons.forEach(btn => {
        btn.classList.toggle('active', btn.getAttribute('data-mode') === mode);
      });

      stage.className = 'diagram-stage';

      if (mode === 'insoluble') {
        stage.classList.add('stage-insoluble-only');
        subtext.textContent = 'Insoluble metal oxides & carbonates do not dissolve in water.';
      } else if (mode === 'alkalis') {
        stage.classList.add('stage-alkalis-only');
        subtext.textContent = 'Alkalis dissolve in water to release hydroxide ions (OH⁻).';
      } else {
        subtext.textContent = 'An alkali is simply a base that dissolves in water.';
      }
    }
  </script>
</body>
</html>

Defining Acids, Bases, and Soluble Alkalis

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Insoluble Base vs Soluble Alkali</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: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }

    .main-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 20px;
      width: 100%;
      max-width: 520px;
    }

    /* Stack vertically on narrow mobile screens to avoid cramped containers */
    @media (max-width: 420px) {
      .main-grid {
        grid-template-columns: 1fr;
        gap: 16px;
        max-width: 260px;
      }
    }

    .beaker-card {
      display: flex;
      flex-direction: column;
      align-items: center;
      background: transparent;
      padding: 4px;
    }

    .formula-tag {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      margin-bottom: 6px;
      text-align: center;
    }

    .beaker-container {
      position: relative;
      width: 100%;
      max-width: 155px;
      height: 150px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    svg.beaker-svg {
      width: 100%;
      height: 100%;
      overflow: visible;
    }

    .status-badge {
      margin-top: 8px;
      text-align: center;
      line-height: 1.35;
    }

    .badge-title {
      font-size: 14px;
      font-weight: 700;
      display: block;
    }

    .badge-sub {
      font-size: 12px;
      font-weight: 600;
      display: inline-block;
      margin-top: 2px;
      padding: 2px 8px;
      border-radius: 6px;
    }

    .insoluble-title {
      color: #334155;
    }
    .insoluble-sub {
      color: #475569;
      background: #f1f5f9;
    }

    .alkali-title {
      color: #6b21a8;
    }
    .alkali-sub {
      color: #6b21a8;
      background: #f3e8ff;
    }

    .ion-label {
      font-size: 11px;
      font-weight: 700;
      font-family: system-ui, sans-serif;
    }
  </style>
</head>
<body>

  <div class="main-grid">
    
    <div class="beaker-card">
      <div class="formula-tag">CuO (Copper oxide)</div>
      <div class="beaker-container">
        <svg class="beaker-svg" viewBox="0 0 160 160">
          
          <path d="M 22 25 L 30 25 L 30 142 Q 30 152 42 152 L 118 152 Q 130 152 130 142 L 130 25 L 138 25" 
                fill="none" stroke="#94a3b8" stroke-width="3" stroke-linecap="round"/>
          
          
          <path d="M 33 65 Q 80 63 127 65 L 127 140 Q 127 149 118 149 L 42 149 Q 33 149 33 140 Z" 
                fill="#e0f2fe" opacity="0.85"/>
          <path d="M 33 65 Q 80 62 127 65" fill="none" stroke="#bae6fd" stroke-width="2"/>

          
          <text x="80" y="94" text-anchor="middle" fill="#0284c7" font-size="11.5" font-weight="600">Water</text>

          
          <path d="M 40 148 C 52 136, 70 134, 80 136 C 90 134, 108 136, 120 148 Z" fill="#1e293b"/>
          <circle cx="54" cy="143" r="2.5" fill="#0f172a"/>
          <circle cx="68" cy="140" r="2.5" fill="#334155"/>
          <circle cx="82" cy="139" r="3" fill="#0f172a"/>
          <circle cx="96" cy="141" r="2.5" fill="#334155"/>
          <circle cx="106" cy="144" r="2.5" fill="#0f172a"/>

          
          <rect x="34" y="112" width="92" height="18" rx="4" fill="#ffffff" stroke="#cbd5e1" stroke-width="1"/>
          <text x="80" y="125" text-anchor="middle" fill="#334155" font-size="9.5" font-weight="700">Solid stays undissolved</text>
        </svg>
      </div>
      <div class="status-badge">
        <span class="badge-title insoluble-title">Insoluble Base</span>
        <span class="badge-sub insoluble-sub">Not an Alkali</span>
      </div>
    </div>

    
    <div class="beaker-card">
      <div class="formula-tag">NaOH (Sodium hydroxide)</div>
      <div class="beaker-container">
        <svg class="beaker-svg" viewBox="0 0 160 160">
          
          <path d="M 22 25 L 30 25 L 30 142 Q 30 152 42 152 L 118 152 Q 130 152 130 142 L 130 25 L 138 25" 
                fill="none" stroke="#94a3b8" stroke-width="3" stroke-linecap="round"/>
          
          
          <path d="M 33 65 Q 80 63 127 65 L 127 140 Q 127 149 118 149 L 42 149 Q 33 149 33 140 Z" 
                fill="#d8b4fe" opacity="0.6"/>
          <path d="M 33 65 Q 80 62 127 65" fill="none" stroke="#a855f7" stroke-width="2"/>

          
          <g transform="translate(80, 77)">
            <rect x="-57" y="-9" width="114" height="18" rx="9" fill="#ffffff" stroke="#9333ea" stroke-width="1.2"/>
            <text x="0" y="3.5" text-anchor="middle" fill="#581c87" font-size="9.5" font-weight="700">Turns Purple (pH 14)</text>
          </g>

          
          
          <g transform="translate(56, 105)">
            <circle cx="0" cy="0" r="12" fill="#7c3aed"/>
            <text x="0" y="4" text-anchor="middle" fill="#ffffff" class="ion-label">OH⁻</text>
          </g>

          
          <g transform="translate(104, 105)">
            <circle cx="0" cy="0" r="11" fill="#2563eb"/>
            <text x="0" y="4" text-anchor="middle" fill="#ffffff" class="ion-label">Na⁺</text>
          </g>

          
          <g transform="translate(58, 134)">
            <circle cx="0" cy="0" r="11" fill="#2563eb"/>
            <text x="0" y="4" text-anchor="middle" fill="#ffffff" class="ion-label">Na⁺</text>
          </g>

          
          <g transform="translate(102, 134)">
            <circle cx="0" cy="0" r="12" fill="#7c3aed"/>
            <text x="0" y="4" text-anchor="middle" fill="#ffffff" class="ion-label">OH⁻</text>
          </g>
        </svg>
      </div>
      <div class="status-badge">
        <span class="badge-title alkali-title">Soluble Base = Alkali</span>
        <span class="badge-sub alkali-sub">Releases OH⁻ ions</span>
      </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">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      background: #ffffff;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      gap: 12px;
      min-height: 100vh;
      user-select: none;
    }

    .container {
      width: 100%;
      max-width: 480px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .header-row {
      width: 100%;
      display: flex;
      justify-content: space-between;
      align-items: center;
      gap: 8px;
    }

    .controls {
      display: flex;
      gap: 4px;
      background: #f1f5f9;
      padding: 3px;
      border-radius: 8px;
    }

    .btn-step {
      border: none;
      background: transparent;
      color: #64748b;
      font-size: 12px;
      font-weight: 600;
      padding: 5px 9px;
      border-radius: 6px;
      cursor: pointer;
      transition: all 0.2s ease;
    }

    .btn-step.active {
      background: #ffffff;
      color: #1e2945;
      box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }

    .btn-play {
      border: 1px solid #e2e8f0;
      background: #ffffff;
      color: #1e2945;
      width: 28px;
      height: 28px;
      border-radius: 6px;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 12px;
    }

    /* Stage Area */
    .stage {
      position: relative;
      width: 100%;
      height: 180px;
      display: flex;
      justify-content: space-between;
      align-items: flex-end;
      padding: 30px 10px 10px 10px;
      overflow: visible;
    }

    /* Beakers */
    .beaker-wrapper {
      position: relative;
      width: 72px;
      height: 95px;
      z-index: 5;
      transition: transform 0.5s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.4s ease;
    }

    .beaker-label {
      position: absolute;
      top: -24px;
      left: 50%;
      transform: translateX(-50%);
      font-size: 12px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      white-space: nowrap;
      z-index: 10;
    }

    .label-base { color: #b45309; }
    .label-acid { color: #e11d48; }

    .beaker {
      width: 100%;
      height: 100%;
      border: 2px solid #94a3b8;
      border-top: none;
      border-radius: 0 0 10px 10px;
      background: rgba(248, 250, 252, 0.85);
      display: flex;
      flex-direction: column;
      justify-content: flex-end;
      position: relative;
      overflow: hidden;
    }

    .liquid-base {
      width: 100%;
      height: 58px;
      background: rgba(254, 240, 138, 0.6);
      border-radius: 0 0 8px 8px;
      display: flex;
      flex-wrap: wrap;
      align-content: center;
      justify-content: center;
      gap: 3px;
      padding: 3px;
      transition: height 0.4s ease;
    }

    .liquid-acid {
      width: 100%;
      height: 58px;
      background: rgba(254, 205, 211, 0.6);
      border-radius: 0 0 8px 8px;
      display: flex;
      flex-wrap: wrap;
      align-content: center;
      justify-content: center;
      gap: 3px;
      padding: 3px;
      transition: height 0.4s ease;
    }

    /* Reaction Chamber */
    .chamber-wrapper {
      position: relative;
      width: 125px;
      height: 125px;
      z-index: 2;
    }

    .chamber-label {
      position: absolute;
      top: -24px;
      left: 50%;
      transform: translateX(-50%);
      font-size: 11px;
      font-weight: 700;
      color: #64748b;
      white-space: nowrap;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }

    .chamber {
      width: 100%;
      height: 100%;
      border: 2px dashed #cbd5e1;
      border-top: none;
      border-radius: 0 0 16px 16px;
      display: flex;
      flex-direction: column;
      justify-content: flex-end;
      background: #f8fafc;
      transition: border 0.3s ease;
      overflow: hidden;
    }

    .chamber-liquid {
      width: 100%;
      height: 0;
      background: #e0f2fe;
      border-radius: 0 0 14px 14px;
      transition: height 0.5s ease, background-color 0.4s ease;
      display: flex;
      flex-wrap: wrap;
      align-content: center;
      justify-content: center;
      gap: 4px;
      padding: 4px;
      overflow: hidden;
    }

    /* Particle Tags */
    .particle {
      font-size: 10px;
      font-weight: 700;
      padding: 2px 5px;
      border-radius: 10px;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      box-shadow: 0 1px 2px rgba(0,0,0,0.06);
      white-space: nowrap;
    }

    .p-cu { background: #fed7aa; color: #9a3412; }
    .p-o  { background: #fef08a; color: #854d0e; }
    .p-h  { background: #fecdd3; color: #be123c; }
    .p-cl { background: #bbf7d0; color: #15803d; }
    .p-h2o { background: #bae6fd; color: #0369a1; border: 1px solid #7dd3fc; }
    .p-salt { background: #e2e8f0; color: #334155; border: 1px solid #94a3b8; }

    /* Flow Streams */
    .stream {
      position: absolute;
      top: 36px;
      width: 4px;
      height: 48px;
      border-radius: 2px;
      opacity: 0;
      transition: opacity 0.3s ease;
      z-index: 4;
      pointer-events: none;
    }
    .stream-base {
      left: 88px;
      background: linear-gradient(to bottom, #fde047, #38bdf8);
      transform: rotate(35deg);
    }
    .stream-acid {
      right: 88px;
      background: linear-gradient(to bottom, #fda4af, #38bdf8);
      transform: rotate(-35deg);
    }

    /* Equations Section */
    .eq-box {
      width: 100%;
      background: #f8fafc;
      border: 1px solid #e6e6e6;
      border-radius: 10px;
      padding: 10px 12px;
      display: flex;
      flex-direction: column;
      gap: 6px;
    }

    .eq-row {
      display: flex;
      align-items: center;
      justify-content: space-between;
      font-size: 13px;
      font-weight: 600;
      color: #1e2945;
    }

    .eq-item {
      padding: 3px 8px;
      border-radius: 6px;
      transition: all 0.3s ease;
      text-align: center;
    }

    .eq-arrow {
      color: #94a3b8;
      font-weight: 700;
      padding: 0 4px;
    }

    .eq-chem {
      font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
      font-size: 12.5px;
      color: #475569;
    }

    /* Step states */
    .step-1 .beaker-wrap-base { transform: translate(0, 0) rotate(0deg); opacity: 1; }
    .step-1 .beaker-wrap-acid { transform: translate(0, 0) rotate(0deg); opacity: 1; }
    .step-1 .chamber-liquid { height: 0; }
    .step-1 .eq-reactants { background: rgba(34, 183, 255, 0.15); color: #0284c7; }

    .step-2 .beaker-wrap-base {
      transform: translate(32px, -38px) rotate(48deg);
      transform-origin: top right;
      opacity: 0.95;
    }
    .step-2 .beaker-wrap-acid {
      transform: translate(-32px, -38px) rotate(-48deg);
      transform-origin: top left;
      opacity: 0.95;
    }
    .step-2 .liquid-base { height: 20px; }
    .step-2 .liquid-acid { height: 20px; }
    .step-2 .stream { opacity: 0.85; }
    .step-2 .chamber { border: 2px dashed #22b7ff; }
    .step-2 .chamber-liquid { height: 55px; background: #e2e8f0; }
    .step-2 .eq-arrow { color: #22b7ff; }

    .step-3 .beaker-wrap-base { transform: translate(0, 0) rotate(0deg); opacity: 0.35; }
    .step-3 .beaker-wrap-acid { transform: translate(0, 0) rotate(0deg); opacity: 0.35; }
    .step-3 .liquid-base { height: 0; }
    .step-3 .liquid-acid { height: 0; }
    .step-3 .chamber { border: 2px solid #22b7ff; }
    .step-3 .chamber-liquid { height: 75px; background: #e0f2fe; }
    .step-3 .eq-products { background: rgba(34, 183, 255, 0.15); color: #0284c7; }

    @media (max-width: 380px) {
      .stage {
        padding: 26px 4px 6px 4px;
        height: 165px;
      }
      .beaker-wrapper {
        width: 62px;
        height: 85px;
      }
      .chamber-wrapper {
        width: 110px;
        height: 115px;
      }
      .btn-step {
        font-size: 11px;
        padding: 4px 6px;
      }
      .eq-row {
        font-size: 11.5px;
      }
      .eq-chem {
        font-size: 11px;
      }
      .particle {
        font-size: 9px;
        padding: 1px 4px;
      }
      .step-2 .beaker-wrap-base {
        transform: translate(24px, -32px) rotate(45deg);
      }
      .step-2 .beaker-wrap-acid {
        transform: translate(-24px, -32px) rotate(-45deg);
      }
      .stream-base { left: 74px; }
      .stream-acid { right: 74px; }
    }
  </style>
</head>
<body class="step-1">

  <div class="container">
    <div class="header-row">
      <div class="controls">
        <button class="btn-step active" id="step0">1. Reactants</button>
        <button class="btn-step" id="step1">2. Reacting</button>
        <button class="btn-step" id="step2">3. Products</button>
      </div>
      <button class="btn-play" id="playBtn" title="Play / Pause">⏸</button>
    </div>

    <div class="stage">
      
      <div class="beaker-wrapper beaker-wrap-base">
        <span class="beaker-label label-base">Base</span>
        <div class="beaker">
          <div class="liquid-base">
            <span class="particle p-cu">Cu²⁺</span>
            <span class="particle p-o">O²⁻</span>
          </div>
        </div>
      </div>

      <div class="stream stream-base"></div>

      
      <div class="chamber-wrapper">
        <span class="chamber-label">Reaction Chamber</span>
        <div class="chamber" id="chamber">
          <div class="chamber-liquid" id="chamberContent"></div>
        </div>
      </div>

      <div class="stream stream-acid"></div>

      
      <div class="beaker-wrapper beaker-wrap-acid">
        <span class="beaker-label label-acid">Acid</span>
        <div class="beaker">
          <div class="liquid-acid">
            <span class="particle p-h">H⁺</span>
            <span class="particle p-h">H⁺</span>
            <span class="particle p-cl">Cl⁻</span>
            <span class="particle p-cl">Cl⁻</span>
          </div>
        </div>
      </div>
    </div>

    
    <div class="eq-box">
      <div class="eq-row">
        <span class="eq-item eq-reactants">Base + Acid</span>
        <span class="eq-arrow">→</span>
        <span class="eq-item eq-products">Salt + Water</span>
      </div>
      <div class="eq-row eq-chem">
        <span class="eq-item eq-reactants">CuO + 2HCl</span>
        <span class="eq-arrow">→</span>
        <span class="eq-item eq-products">CuCl₂ + H₂O</span>
      </div>
    </div>
  </div>

  <script>
    const steps = ['step-1', 'step-2', 'step-3'];
    let currentStep = 0;
    let timer = null;
    let isPlaying = true;

    const btns = [
      document.getElementById('step0'),
      document.getElementById('step1'),
      document.getElementById('step2')
    ];
    const playBtn = document.getElementById('playBtn');
    const chamberContent = document.getElementById('chamberContent');

    function renderStage(idx) {
      document.body.className = steps[idx];
      btns.forEach((b, i) => b.classList.toggle('active', i === idx));

      if (idx === 0) {
        chamberContent.innerHTML = '';
      } else if (idx === 1) {
        chamberContent.innerHTML = `
          <span class="particle p-cu">Cu²⁺</span>
          <span class="particle p-o">O²⁻</span>
          <span class="particle p-h">H⁺</span>
          <span class="particle p-h">H⁺</span>
          <span class="particle p-cl">Cl⁻</span>
        `;
      } else {
        chamberContent.innerHTML = `
          <span class="particle p-salt">CuCl₂ (Salt)</span>
          <span class="particle p-h2o">H₂O (Water)</span>
        `;
      }
    }

    function setStep(idx) {
      currentStep = idx;
      renderStage(currentStep);
    }

    function nextStep() {
      currentStep = (currentStep + 1) % steps.length;
      renderStage(currentStep);
    }

    function startAuto() {
      isPlaying = true;
      playBtn.textContent = '⏸';
      clearInterval(timer);
      timer = setInterval(nextStep, 3200);
    }

    function stopAuto() {
      isPlaying = false;
      playBtn.textContent = '▶';
      clearInterval(timer);
    }

    btns.forEach((btn, i) => {
      btn.addEventListener('click', () => {
        stopAuto();
        setStep(i);
      });
    });

    playBtn.addEventListener('click', () => {
      if (isPlaying) {
        stopAuto();
      } else {
        nextStep();
        startAuto();
      }
    });

    // Initialize
    renderStage(0);
    startAuto();
  </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>Excess Soluble Alkali at Particulate Level</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 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      min-height: 100%;
      overflow-x: hidden;
    }

    /* Stepper Navigation */
    .tabs {
      display: flex;
      gap: 6px;
      width: 100%;
      max-width: 440px;
      margin-bottom: 8px;
    }
    .tab-btn {
      flex: 1;
      border: 1px solid #cbd5e1;
      background: #f8fafc;
      color: #475569;
      padding: 7px 4px;
      font-size: 12px;
      font-weight: 600;
      border-radius: 6px;
      cursor: pointer;
      text-align: center;
      transition: background 0.2s, color 0.2s, border-color 0.2s;
    }
    .tab-btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }

    /* Stage Area - No outer card border/shell */
    .stage-container {
      position: relative;
      width: 100%;
      max-width: 440px;
      height: 280px;
      background: transparent;
      overflow: hidden;
    }

    .step-panel {
      position: absolute;
      inset: 0;
      opacity: 0;
      pointer-events: none;
      transition: opacity 0.35s ease;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 6px 10px;
    }
    .step-panel.active {
      opacity: 1;
      pointer-events: auto;
    }

    /* Step 1: Solution & Excess Drop */
    .beaker-wrap {
      position: relative;
      display: flex;
      flex-direction: column;
      align-items: center;
      margin-top: 14px;
    }
    .drop-indicator {
      position: absolute;
      top: -30px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 2px;
      animation: drip 2.2s infinite ease-in;
    }
    .drop-shape {
      width: 12px;
      height: 12px;
      background: #fef08a;
      border: 1.5px solid #ca8a04;
      border-radius: 0 50% 50% 50%;
      transform: rotate(45deg);
    }
    .drop-text {
      font-size: 10px;
      font-weight: 700;
      color: #854d0e;
      white-space: nowrap;
    }

    @keyframes drip {
      0% { transform: translateY(0); opacity: 0; }
      25% { transform: translateY(0); opacity: 1; }
      60% { transform: translateY(28px); opacity: 0; }
      100% { transform: translateY(28px); opacity: 0; }
    }

    .beaker {
      position: relative;
      width: 170px;
      height: 130px;
      border: 3px solid #64748b;
      border-top: none;
      border-radius: 0 0 14px 14px;
      background: rgba(224, 242, 254, 0.45);
    }
    .beaker-lip {
      position: absolute;
      top: -3px;
      left: -8px;
      width: 186px;
      height: 3px;
      background: #64748b;
      border-radius: 2px;
    }

    .ion-grid {
      position: absolute;
      inset: 8px 6px 6px;
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      grid-template-rows: repeat(2, 1fr);
      gap: 5px;
      align-items: center;
      justify-items: center;
    }
    .ion {
      font-size: 12px;
      font-weight: 700;
      padding: 3px 5px;
      border-radius: 5px;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      line-height: 1;
    }
    .ion-na { background: #e0f2fe; color: #0369a1; border: 1px solid #bae6fd; }
    .ion-cl { background: #dcfce7; color: #15803d; border: 1px solid #bbf7d0; }
    .ion-h  { background: #ede9fe; color: #6d28d9; border: 1px solid #ddd6fe; }
    .ion-oh { background: #fee2e2; color: #b91c1c; border: 1px solid #fecaca; }
    .ion-excess {
      background: #fef08a;
      color: #854d0e;
      border: 1px solid #facc15;
    }

    /* Step 2: Heating & Evaporating */
    .dish-assembly {
      position: relative;
      display: flex;
      flex-direction: column;
      align-items: center;
      width: 180px;
      margin-top: 4px;
    }
    .steam-container {
      display: flex;
      gap: 16px;
      margin-bottom: 2px;
    }
    .steam {
      font-size: 12px;
      font-weight: 700;
      color: #64748b;
      animation: rise 2.2s infinite ease-out;
    }
    .steam:nth-child(2) { animation-delay: 0.7s; }
    .steam:nth-child(3) { animation-delay: 1.4s; }
    @keyframes rise {
      0% { transform: translateY(0); opacity: 0; }
      40% { opacity: 1; }
      100% { transform: translateY(-16px); opacity: 0; }
    }
    .evap-dish {
      width: 154px;
      height: 38px;
      background: #f1f5f9;
      border: 3px solid #64748b;
      border-top: none;
      border-radius: 0 0 100px 100px;
      position: relative;
      overflow: hidden;
    }
    .liquid-remaining {
      position: absolute;
      bottom: 0;
      left: 8px;
      right: 8px;
      height: 14px;
      background: #bae6fd;
      border-radius: 0 0 80px 80px;
    }
    .burner-gauze {
      width: 120px;
      height: 3px;
      background: #94a3b8;
      border-radius: 2px;
      margin-top: 5px;
    }
    .tripod {
      display: flex;
      justify-content: space-between;
      width: 100px;
      height: 32px;
    }
    .leg {
      width: 3px;
      height: 100%;
      background: #64748b;
      border-radius: 2px;
    }
    .flame {
      margin-top: -34px;
      font-size: 24px;
      animation: flicker 0.7s infinite alternate ease-in-out;
    }
    @keyframes flicker {
      0% { opacity: 0.85; }
      100% { opacity: 1; }
    }

    /* Step 3: Crystal Lattice */
    .magnifier-frame {
      width: 150px;
      height: 150px;
      border: 3px solid #64748b;
      border-radius: 50%;
      background: #f8fafc;
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      margin-top: 4px;
    }
    .crystal-lattice {
      display: grid;
      grid-template-columns: repeat(4, 22px);
      grid-template-rows: repeat(4, 22px);
      gap: 3px;
    }
    .c-unit {
      width: 22px;
      height: 22px;
      border-radius: 3px;
      font-size: 10px;
      font-weight: 700;
      display: flex;
      align-items: center;
      justify-content: center;
      line-height: 1;
    }
    .c-nacl {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      color: #334155;
    }
    .c-naoh {
      background: #fef08a;
      border: 1px solid #eab308;
      color: #854d0e;
    }

    /* Step Details & Badges */
    .step-badge {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      margin-top: 10px;
      text-align: center;
    }
    .step-subtext {
      font-size: 11px;
      color: #64748b;
      margin-top: 2px;
      text-align: center;
    }
    .alert-tag {
      background: #fee2e2;
      color: #b91c1c;
      border: 1px solid #fca5a5;
      padding: 4px 10px;
      border-radius: 6px;
      font-size: 12px;
      font-weight: 700;
      margin-top: 8px;
      text-align: center;
    }

    /* Controls */
    .controls {
      display: flex;
      align-items: center;
      gap: 8px;
      margin-top: 4px;
    }
    .ctrl-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 5px 12px;
      border-radius: 6px;
      font-size: 12px;
      font-weight: 600;
      cursor: pointer;
    }
    .ctrl-btn:hover {
      background: #e2e8f0;
    }
  </style>
</head>
<body>

  
  <div class="tabs">
    <button class="tab-btn active" id="tab0">1. Excess Alkali</button>
    <button class="tab-btn" id="tab1">2. Evaporation</button>
    <button class="tab-btn" id="tab2">3. Impure Crystals</button>
  </div>

  
  <div class="stage-container">

    
    <div class="step-panel active" id="panel0">
      <div class="beaker-wrap">
        <div class="drop-indicator">
          <div class="drop-shape"></div>
          <span class="drop-text">+1 drop NaOH</span>
        </div>
        <div class="beaker">
          <div class="beaker-lip"></div>
          <div class="ion-grid">
            <span class="ion ion-na">Na⁺</span>
            <span class="ion ion-cl">Cl⁻</span>
            <span class="ion ion-h">H⁺</span>
            <span class="ion ion-oh">OH⁻</span>
            <span class="ion ion-excess">Na⁺</span>
            <span class="ion ion-excess">OH⁻</span>
          </div>
        </div>
      </div>
      <div class="step-badge">Excess NaOH added beyond neutralization point</div>
      <div class="step-subtext">Extra Na⁺ and OH⁻ ions remain unreacted in solution</div>
    </div>

    
    <div class="step-panel" id="panel1">
      <div class="dish-assembly">
        <div class="steam-container">
          <span class="steam">↑ H₂O</span>
          <span class="steam">↑ H₂O</span>
          <span class="steam">↑ H₂O</span>
        </div>
        <div class="evap-dish">
          <div class="liquid-remaining"></div>
        </div>
        <div class="burner-gauze"></div>
        <div class="tripod">
          <div class="leg"></div>
          <div class="leg"></div>
        </div>
        <div class="flame">🔥</div>
      </div>
      <div class="step-badge">Water evaporates on heating</div>
      <div class="step-subtext">Only non-volatile solutes remain behind as liquid evaporates</div>
    </div>

    
    <div class="step-panel" id="panel2">
      <div class="magnifier-frame">
        <div class="crystal-lattice">
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-naoh">OH⁻</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-naoh">Na⁺</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-naoh">OH⁻</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-nacl">NaCl</div>
          <div class="c-unit c-naoh">Na⁺</div>
          <div class="c-unit c-nacl">NaCl</div>
        </div>
      </div>
      <div class="alert-tag">Impure, caustic salt crystals</div>
      <div class="step-subtext">NaCl lattice is contaminated with solid NaOH flakes</div>
    </div>

  </div>

  
  <div class="controls">
    <button class="ctrl-btn" id="prevBtn">◀ Prev</button>
    <button class="ctrl-btn" id="playBtn">⏸ Pause</button>
    <button class="ctrl-btn" id="nextBtn">Next ▶</button>
  </div>

  <script>
    let step = 0;
    let playing = true;
    let timer = null;
    const STEP_DURATION = 3500; // >= 500ms comfortable dwell time

    const panels = [
      document.getElementById('panel0'),
      document.getElementById('panel1'),
      document.getElementById('panel2')
    ];
    const tabs = [
      document.getElementById('tab0'),
      document.getElementById('tab1'),
      document.getElementById('tab2')
    ];
    const playBtn = document.getElementById('playBtn');
    const prevBtn = document.getElementById('prevBtn');
    const nextBtn = document.getElementById('nextBtn');

    function setStep(index) {
      step = (index + 3) % 3;
      panels.forEach((p, i) => p.classList.toggle('active', i === step));
      tabs.forEach((t, i) => t.classList.toggle('active', i === step));
    }

    function advance() {
      setStep(step + 1);
    }

    function startAutoPlay() {
      if (timer) clearInterval(timer);
      timer = setInterval(advance, STEP_DURATION);
      playing = true;
      playBtn.textContent = '⏸ Pause';
    }

    function stopAutoPlay() {
      if (timer) clearInterval(timer);
      playing = false;
      playBtn.textContent = '▶ Play';
    }

    tabs.forEach((tab, index) => {
      tab.addEventListener('click', () => {
        setStep(index);
        stopAutoPlay();
      });
    });

    prevBtn.addEventListener('click', () => {
      setStep(step - 1);
      stopAutoPlay();
    });

    nextBtn.addEventListener('click', () => {
      setStep(step + 1);
      stopAutoPlay();
    });

    playBtn.addEventListener('click', () => {
      if (playing) {
        stopAutoPlay();
      } else {
        advance();
        startAutoPlay();
      }
    });

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

Why Titration Is Required for Soluble Alkali Salt Preparations

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <title>Titration Apparatus</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: #ffffff;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 12px;
      user-select: none;
    }

    /* Controls Header */
    .controls {
      display: flex;
      gap: 8px;
      width: 100%;
      max-width: 420px;
      justify-content: center;
    }

    .toggle-btn {
      flex: 1;
      padding: 8px 12px;
      font-size: 13px;
      font-weight: 600;
      border-radius: 8px;
      border: 1.5px solid #e2e8f0;
      background: #f8fafc;
      color: #64748b;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: all 0.25s ease;
    }

    .toggle-btn.active {
      background: #22b7ff;
      border-color: #22b7ff;
      color: #ffffff;
      box-shadow: 0 2px 8px rgba(34, 183, 255, 0.25);
    }

    .indicator-pill {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      display: inline-block;
      border: 1px solid rgba(0,0,0,0.1);
    }
    .pill-pink { background: #ff2a85; }
    .pill-clear { background: #f1f5f9; border-color: #cbd5e1; }

    /* SVG Apparatus Diagram */
    .svg-container {
      width: 100%;
      max-width: 440px;
      height: auto;
      display: flex;
      justify-content: center;
      align-items: center;
      position: relative;
    }

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

    /* Liquid transitions */
    .flask-solution {
      transition: fill 0.5s ease, opacity 0.5s ease;
    }
    .burette-liquid {
      transition: height 0.6s ease, y 0.6s ease;
    }
    .status-badge {
      transition: all 0.4s ease;
    }

    /* Annotation styling */
    .label-line {
      stroke: #94a3b8;
      stroke-width: 1.2;
      stroke-dasharray: 2 2;
    }
    .label-text {
      font-size: 11.5px;
      fill: #475569;
      font-weight: 500;
    }
    .label-title {
      font-size: 12.5px;
      font-weight: 700;
      fill: #0f172a;
    }

    /* Droplet animation */
    @keyframes dropFall {
      0% { transform: translateY(0); opacity: 0; }
      30% { opacity: 1; }
      100% { transform: translateY(32px); opacity: 0; }
    }
    .falling-drop {
      animation: dropFall 1.8s cubic-bezier(0.4, 0, 0.6, 1) infinite;
    }
  </style>
</head>
<body>

  
  <div class="controls">
    <button id="btn1" class="toggle-btn active" onclick="setState(1)">
      <span class="indicator-pill pill-pink"></span>
      1. Excess Alkali
    </button>
    <button id="btn2" class="toggle-btn" onclick="setState(2)">
      <span class="indicator-pill pill-clear"></span>
      2. Exact End-point
    </button>
  </div>

  
  <div class="svg-container">
    <svg viewBox="0 0 420 400" xmlns="http://www.w3.org/2000/svg">
      <defs>
        
        <linearGradient id="pinkLiquid" x1="0%" y1="0%" x2="100%" y2="0%">
          <stop offset="0%" stop-color="#ff2d8d" stop-opacity="0.85"/>
          <stop offset="50%" stop-color="#ff479c" stop-opacity="0.9"/>
          <stop offset="100%" stop-color="#e61e7a" stop-opacity="0.85"/>
        </linearGradient>

        
        <linearGradient id="clearLiquid" x1="0%" y1="0%" x2="100%" y2="0%">
          <stop offset="0%" stop-color="#e2e8f0" stop-opacity="0.45"/>
          <stop offset="50%" stop-color="#f8fafc" stop-opacity="0.75"/>
          <stop offset="100%" stop-color="#cbd5e1" stop-opacity="0.5"/>
        </linearGradient>

        
        <linearGradient id="acidGrad" x1="0%" y1="0%" x2="100%" y2="0%">
          <stop offset="0%" stop-color="#e0f2fe" stop-opacity="0.7"/>
          <stop offset="50%" stop-color="#f0f9ff" stop-opacity="0.9"/>
          <stop offset="100%" stop-color="#bae6fd" stop-opacity="0.7"/>
        </linearGradient>

        
        <linearGradient id="glassShine" x1="0%" y1="0%" x2="100%" y2="0%">
          <stop offset="0%" stop-color="#ffffff" stop-opacity="0.6"/>
          <stop offset="30%" stop-color="#ffffff" stop-opacity="0.1"/>
          <stop offset="100%" stop-color="#ffffff" stop-opacity="0.4"/>
        </linearGradient>

        <clipPath id="flaskClip">
          <polygon points="196,245 224,245 258,348 162,348"/>
        </clipPath>
      </defs>

      
      <g id="clamp-stand">
        
        <rect x="75" y="360" width="130" height="12" rx="2" fill="#64748b"/>
        <rect x="75" y="360" width="130" height="3" fill="#94a3b8"/>
        
        <rect x="92" y="30" width="7" height="330" fill="#94a3b8"/>
        <rect x="92" y="30" width="2" height="330" fill="#cbd5e1"/>
        
        <rect x="88" y="105" width="15" height="18" rx="2" fill="#334155"/>
        
        <rect x="103" y="111" width="98" height="6" fill="#475569"/>
        
        <path d="M 201 106 C 205 106, 207 109, 207 114 C 207 119, 205 122, 201 122" fill="none" stroke="#334155" stroke-width="4"/>
        <path d="M 219 106 C 215 106, 213 109, 213 114 C 213 119, 215 122, 219 122" fill="none" stroke="#334155" stroke-width="4"/>
      </g>

      
      <g id="white-tile">
        <rect x="145" y="352" width="130" height="12" rx="2" fill="#ffffff" stroke="#cbd5e1" stroke-width="1.5"/>
        <rect x="146" y="353" width="128" height="3" fill="#f8fafc"/>
        <line x1="145" y1="364" x2="275" y2="364" stroke="#94a3b8" stroke-width="1"/>
      </g>

      
      <g id="conical-flask">
        
        <g clip-path="url(#flaskClip)">
          <path id="flaskLiquid" class="flask-solution" d="M 150 285 Q 210 282 270 285 L 270 355 L 150 355 Z" fill="url(#pinkLiquid)"/>
          
          <ellipse id="liquidSurface" cx="210" cy="285" rx="34" ry="4" fill="#ff479c" opacity="0.6"/>
        </g>

        
        <path d="M 202,230 L 202,246 L 164,348 Q 162,352 168,352 L 252,352 Q 258,352 256,348 L 218,246 L 218,230 Z" 
              fill="url(#glassShine)" stroke="#38bdf8" stroke-width="1.75" stroke-linejoin="round" opacity="0.85"/>
        
        
        <ellipse cx="210" cy="230" rx="8" ry="2.5" fill="none" stroke="#38bdf8" stroke-width="1.75"/>
        
        
        <line x1="184" y1="295" x2="198" y2="295" stroke="#94a3b8" stroke-width="1"/>
        <text x="180" y="297" font-size="7.5" fill="#64748b" text-anchor="end" font-weight="600">25 cm³</text>
      </g>

      
      <g id="burette">
        
        <rect x="203" y="32" width="14" height="168" fill="#f8fafc" stroke="#38bdf8" stroke-width="1.5"/>
        
        
        <rect id="acidLevel" class="burette-liquid" x="204.5" y="45" width="11" height="154" fill="url(#acidGrad)"/>
        
        
        <path id="meniscus" d="M 204.5 45 Q 210 47 215.5 45" stroke="#0284c7" stroke-width="1.5" fill="none"/>

        
        
        <line x1="203" y1="45" x2="209" y2="45" stroke="#0284c7" stroke-width="1"/>
        <text x="200" y="47" font-size="7.5" fill="#0369a1" text-anchor="end" font-weight="600">0</text>
        
        <line x1="203" y1="65" x2="207" y2="65" stroke="#0284c7" stroke-width="0.75"/>
        <line x1="203" y1="85" x2="207" y2="85" stroke="#0284c7" stroke-width="0.75"/>
        
        
        <line x1="203" y1="105" x2="209" y2="105" stroke="#0284c7" stroke-width="1"/>
        <text x="200" y="107" font-size="7.5" fill="#0369a1" text-anchor="end" font-weight="600">25</text>
        
        <line x1="203" y1="125" x2="207" y2="125" stroke="#0284c7" stroke-width="0.75"/>
        <line x1="203" y1="145" x2="207" y2="145" stroke="#0284c7" stroke-width="0.75"/>
        <line x1="203" y1="165" x2="207" y2="165" stroke="#0284c7" stroke-width="0.75"/>
        
        
        <line x1="203" y1="185" x2="209" y2="185" stroke="#0284c7" stroke-width="1"/>
        <text x="200" y="187" font-size="7.5" fill="#0369a1" text-anchor="end" font-weight="600">50</text>

        
        <path d="M 207,200 L 207,207 L 204,213 L 216,213 L 213,207 L 213,200 Z" fill="#94a3b8" stroke="#334155" stroke-width="1"/>
        <rect id="tapHandle" x="212" y="205" width="10" height="4" rx="1.5" fill="#0284c7" stroke="#0369a1" stroke-width="0.75"/>
        
        
        <path d="M 208.5,213 L 208.5,225 L 211.5,225 L 211.5,213 Z" fill="#f0f9ff" stroke="#38bdf8" stroke-width="1"/>

        
        <circle id="droplet" class="falling-drop" cx="210" cy="230" r="2.2" fill="#38bdf8"/>
      </g>

      
      
      <g>
        <line x1="217" y1="75" x2="280" y2="75" class="label-line"/>
        <text x="285" y="72" class="label-title">Burette</text>
        <text x="285" y="86" class="label-text">Measures acid titre</text>
      </g>

      
      <g>
        <line x1="240" y1="305" x2="295" y2="305" class="label-line"/>
        <text x="300" y="302" class="label-title">Conical Flask</text>
        <text x="300" y="316" class="label-text">Alkali + indicator</text>
      </g>

      
      <g>
        <line x1="275" y1="358" x2="310" y2="358" class="label-line"/>
        <text x="315" y="355" class="label-title">White Tile</text>
        <text x="315" y="369" class="label-text">Spots colour change</text>
      </g>

      
      <g id="statusBox" transform="translate(18, 140)">
        <rect id="badgeBg" width="128" height="64" rx="8" fill="#fdf2f8" stroke="#fbcfe8" stroke-width="1.5"/>
        <text id="badgeTitle" x="64" y="24" text-anchor="middle" font-size="12" font-weight="700" fill="#be185d">pH &gt; 8.2 (Alkali)</text>
        <text id="badgeDesc" x="64" y="44" text-anchor="middle" font-size="10.5" font-weight="600" fill="#9d174d">Pink solution</text>
      </g>
    </svg>
  </div>

  <script>
    function setState(step) {
      const btn1 = document.getElementById('btn1');
      const btn2 = document.getElementById('btn2');
      const flaskLiquid = document.getElementById('flaskLiquid');
      const liquidSurface = document.getElementById('liquidSurface');
      const acidLevel = document.getElementById('acidLevel');
      const meniscus = document.getElementById('meniscus');
      const badgeBg = document.getElementById('badgeBg');
      const badgeTitle = document.getElementById('badgeTitle');
      const badgeDesc = document.getElementById('badgeDesc');
      const tapHandle = document.getElementById('tapHandle');

      if (step === 1) {
        btn1.classList.add('active');
        btn2.classList.remove('active');

        // Burette starting position (0 cm3 added)
        acidLevel.setAttribute('y', '45');
        acidLevel.setAttribute('height', '154');
        meniscus.setAttribute('d', 'M 204.5 45 Q 210 47 215.5 45');

        // Flask pink state
        flaskLiquid.setAttribute('fill', 'url(#pinkLiquid)');
        liquidSurface.setAttribute('fill', '#ff479c');
        liquidSurface.setAttribute('opacity', '0.6');

        // Badge
        badgeBg.setAttribute('fill', '#fdf2f8');
        badgeBg.setAttribute('stroke', '#fbcfe8');
        badgeTitle.setAttribute('fill', '#be185d');
        badgeTitle.textContent = 'pH > 8.2 (Alkali)';
        badgeDesc.setAttribute('fill', '#9d174d');
        badgeDesc.textContent = 'Pink solution';

        tapHandle.setAttribute('transform', 'rotate(0 217 207)');
      } else {
        btn2.classList.add('active');
        btn1.classList.remove('active');

        // Burette delivered titre (dropped to 25 cm3)
        acidLevel.setAttribute('y', '105');
        acidLevel.setAttribute('height', '94');
        meniscus.setAttribute('d', 'M 204.5 105 Q 210 107 215.5 105');

        // Flask neutral colorless state
        flaskLiquid.setAttribute('fill', 'url(#clearLiquid)');
        liquidSurface.setAttribute('fill', '#cbd5e1');
        liquidSurface.setAttribute('opacity', '0.35');

        // Badge
        badgeBg.setAttribute('fill', '#f0fdf4');
        badgeBg.setAttribute('stroke', '#bbf7d0');
        badgeTitle.setAttribute('fill', '#15803d');
        badgeTitle.textContent = 'pH 7 (End-Point)';
        badgeDesc.setAttribute('fill', '#166534');
        badgeDesc.textContent = 'Sharp: Colourless';

        tapHandle.setAttribute('transform', 'rotate(45 217 207)');
      }
    }
  </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: transparent;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }

    .workflow {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 12px;
      width: 100%;
      max-width: 660px;
    }

    @media (max-width: 480px) {
      .workflow {
        grid-template-columns: 1fr;
        gap: 10px;
      }
    }

    .step-card {
      background: #ffffff;
      border: 2px solid #e6e6e6;
      border-radius: 12px;
      padding: 12px 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      position: relative;
      cursor: pointer;
      transition: border-color 0.25s ease, box-shadow 0.25s ease;
    }

    .step-card.active {
      border-color: #22b7ff;
      box-shadow: 0 0 0 2px rgba(34, 183, 255, 0.25);
    }

    .step-card.step-3.active {
      border-color: #10b981;
      box-shadow: 0 0 0 2px rgba(16, 185, 129, 0.25);
    }

    .badge {
      width: 24px;
      height: 24px;
      border-radius: 50%;
      background: #1e2945;
      color: #ffffff;
      font-size: 13px;
      font-weight: 700;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-bottom: 6px;
    }

    .step-card.active .badge {
      background: #22b7ff;
    }

    .step-card.step-3.active .badge {
      background: #10b981;
    }

    .art-container {
      width: 100%;
      height: 110px;
      display: flex;
      align-items: center;
      justify-content: center;
      margin: 4px 0 8px;
    }

    .art-container svg {
      width: 100%;
      height: 100%;
      max-height: 105px;
    }

    .label-title {
      font-size: 14px;
      font-weight: 700;
      line-height: 1.2;
      margin-bottom: 3px;
    }

    .label-sub {
      font-size: 12px;
      font-weight: 600;
      color: #6b7280;
    }

    .crystal-tag {
      color: #10b981;
      font-weight: 700;
    }

    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 12px;
      margin-top: 14px;
    }

    .btn-ctrl {
      background: #ffffff;
      border: 1px solid #e6e6e6;
      border-radius: 20px;
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      color: #1e2945;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 6px;
      user-select: none;
    }

    .btn-ctrl:active {
      background: #f8f9fa;
    }

    .dot-track {
      display: flex;
      gap: 6px;
    }

    .dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: #e6e6e6;
      cursor: pointer;
      transition: background 0.25s ease;
    }

    .dot.active {
      background: #22b7ff;
    }

    .dot:nth-child(3).active {
      background: #10b981;
    }
  </style>
</head>
<body>

  <div class="workflow">
    
    <div class="step-card active" onclick="setStep(0)">
      <div class="badge">1</div>
      <div class="art-container">
        <svg viewBox="0 0 100 110">
          
          <line x1="28" y1="10" x2="28" y2="105" stroke="#94a3b8" stroke-width="2.5" stroke-linecap="round"/>
          <line x1="18" y1="105" x2="42" y2="105" stroke="#94a3b8" stroke-width="3" stroke-linecap="round"/>
          <rect x="26" y="24" width="22" height="4" fill="#64748b" rx="1"/>
          
          <rect x="42" y="6" width="10" height="60" fill="#f1f5f9" stroke="#1e2945" stroke-width="1.5" rx="1"/>
          
          <rect x="43" y="22" width="8" height="43" fill="#cbd5e1"/>
          <line x1="42" y1="62" x2="52" y2="62" stroke="#1e2945" stroke-width="1"/>
          
          <polygon points="44,66 50,66 48,72 46,72" fill="#1e2945"/>
          <circle cx="53" cy="67" r="2.5" fill="#ef4444"/>
          
          <circle cx="47" cy="77" r="1.5" fill="#60a5fa"/>
          
          <polygon points="38,82 56,82 68,103 26,103" fill="#f8fafc" stroke="#1e2945" stroke-width="1.5" stroke-linejoin="round"/>
          
          <polygon points="34,92 60,92 66,102 28,102" fill="#f43f5e" opacity="0.8"/>
        </svg>
      </div>
      <div class="label-title">Find Volume</div>
      <div class="label-sub">22.40 cm³ (Titre)</div>
    </div>

    
    <div class="step-card" onclick="setStep(1)">
      <div class="badge">2</div>
      <div class="art-container">
        <svg viewBox="0 0 100 110">
          
          <path d="M 30 35 L 30 96 A 6 6 0 0 0 36 102 L 64 102 A 6 6 0 0 0 70 96 L 70 35" fill="#f8fafc" stroke="#1e2945" stroke-width="1.8" stroke-linecap="round"/>
          <line x1="28" y1="35" x2="34" y2="35" stroke="#1e2945" stroke-width="1.5"/>
          
          <path d="M 31 62 Q 50 60 69 62 L 69 96 A 5 5 0 0 1 64 101 L 36 101 A 5 5 0 0 1 31 96 Z" fill="#e0f2fe"/>
          
          <rect x="22" y="10" width="56" height="18" fill="#1e2945" rx="4"/>
          <text x="50" y="22" fill="#ffffff" font-size="8.5" font-weight="700" text-anchor="middle" font-family="sans-serif">NO INDICATOR</text>
          
          <circle cx="50" cy="78" r="10" fill="#fee2e2" stroke="#ef4444" stroke-width="1.5"/>
          <line x1="43" y1="71" x2="57" y2="85" stroke="#ef4444" stroke-width="1.8"/>
        </svg>
      </div>
      <div class="label-title">Mix Clean</div>
      <div class="label-sub">Exact volumes only</div>
    </div>

    
    <div class="step-card step-3" onclick="setStep(2)">
      <div class="badge">3</div>
      <div class="art-container">
        <svg viewBox="0 0 100 110">
          
          <path d="M 42 22 Q 40 14 44 8" stroke="#94a3b8" stroke-width="1.5" fill="none" stroke-linecap="round"/>
          <path d="M 50 20 Q 53 12 49 6" stroke="#94a3b8" stroke-width="1.5" fill="none" stroke-linecap="round"/>
          <path d="M 58 22 Q 56 14 60 8" stroke="#94a3b8" stroke-width="1.5" fill="none" stroke-linecap="round"/>
          
          <path d="M 22 42 Q 50 72 78 42 Z" fill="#ffffff" stroke="#1e2945" stroke-width="1.8"/>
          
          <line x1="18" y1="62" x2="82" y2="62" stroke="#475569" stroke-width="2"/>
          <line x1="28" y1="62" x2="18" y2="104" stroke="#64748b" stroke-width="2.5" stroke-linecap="round"/>
          <line x1="72" y1="62" x2="82" y2="104" stroke="#64748b" stroke-width="2.5" stroke-linecap="round"/>
          
          <path d="M 50 78 Q 42 94 50 102 Q 58 94 50 78 Z" fill="#38bdf8"/>
          <path d="M 50 86 Q 46 96 50 102 Q 54 96 50 86 Z" fill="#facc15"/>
          
          <polygon points="50,47 54,51 50,55 46,51" fill="#10b981"/>
          <polygon points="41,50 44,53 41,56 38,53" fill="#ffffff" stroke="#10b981" stroke-width="1"/>
          <polygon points="59,50 62,53 59,56 56,53" fill="#ffffff" stroke="#10b981" stroke-width="1"/>
          
          <text x="68" y="32" fill="#10b981" font-size="12" font-weight="bold">✦</text>
          <text x="24" y="34" fill="#10b981" font-size="9" font-weight="bold">✦</text>
        </svg>
      </div>
      <div class="label-title">Crystallize</div>
      <div class="label-sub"><span class="crystal-tag">Pure NaCl</span></div>
    </div>
  </div>

  <div class="controls">
    <button class="btn-ctrl" id="playBtn" onclick="togglePlay()">
      <span id="playIcon">⏸</span> Auto
    </button>
    <div class="dot-track">
      <div class="dot active" onclick="setStep(0)"></div>
      <div class="dot" onclick="setStep(1)"></div>
      <div class="dot" onclick="setStep(2)"></div>
    </div>
  </div>

  <script>
    let currentStep = 0;
    let isPlaying = true;
    let timer = null;

    const cards = document.querySelectorAll('.step-card');
    const dots = document.querySelectorAll('.dot');
    const playIcon = document.getElementById('playIcon');

    function updateUI() {
      cards.forEach((card, idx) => {
        card.classList.toggle('active', idx === currentStep);
      });
      dots.forEach((dot, idx) => {
        dot.classList.toggle('active', idx === currentStep);
      });
    }

    function setStep(idx) {
      currentStep = idx;
      updateUI();
    }

    function nextStep() {
      currentStep = (currentStep + 1) % 3;
      updateUI();
    }

    function startAuto() {
      stopAuto();
      timer = setInterval(nextStep, 3200);
      isPlaying = true;
      playIcon.textContent = '⏸';
    }

    function stopAuto() {
      if (timer) clearInterval(timer);
      isPlaying = false;
      playIcon.textContent = '▶';
    }

    function togglePlay() {
      if (isPlaying) {
        stopAuto();
      } else {
        nextStep();
        startAuto();
      }
    }

    // Initialize auto play
    startAuto();
  </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>Filtration: Insoluble Base vs Soluble Alkali</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }
    body {
      background: #f8f9fa;
      color: #1e2945;
      padding: 8px 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      min-height: auto;
    }
    .comparison-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      width: 100%;
      max-width: 640px;
    }
    @media (max-width: 520px) {
      .comparison-grid {
        grid-template-columns: 1fr;
        gap: 10px;
      }
    }
    .panel {
      background: #ffffff;
      border: 1px solid #e6e6e6;
      border-radius: 10px;
      padding: 10px 8px 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      transition: border-color 0.35s ease, box-shadow 0.35s ease;
    }
    .panel-title {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      margin-bottom: 4px;
      display: flex;
      align-items: center;
      gap: 5px;
      text-align: center;
    }
    .status-badge {
      font-size: 10.5px;
      font-weight: 700;
      padding: 4px 8px;
      border-radius: 10px;
      margin-top: 6px;
      text-align: center;
      line-height: 1.25;
      transition: background 0.35s ease, color 0.35s ease;
    }
    .badge-success {
      background: #dcfce7;
      color: #166534;
      border: 1px solid #bbf7d0;
    }
    .badge-fail {
      background: #fee2e2;
      color: #991b1b;
      border: 1px solid #fecaca;
    }
    svg {
      width: 100%;
      max-width: 275px;
      height: auto;
      display: block;
      overflow: visible;
    }
    .btn-row {
      margin-top: 10px;
      display: flex;
      gap: 8px;
    }
    .btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 6px 14px;
      border-radius: 6px;
      font-size: 12px;
      font-weight: 600;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 6px;
      transition: background-color 0.35s ease, border-color 0.35s ease, color 0.35s ease;
    }
    .btn:hover {
      background-color: #f1f5f9;
      border-color: #94a3b8;
    }
    .btn:active {
      background-color: #e2e8f0;
    }

    /* Flow Animations - Slow, readable, flicker-free, each phase visible >= 500ms */
    .drop-flow {
      opacity: 0;
      transition: opacity 0.4s ease;
    }
    .filter-active .insoluble-drop {
      animation: dropFallInsoluble 4.2s cubic-bezier(0.4, 0, 0.2, 1) infinite;
    }
    .filter-active .soluble-drop {
      animation: dropFallSoluble 4.2s cubic-bezier(0.4, 0, 0.2, 1) infinite 1.2s;
    }
    .filter-active .soluble-ion-passing {
      animation: ionPass 4.5s ease-in-out infinite;
    }
    .filter-active .solid-particle {
      animation: gentleFloat 4s ease-in-out infinite alternate;
    }

    @keyframes dropFallInsoluble {
      0% {
        transform: translateY(0);
        opacity: 0;
      }
      15% {
        opacity: 0.95;
      }
      65% {
        transform: translateY(38px);
        opacity: 0.95;
      }
      80% {
        transform: translateY(42px);
        opacity: 0;
      }
      100% {
        transform: translateY(0);
        opacity: 0;
      }
    }

    @keyframes dropFallSoluble {
      0% {
        transform: translateY(0);
        opacity: 0;
      }
      15% {
        opacity: 0.9;
      }
      65% {
        transform: translateY(38px);
        opacity: 0.9;
      }
      80% {
        transform: translateY(42px);
        opacity: 0;
      }
      100% {
        transform: translateY(0);
        opacity: 0;
      }
    }

    @keyframes ionPass {
      0% {
        transform: translateY(0);
        opacity: 0;
      }
      15% {
        opacity: 1;
        transform: translateY(4px);
      }
      50% {
        transform: translateY(28px);
        opacity: 1;
      }
      75% {
        transform: translateY(54px);
        opacity: 0.9;
      }
      90% {
        transform: translateY(62px);
        opacity: 0;
      }
      100% {
        transform: translateY(0);
        opacity: 0;
      }
    }

    @keyframes gentleFloat {
      0% {
        transform: translate(0, 0);
      }
      50% {
        transform: translate(0.5px, -0.8px);
      }
      100% {
        transform: translate(-0.5px, 0.4px);
      }
    }
  </style>
</head>
<body>

  <div class="comparison-grid" id="diagramRoot">
    
    <div class="panel">
      <div class="panel-title">
        <span>Insoluble Base (e.g. CuO)</span>
      </div>

      <svg viewBox="0 0 250 200" aria-label="Filtration of copper oxide separating insoluble solid">
        
        <polygon points="45,45 145,45 105,105 105,135 85,135 85,105" fill="#f8fafc" stroke="#94a3b8" stroke-width="1.8" />
        
        
        <polygon points="53,50 137,50 95,102" fill="#ffffff" stroke="#cbd5e1" stroke-width="1.5" />
        
        
        <polygon points="60,62 130,62 95,100" fill="#38bdf8" opacity="0.6" />

        
        <g class="solid-particle">
          <circle cx="90" cy="88" r="4" fill="#0f172a" />
          <circle cx="100" cy="87" r="3.5" fill="#0f172a" />
          <circle cx="95" cy="81" r="4" fill="#0f172a" />
          <circle cx="86" cy="82" r="3" fill="#0f172a" />
          <circle cx="104" cy="80" r="3" fill="#0f172a" />
          <circle cx="94" cy="74" r="3.5" fill="#0f172a" />
        </g>
        
        
        <line x1="145" y1="78" x2="108" y2="78" stroke="#0f172a" stroke-width="1" stroke-dasharray="2,2" />
        <text x="150" y="75" font-size="10.5" font-weight="700" fill="#0f172a">Residue</text>
        <text x="150" y="87" font-size="9" fill="#64748b">Excess CuO solid</text>

        
        <path d="M78,126 L58,178 Q58,188 68,188 L122,188 Q132,188 132,178 L112,126 Z" fill="none" stroke="#94a3b8" stroke-width="1.8" />
        
        
        <path d="M63,168 L58,178 Q58,188 68,188 L122,188 Q132,188 132,178 L127,168 Z" fill="#38bdf8" opacity="0.75" />

        
        <g class="insoluble-drop drop-flow">
          <ellipse cx="95" cy="140" rx="2.5" ry="4" fill="#0284c7" />
        </g>

        
        <line x1="145" y1="172" x2="128" y2="172" stroke="#0284c7" stroke-width="1" stroke-dasharray="2,2" />
        <text x="150" y="169" font-size="10.5" font-weight="700" fill="#0284c7">Filtrate</text>
        <text x="150" y="181" font-size="9" fill="#64748b">Pure CuSO₄ solution</text>
      </svg>

      <span class="status-badge badge-success">✓ Excess solid trapped by filter</span>
    </div>

    
    <div class="panel">
      <div class="panel-title">
        <span>Soluble Alkali (e.g. NaOH)</span>
      </div>

      <svg viewBox="0 0 250 200" aria-label="Filtration of sodium hydroxide where dissolved ions pass through">
        
        <polygon points="45,45 145,45 105,105 105,135 85,135 85,105" fill="#f8fafc" stroke="#94a3b8" stroke-width="1.8" />
        
        
        <polygon points="53,50 137,50 95,102" fill="#ffffff" stroke="#cbd5e1" stroke-width="1.5" />
        
        
        <polygon points="60,62 130,62 95,100" fill="#e2e8f0" opacity="0.5" />

        
        <g class="soluble-ion-passing">
          
          <circle cx="88" cy="68" r="5" fill="#f59e0b" />
          <text x="88" y="70.5" font-size="6" font-weight="700" fill="#ffffff" text-anchor="middle">Na⁺</text>
          
          
          <circle cx="102" cy="74" r="5" fill="#8b5cf6" />
          <text x="102" y="76.5" font-size="5.5" font-weight="700" fill="#ffffff" text-anchor="middle">OH⁻</text>
        </g>

        
        <line x1="145" y1="78" x2="108" y2="78" stroke="#dc2626" stroke-width="1" stroke-dasharray="2,2" />
        <text x="150" y="75" font-size="10.5" font-weight="700" fill="#dc2626">No Residue</text>
        <text x="150" y="87" font-size="9" fill="#64748b">Ions pass pores</text>

        
        <path d="M78,126 L58,178 Q58,188 68,188 L122,188 Q132,188 132,178 L112,126 Z" fill="none" stroke="#94a3b8" stroke-width="1.8" />
        
        
        <path d="M63,168 L58,178 Q58,188 68,188 L122,188 Q132,188 132,178 L127,168 Z" fill="#e2e8f0" opacity="0.6" />

        
        <circle cx="80" cy="177" r="4.2" fill="#f59e0b" />
        <text x="80" y="179.5" font-size="5.5" font-weight="700" fill="#fff" text-anchor="middle">Na⁺</text>
        
        <circle cx="95" cy="175" r="4.2" fill="#8b5cf6" />
        <text x="95" y="177.5" font-size="5" font-weight="700" fill="#fff" text-anchor="middle">OH⁻</text>

        <circle cx="110" cy="178" r="4.2" fill="#0ea5e9" />
        <text x="110" y="180.5" font-size="5" font-weight="700" fill="#fff" text-anchor="middle">Cl⁻</text>

        
        <g class="soluble-drop drop-flow">
          <ellipse cx="95" cy="140" rx="2.5" ry="4" fill="#94a3b8" />
        </g>

        
        <line x1="145" y1="172" x2="128" y2="172" stroke="#dc2626" stroke-width="1" stroke-dasharray="2,2" />
        <text x="150" y="169" font-size="10.5" font-weight="700" fill="#dc2626">Still Mixed</text>
        <text x="150" y="181" font-size="9" fill="#64748b">Salt + Alkali</text>
      </svg>

      <span class="status-badge badge-fail">✗ Filtration cannot separate dissolved ions!</span>
    </div>
  </div>

  <div class="btn-row">
    <button class="btn" id="toggleFlowBtn" onclick="toggleAnimation()" aria-label="Toggle flow animation">
      <span id="btnIcon">⏸</span> Flow Animation
    </button>
  </div>

  <script>
    let isFlowing = true;
    const root = document.getElementById('diagramRoot');
    const btnIcon = document.getElementById('btnIcon');

    // Start with animation active
    root.classList.add('filter-active');

    function toggleAnimation() {
      isFlowing = !isFlowing;
      if (isFlowing) {
        root.classList.add('filter-active');
        btnIcon.textContent = '⏸';
      } else {
        root.classList.remove('filter-active');
        btnIcon.textContent = '▶';
      }
    }
  </script>
</body>
</html>

UK-GCSE-SCIENCE-CHEM-CC-03-04

Aligned learning resources

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