<!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%;
      height: 100%;
      background: #ffffff;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      padding: 10px;
      user-select: none;
    }

    /* Filter Controls */
    .controls {
      display: flex;
      gap: 8px;
      justify-content: center;
      width: 100%;
      max-width: 480px;
    }
    .btn-filter {
      flex: 1;
      padding: 8px 12px;
      font-size: 13px;
      font-weight: 600;
      border-radius: 8px;
      border: 1px solid #e2e8f0;
      background: #f8fafc;
      color: #64748b;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 4px;
      transition: background 0.2s ease, color 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease;
    }
    .btn-filter.active {
      background: #ffffff;
      color: #0f172a;
      border-color: #cbd5e1;
      box-shadow: 0 2px 4px rgba(0,0,0,0.06);
    }
    .btn-filter[data-type="heat"].active {
      color: #dc2626;
      border-color: #fca5a5;
      background: #fef2f2;
    }
    .btn-filter[data-type="cool"].active {
      color: #2563eb;
      border-color: #bfdbfe;
      background: #eff6ff;
    }

    /* SVG Canvas */
    .svg-container {
      width: 100%;
      max-width: 480px;
      flex-grow: 1;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }

    /* State Transition Arrows */
    .arrow-group {
      cursor: pointer;
      transition: opacity 0.25s ease;
    }
    .arrow-path {
      fill: none;
      stroke-width: 3.5;
      stroke-linecap: round;
      transition: stroke-width 0.2s ease, stroke 0.2s ease;
    }
    .heat-arrow .arrow-path {
      stroke: #ef4444;
    }
    .cool-arrow .arrow-path {
      stroke: #3b82f6;
    }
    .arrow-label {
      font-size: 12px;
      font-weight: 700;
      text-anchor: middle;
      dominant-baseline: central;
      paint-order: stroke;
      stroke: #ffffff;
      stroke-width: 4px;
      stroke-linejoin: round;
    }
    .heat-arrow .arrow-label {
      fill: #dc2626;
    }
    .cool-arrow .arrow-label {
      fill: #2563eb;
    }

    .arrow-group.dimmed {
      opacity: 0.15;
    }
    .arrow-group.highlighted .arrow-path {
      stroke-width: 5;
    }

    /* Nodes */
    .node-bg {
      fill: #ffffff;
      stroke: #cbd5e1;
      stroke-width: 2;
    }
    .node-title {
      font-size: 15px;
      font-weight: 800;
      fill: #0f172a;
      text-anchor: middle;
    }
    .particle-solid { fill: #6366f1; }
    .particle-liquid { fill: #0ea5e9; }
    .particle-gas { fill: #f59e0b; }

    /* Legend */
    .legend {
      display: flex;
      gap: 16px;
      justify-content: center;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
      padding-top: 4px;
    }
    .legend-item {
      display: flex;
      align-items: center;
      gap: 6px;
    }
    .legend-bar {
      width: 18px;
      height: 4px;
      border-radius: 2px;
    }
    .legend-bar.heat { background: #ef4444; }
    .legend-bar.cool { background: #3b82f6; }
  </style>
</head>
<body>

  
  <div class="controls">
    <button class="btn-filter active" data-type="all">All Changes</button>
    <button class="btn-filter" data-type="heat">🔥 Heating (+Energy)</button>
    <button class="btn-filter" data-type="cool">❄️ Cooling (−Energy)</button>
  </div>

  
  <div class="svg-container">
    <svg viewBox="0 0 500 420">
      <defs>
        
        <marker id="arrow-heat" markerWidth="8" markerHeight="8" refX="5" refY="3" orient="auto">
          <path d="M0,0 L0,6 L7,3 z" fill="#ef4444" />
        </marker>
        <marker id="arrow-cool" markerWidth="8" markerHeight="8" refX="5" refY="3" orient="auto">
          <path d="M0,0 L0,6 L7,3 z" fill="#3b82f6" />
        </marker>
      </defs>

      
      
      <g class="arrow-group heat-arrow" data-type="heat">
        <path class="arrow-path" d="M 175,340 C 215,325 285,325 325,340" marker-end="url(#arrow-heat)" />
        <text class="arrow-label" x="250" y="322">Melting</text>
      </g>

      
      <g class="arrow-group cool-arrow" data-type="cool">
        <path class="arrow-path" d="M 325,375 C 285,390 215,390 175,375" marker-end="url(#arrow-cool)" />
        <text class="arrow-label" x="250" y="394">Freezing</text>
      </g>

      
      <g class="arrow-group heat-arrow" data-type="heat">
        <path class="arrow-path" d="M 370,290 C 375,200 325,120 295,95" marker-end="url(#arrow-heat)" />
        <text class="arrow-label" x="382" y="195" transform="rotate(62, 382, 195)">Evaporating</text>
      </g>

      
      <g class="arrow-group cool-arrow" data-type="cool">
        <path class="arrow-path" d="M 270,90 C 290,140 330,230 335,290" marker-end="url(#arrow-cool)" />
        <text class="arrow-label" x="316" y="185" transform="rotate(62, 316, 185)">Condensing</text>
      </g>

      
      <g class="arrow-group cool-arrow" data-type="cool">
        <path class="arrow-path" d="M 205,95 C 175,120 125,200 130,290" marker-end="url(#arrow-cool)" />
        <text class="arrow-label" x="118" y="195" transform="rotate(-62, 118, 195)">Deposition</text>
      </g>

      
      <g class="arrow-group heat-arrow" data-type="heat">
        <path class="arrow-path" d="M 165,290 C 170,230 210,140 230,90" marker-end="url(#arrow-heat)" />
        <text class="arrow-label" x="184" y="185" transform="rotate(-62, 184, 185)">Sublimation</text>
      </g>

      

      
      <g transform="translate(250, 60)">
        <circle class="node-bg" cx="0" cy="0" r="48" />
        
        <circle class="particle-gas" cx="-24" cy="-18" r="5" />
        <circle class="particle-gas" cx="22" cy="-12" r="5" />
        <circle class="particle-gas" cx="-12" cy="18" r="5" />
        <circle class="particle-gas" cx="18" cy="20" r="5" />
        <circle class="particle-gas" cx="0" cy="-2" r="5" />
        <text class="node-title" x="0" y="-30">GAS</text>
      </g>

      
      <g transform="translate(115, 355)">
        <circle class="node-bg" cx="0" cy="0" r="48" />
        
        <g transform="translate(-16, -16)">
          <circle class="particle-solid" cx="0" cy="0" r="4.5" />
          <circle class="particle-solid" cx="16" cy="0" r="4.5" />
          <circle class="particle-solid" cx="32" cy="0" r="4.5" />
          <circle class="particle-solid" cx="0" cy="16" r="4.5" />
          <circle class="particle-solid" cx="16" cy="16" r="4.5" />
          <circle class="particle-solid" cx="32" cy="16" r="4.5" />
          <circle class="particle-solid" cx="0" cy="32" r="4.5" />
          <circle class="particle-solid" cx="16" cy="32" r="4.5" />
          <circle class="particle-solid" cx="32" cy="32" r="4.5" />
        </g>
        <text class="node-title" x="0" y="-30">SOLID</text>
      </g>

      
      <g transform="translate(385, 355)">
        <circle class="node-bg" cx="0" cy="0" r="48" />
        
        <circle class="particle-liquid" cx="-15" cy="-12" r="4.8" />
        <circle class="particle-liquid" cx="0" cy="-14" r="4.8" />
        <circle class="particle-liquid" cx="15" cy="-8" r="4.8" />
        <circle class="particle-liquid" cx="-20" cy="3" r="4.8" />
        <circle class="particle-liquid" cx="-6" cy="1" r="4.8" />
        <circle class="particle-liquid" cx="9" cy="6" r="4.8" />
        <circle class="particle-liquid" cx="22" cy="7" r="4.8" />
        <circle class="particle-liquid" cx="-12" cy="18" r="4.8" />
        <circle class="particle-liquid" cx="4" cy="20" r="4.8" />
        <text class="node-title" x="0" y="-30">LIQUID</text>
      </g>
    </svg>
  </div>

  
  <div class="legend">
    <div class="legend-item">
      <div class="legend-bar heat"></div>
      <span>Energy Absorbed (Heating)</span>
    </div>
    <div class="legend-item">
      <div class="legend-bar cool"></div>
      <span>Energy Released (Cooling)</span>
    </div>
  </div>

  <script>
    const buttons = document.querySelectorAll('.btn-filter');
    const arrowGroups = document.querySelectorAll('.arrow-group');

    function applyFilter(type) {
      buttons.forEach(b => b.classList.toggle('active', b.dataset.type === type));
      arrowGroups.forEach(arrow => {
        const arrowType = arrow.dataset.type;
        if (type === 'all') {
          arrow.classList.remove('dimmed');
          arrow.classList.remove('highlighted');
        } else if (arrowType === type) {
          arrow.classList.remove('dimmed');
          arrow.classList.add('highlighted');
        } else {
          arrow.classList.add('dimmed');
          arrow.classList.remove('highlighted');
        }
      });
    }

    buttons.forEach(btn => {
      btn.addEventListener('click', () => {
        applyFilter(btn.dataset.type);
      });
    });

    arrowGroups.forEach(arrow => {
      arrow.addEventListener('click', () => {
        applyFilter(arrow.dataset.type);
      });
    });
  </script>
</body>
</html>

Particle Models for Solids, Liquids, Gases and State Changes

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

    /* Controls Header */
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      margin-bottom: 12px;
      width: 100%;
      max-width: 500px;
    }

    .btn-step {
      flex: 1;
      padding: 8px 12px;
      font-size: 14px;
      font-weight: 600;
      border: 1px solid #cbd5e1;
      background: #f8fafc;
      color: #475569;
      border-radius: 8px;
      cursor: pointer;
      transition: all 0.25s ease;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
    }

    .btn-step.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
      box-shadow: 0 2px 4px rgba(37, 99, 235, 0.2);
    }

    /* Main Comparison Grid */
    .grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      width: 100%;
      max-width: 620px;
    }

    @media (max-width: 440px) {
      .grid {
        grid-template-columns: 1fr;
      }
    }

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

    .panel-title {
      font-size: 15px;
      font-weight: 700;
      margin-bottom: 4px;
      text-align: center;
    }

    .title-physical {
      color: #0284c7;
    }

    .title-chemical {
      color: #7c3aed;
    }

    .stage-box {
      width: 100%;
      height: 190px;
      position: relative;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      overflow: hidden;
      margin: 8px 0;
    }

    svg.stage-svg {
      width: 100%;
      height: 100%;
      display: block;
    }

    /* SVG Atom styling & animations */
    .atom-o {
      fill: #ef4444;
      stroke: #b91c1c;
      stroke-width: 1.5;
    }

    .atom-h {
      fill: #f1f5f9;
      stroke: #64748b;
      stroke-width: 1.5;
    }

    .bond-line {
      stroke: #94a3b8;
      stroke-width: 2.5;
      stroke-linecap: round;
      transition: all 0.7s cubic-bezier(0.4, 0, 0.2, 1);
    }

    .atom-text {
      font-size: 11px;
      font-weight: 700;
      text-anchor: middle;
      dominant-baseline: central;
      user-select: none;
      pointer-events: none;
    }

    .text-o {
      fill: #ffffff;
    }

    .text-h {
      fill: #334155;
    }

    .atom-group {
      transition: transform 0.7s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.4s ease;
    }

    /* Subtitle / summary badge */
    .badge {
      font-size: 12px;
      font-weight: 600;
      padding: 4px 8px;
      border-radius: 6px;
      text-align: center;
      line-height: 1.3;
      width: 100%;
    }

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

    .badge-chemical {
      background: #ede9fe;
      color: #6d28d9;
    }

    /* Legend */
    .legend {
      display: flex;
      justify-content: center;
      gap: 16px;
      margin-top: 10px;
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
    }

    .legend-item {
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .legend-dot {
      width: 14px;
      height: 14px;
      border-radius: 50%;
      display: inline-block;
    }

    .dot-o {
      background: #ef4444;
      border: 1px solid #b91c1c;
    }

    .dot-h {
      background: #f1f5f9;
      border: 1px solid #64748b;
    }
  </style>
</head>
<body>

  
  <div class="controls">
    <button class="btn-step active" id="btnBefore" onclick="setStep(0)">
      <span>1</span> Before (Solid / Reactants)
    </button>
    <button class="btn-step" id="btnAfter" onclick="setStep(1)">
      <span>2</span> After (Change)
    </button>
  </div>

  
  <div class="grid">
    
    
    <div class="panel">
      <div class="panel-title title-physical">Physical Change</div>
      
      <div class="stage-box">
        <svg class="stage-svg" viewBox="0 0 200 190">
          
          <g id="phys-m1" class="atom-group" transform="translate(60, 65)">
            <line x1="0" y1="0" x2="-14" y2="12" class="bond-line" />
            <line x1="0" y1="0" x2="14" y2="12" class="bond-line" />
            <circle cx="-14" cy="12" r="9" class="atom-h" />
            <text x="-14" y="12" class="atom-text text-h">H</text>
            <circle cx="14" cy="12" r="9" class="atom-h" />
            <text x="14" y="12" class="atom-text text-h">H</text>
            <circle cx="0" cy="0" r="14" class="atom-o" />
            <text x="0" y="0" class="atom-text text-o">O</text>
          </g>

          
          <g id="phys-m2" class="atom-group" transform="translate(140, 65)">
            <line x1="0" y1="0" x2="-14" y2="12" class="bond-line" />
            <line x1="0" y1="0" x2="14" y2="12" class="bond-line" />
            <circle cx="-14" cy="12" r="9" class="atom-h" />
            <text x="-14" y="12" class="atom-text text-h">H</text>
            <circle cx="14" cy="12" r="9" class="atom-h" />
            <text x="14" y="12" class="atom-text text-h">H</text>
            <circle cx="0" cy="0" r="14" class="atom-o" />
            <text x="0" y="0" class="atom-text text-o">O</text>
          </g>

          
          <g id="phys-m3" class="atom-group" transform="translate(100, 130)">
            <line x1="0" y1="0" x2="-14" y2="-12" class="bond-line" />
            <line x1="0" y1="0" x2="14" y2="-12" class="bond-line" />
            <circle cx="-14" cy="-12" r="9" class="atom-h" />
            <text x="-14" y="-12" class="atom-text text-h">H</text>
            <circle cx="14" cy="-12" r="9" class="atom-h" />
            <text x="14" y="-12" class="atom-text text-h">H</text>
            <circle cx="0" cy="0" r="14" class="atom-o" />
            <text x="0" y="0" class="atom-text text-o">O</text>
          </g>
        </svg>
      </div>

      <div class="badge badge-physical" id="phys-label">
        Ice (Lattice)
      </div>
    </div>

    
    <div class="panel">
      <div class="panel-title title-chemical">Chemical Reaction</div>
      
      <div class="stage-box">
        <svg class="stage-svg" viewBox="0 0 200 190">
          
          <g id="chem-o1" class="atom-group" transform="translate(65, 75)">
            <circle cx="0" cy="0" r="14" class="atom-o" />
            <text x="0" y="0" class="atom-text text-o">O</text>
          </g>
          <g id="chem-o2" class="atom-group" transform="translate(135, 75)">
            <circle cx="0" cy="0" r="14" class="atom-o" />
            <text x="0" y="0" class="atom-text text-o">O</text>
          </g>

          
          <g id="chem-h1" class="atom-group" transform="translate(48, 100)">
            <circle cx="0" cy="0" r="9" class="atom-h" />
            <text x="0" y="0" class="atom-text text-h">H</text>
          </g>
          <g id="chem-h2" class="atom-group" transform="translate(82, 100)">
            <circle cx="0" cy="0" r="9" class="atom-h" />
            <text x="0" y="0" class="atom-text text-h">H</text>
          </g>
          <g id="chem-h3" class="atom-group" transform="translate(118, 100)">
            <circle cx="0" cy="0" r="9" class="atom-h" />
            <text x="0" y="0" class="atom-text text-h">H</text>
          </g>
          <g id="chem-h4" class="atom-group" transform="translate(152, 100)">
            <circle cx="0" cy="0" r="9" class="atom-h" />
            <text x="0" y="0" class="atom-text text-h">H</text>
          </g>

          
          <line id="chem-bond-h2a" x1="45" y1="135" x2="65" y2="135" class="bond-line" style="opacity: 0;" />
          <line id="chem-bond-h2b" x1="135" y1="135" x2="155" y2="135" class="bond-line" style="opacity: 0;" />
          <line id="chem-bond-o2-1" x1="90" y1="52" x2="110" y2="52" class="bond-line" style="opacity: 0;" />
          <line id="chem-bond-o2-2" x1="90" y1="58" x2="110" y2="58" class="bond-line" style="opacity: 0;" />

          
          <line id="init-b1" x1="65" y1="75" x2="48" y2="100" class="bond-line" />
          <line id="init-b2" x1="65" y1="75" x2="82" y2="100" class="bond-line" />
          <line id="init-b3" x1="135" y1="75" x2="118" y2="100" class="bond-line" />
          <line id="init-b4" x1="135" y1="75" x2="152" y2="100" class="bond-line" />
        </svg>
      </div>

      <div class="badge badge-chemical" id="chem-label">
        2 H₂O Molecules
      </div>
    </div>

  </div>

  
  <div class="legend">
    <div class="legend-item">
      <span class="legend-dot dot-o"></span> Oxygen (O)
    </div>
    <div class="legend-item">
      <span class="legend-dot dot-h"></span> Hydrogen (H)
    </div>
  </div>

  <script>
    let currentStep = 0;

    function setStep(step) {
      currentStep = step;
      document.getElementById('btnBefore').classList.toggle('active', step === 0);
      document.getElementById('btnAfter').classList.toggle('active', step === 1);

      // Physical Change Visuals
      const pm1 = document.getElementById('phys-m1');
      const pm2 = document.getElementById('phys-m2');
      const pm3 = document.getElementById('phys-m3');
      const physLabel = document.getElementById('phys-label');

      // Chemical Reaction Visuals
      const co1 = document.getElementById('chem-o1');
      const co2 = document.getElementById('chem-o2');
      const ch1 = document.getElementById('chem-h1');
      const ch2 = document.getElementById('chem-h2');
      const ch3 = document.getElementById('chem-h3');
      const ch4 = document.getElementById('chem-h4');
      
      const bH2a = document.getElementById('chem-bond-h2a');
      const bH2b = document.getElementById('chem-bond-h2b');
      const bO2_1 = document.getElementById('chem-bond-o2-1');
      const bO2_2 = document.getElementById('chem-bond-o2-2');

      const ib1 = document.getElementById('init-b1');
      const ib2 = document.getElementById('init-b2');
      const ib3 = document.getElementById('init-b3');
      const ib4 = document.getElementById('init-b4');
      const chemLabel = document.getElementById('chem-label');

      if (step === 0) {
        // --- STEP 0: BEFORE ---
        // Physical: Tight ice arrangement
        pm1.setAttribute('transform', 'translate(60, 65) rotate(0)');
        pm2.setAttribute('transform', 'translate(140, 65) rotate(0)');
        pm3.setAttribute('transform', 'translate(100, 130) rotate(0)');
        physLabel.textContent = 'Solid Ice: Fixed lattice (H₂O)';

        // Chemical: Intact 2 H2O
        co1.setAttribute('transform', 'translate(65, 75)');
        co2.setAttribute('transform', 'translate(135, 75)');
        ch1.setAttribute('transform', 'translate(48, 100)');
        ch2.setAttribute('transform', 'translate(82, 100)');
        ch3.setAttribute('transform', 'translate(118, 100)');
        ch4.setAttribute('transform', 'translate(152, 100)');

        ib1.style.opacity = '1';
        ib2.style.opacity = '1';
        ib3.style.opacity = '1';
        ib4.style.opacity = '1';

        bH2a.style.opacity = '0';
        bH2b.style.opacity = '0';
        bO2_1.style.opacity = '0';
        bO2_2.style.opacity = '0';

        chemLabel.textContent = 'Reactants: 2 H₂O molecules';
      } else {
        // --- STEP 1: AFTER ---
        // Physical: Liquid water (same molecules, shifted)
        pm1.setAttribute('transform', 'translate(45, 80) rotate(-25)');
        pm2.setAttribute('transform', 'translate(145, 120) rotate(35)');
        pm3.setAttribute('transform', 'translate(110, 45) rotate(15)');
        physLabel.textContent = 'Liquid: Same molecules (H₂O)';

        // Chemical: 2 H2 + O2 formed
        co1.setAttribute('transform', 'translate(88, 55)');
        co2.setAttribute('transform', 'translate(112, 55)');
        ch1.setAttribute('transform', 'translate(45, 135)');
        ch2.setAttribute('transform', 'translate(65, 135)');
        ch3.setAttribute('transform', 'translate(135, 135)');
        ch4.setAttribute('transform', 'translate(155, 135)');

        ib1.style.opacity = '0';
        ib2.style.opacity = '0';
        ib3.style.opacity = '0';
        ib4.style.opacity = '0';

        bH2a.style.opacity = '1';
        bH2b.style.opacity = '1';
        bO2_1.style.opacity = '1';
        bO2_2.style.opacity = '1';

        chemLabel.textContent = 'New products: 2 H₂ + O₂';
      }
    }

    // Auto-advance slowly to introduce concept, user can freely click
    let timer = setInterval(() => {
      setStep((currentStep + 1) % 2);
    }, 3800);

    // Stop auto-timer on user interaction
    ['btnBefore', 'btnAfter'].forEach(id => {
      document.getElementById(id).addEventListener('click', () => {
        clearInterval(timer);
      });
    });
  </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: #1e293b;
      background: #f8fafc;
      padding: 10px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    /* Controls Bar */
    .controls {
      display: flex;
      justify-content: center;
      gap: 6px;
      flex-wrap: wrap;
    }
    .filter-btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      padding: 4px 12px;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      transition: background 0.2s, color 0.2s, border-color 0.2s;
    }
    .filter-btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }

    /* 3-Column Grid */
    .cards-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 8px;
      width: 100%;
    }
    @media (max-width: 480px) {
      .cards-grid {
        grid-template-columns: 1fr;
        gap: 10px;
      }
    }

    /* State Card */
    .state-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 6px;
    }

    /* Header Badges */
    .badge {
      font-size: 12px;
      font-weight: 700;
      padding: 3px 10px;
      border-radius: 12px;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }
    .badge-solid { background: #e0f2fe; color: #0369a1; }
    .badge-liquid { background: #ccfbf1; color: #0f766e; }
    .badge-gas { background: #ede9fe; color: #6d28d9; }

    /* Particle Box SVG */
    .particle-box {
      width: 100%;
      max-width: 150px;
      aspect-ratio: 1;
      background: #f1f5f9;
      border: 2px solid #cbd5e1;
      border-radius: 8px;
      overflow: hidden;
      display: block;
    }

    /* Property Tags */
    .prop-list {
      width: 100%;
      display: flex;
      flex-direction: column;
      gap: 4px;
      font-size: 11px;
    }
    .prop-row {
      display: flex;
      justify-content: space-between;
      align-items: center;
      padding: 3px 6px;
      border-radius: 4px;
      background: #f8fafc;
      transition: background 0.2s;
    }
    .prop-label {
      color: #64748b;
      font-weight: 600;
    }
    .prop-val {
      font-weight: 600;
      color: #0f172a;
    }

    /* Highlight Filter States */
    body[data-focus="energy"] .prop-energy { background: #fef3c7; }
    body[data-focus="motion"] .prop-motion { background: #dbeafe; }
    body[data-focus="shape"] .prop-shape { background: #e0e7ff; }

    /* Energy Bar Metric */
    .energy-bar-wrap {
      width: 100%;
      height: 4px;
      background: #e2e8f0;
      border-radius: 2px;
      overflow: hidden;
    }
    .energy-bar {
      height: 100%;
      border-radius: 2px;
      transition: width 0.3s ease;
    }
    .eb-solid { width: 25%; background: #38bdf8; }
    .eb-liquid { width: 60%; background: #2dd4bf; }
    .eb-gas { width: 100%; background: #a855f7; }

    /* Keyframe Animations */
    @keyframes vibrate {
      0%, 100% { transform: translate(0, 0); }
      25% { transform: translate(0.6px, -0.6px); }
      50% { transform: translate(-0.6px, 0.4px); }
      75% { transform: translate(0.4px, 0.6px); }
    }
    .vib { animation: vibrate 0.2s infinite ease-in-out; transform-origin: center; }

    @keyframes slide1 { 0%, 100% { transform: translate(0,0); } 50% { transform: translate(3px, -2px); } }
    @keyframes slide2 { 0%, 100% { transform: translate(0,0); } 50% { transform: translate(-3px, 2px); } }
    @keyframes slide3 { 0%, 100% { transform: translate(0,0); } 50% { transform: translate(2px, 3px); } }
    .flow-1 { animation: slide1 2.2s infinite ease-in-out; }
    .flow-2 { animation: slide2 1.8s infinite ease-in-out; }
    .flow-3 { animation: slide3 2.5s infinite ease-in-out; }

    @keyframes gas1 { 0% { transform: translate(0,0); } 50% { transform: translate(45px,-25px); } 100% { transform: translate(0,0); } }
    @keyframes gas2 { 0% { transform: translate(0,0); } 50% { transform: translate(-35px,40px); } 100% { transform: translate(0,0); } }
    @keyframes gas3 { 0% { transform: translate(0,0); } 50% { transform: translate(30px,35px); } 100% { transform: translate(0,0); } }
    @keyframes gas4 { 0% { transform: translate(0,0); } 50% { transform: translate(-40px,-30px); } 100% { transform: translate(0,0); } }
    @keyframes gas5 { 0% { transform: translate(0,0); } 50% { transform: translate(20px,-40px); } 100% { transform: translate(0,0); } }
    .gas-p1 { animation: gas1 2s infinite linear; }
    .gas-p2 { animation: gas2 2.4s infinite linear; }
    .gas-p3 { animation: gas3 2.1s infinite linear; }
    .gas-p4 { animation: gas4 2.6s infinite linear; }
    .gas-p5 { animation: gas5 1.9s infinite linear; }
  </style>
</head>
<body data-focus="all">

  
  <div class="controls">
    <button class="filter-btn active" onclick="setFocus('all')">Overview</button>
    <button class="filter-btn" onclick="setFocus('motion')">Movement</button>
    <button class="filter-btn" onclick="setFocus('energy')">Kinetic Energy</button>
    <button class="filter-btn" onclick="setFocus('shape')">Shape & Volume</button>
  </div>

  
  <div class="cards-grid">
    
    
    <div class="state-card">
      <div class="badge badge-solid">Solid</div>
      <svg class="particle-box" viewBox="0 0 100 100">
        <defs>
          <radialGradient id="solidGrad" cx="35%" cy="35%" r="65%">
            <stop offset="0%" stop-color="#7dd3fc"/>
            <stop offset="100%" stop-color="#0284c7"/>
          </radialGradient>
        </defs>
        
        <g class="vib" fill="url(#solidGrad)" stroke="#0369a1" stroke-width="0.5">
          
          <circle cx="16" cy="16" r="7.5"/> <circle cx="33" cy="16" r="7.5"/> <circle cx="50" cy="16" r="7.5"/> <circle cx="67" cy="16" r="7.5"/> <circle cx="84" cy="16" r="7.5"/>
          
          <circle cx="16" cy="33" r="7.5"/> <circle cx="33" cy="33" r="7.5"/> <circle cx="50" cy="33" r="7.5"/> <circle cx="67" cy="33" r="7.5"/> <circle cx="84" cy="33" r="7.5"/>
          
          <circle cx="16" cy="50" r="7.5"/> <circle cx="33" cy="50" r="7.5"/> <circle cx="50" cy="50" r="7.5"/> <circle cx="67" cy="50" r="7.5"/> <circle cx="84" cy="50" r="7.5"/>
          
          <circle cx="16" cy="67" r="7.5"/> <circle cx="33" cy="67" r="7.5"/> <circle cx="50" cy="67" r="7.5"/> <circle cx="67" cy="67" r="7.5"/> <circle cx="84" cy="67" r="7.5"/>
          
          <circle cx="16" cy="84" r="7.5"/> <circle cx="33" cy="84" r="7.5"/> <circle cx="50" cy="84" r="7.5"/> <circle cx="67" cy="84" r="7.5"/> <circle cx="84" cy="84" r="7.5"/>
        </g>
      </svg>
      <div class="energy-bar-wrap"><div class="energy-bar eb-solid"></div></div>
      <div class="prop-list">
        <div class="prop-row prop-motion"><span class="prop-label">Motion</span><span class="prop-val">Vibrates in place</span></div>
        <div class="prop-row prop-energy"><span class="prop-label">Energy</span><span class="prop-val">Lowest</span></div>
        <div class="prop-row prop-shape"><span class="prop-label">Shape</span><span class="prop-val">Fixed</span></div>
      </div>
    </div>

    
    <div class="state-card">
      <div class="badge badge-liquid">Liquid</div>
      <svg class="particle-box" viewBox="0 0 100 100">
        <defs>
          <radialGradient id="liqGrad" cx="35%" cy="35%" r="65%">
            <stop offset="0%" stop-color="#5eead4"/>
            <stop offset="100%" stop-color="#0d9488"/>
          </radialGradient>
        </defs>
        
        <g fill="url(#liqGrad)" stroke="#0f766e" stroke-width="0.5">
          <g class="flow-1">
            <circle cx="18" cy="84" r="7.5"/> <circle cx="34" cy="85" r="7.5"/> <circle cx="51" cy="83" r="7.5"/> <circle cx="68" cy="85" r="7.5"/> <circle cx="84" cy="84" r="7.5"/>
          </g>
          <g class="flow-2">
            <circle cx="25" cy="69" r="7.5"/> <circle cx="43" cy="68" r="7.5"/> <circle cx="60" cy="70" r="7.5"/> <circle cx="77" cy="69" r="7.5"/>
          </g>
          <g class="flow-3">
            <circle cx="18" cy="54" r="7.5"/> <circle cx="35" cy="53" r="7.5"/> <circle cx="53" cy="54" r="7.5"/> <circle cx="70" cy="53" r="7.5"/> <circle cx="84" cy="56" r="7.5"/>
          </g>
          <g class="flow-1">
            <circle cx="30" cy="38" r="7.5"/> <circle cx="48" cy="39" r="7.5"/> <circle cx="66" cy="38" r="7.5"/>
          </g>
        </g>
      </svg>
      <div class="energy-bar-wrap"><div class="energy-bar eb-liquid"></div></div>
      <div class="prop-list">
        <div class="prop-row prop-motion"><span class="prop-label">Motion</span><span class="prop-val">Slides past</span></div>
        <div class="prop-row prop-energy"><span class="prop-label">Energy</span><span class="prop-val">Medium</span></div>
        <div class="prop-row prop-shape"><span class="prop-label">Shape</span><span class="prop-val">Fills bottom</span></div>
      </div>
    </div>

    
    <div class="state-card">
      <div class="badge badge-gas">Gas</div>
      <svg class="particle-box" viewBox="0 0 100 100">
        <defs>
          <radialGradient id="gasGrad" cx="35%" cy="35%" r="65%">
            <stop offset="0%" stop-color="#c4b5fd"/>
            <stop offset="100%" stop-color="#7c3aed"/>
          </radialGradient>
        </defs>
        
        <g fill="url(#gasGrad)" stroke="#6d28d9" stroke-width="0.5">
          <g class="gas-p1"><circle cx="20" cy="25" r="7.5"/><line x1="20" y1="25" x2="32" y2="18" stroke="#a78bfa" stroke-width="1.5" stroke-dasharray="2 1"/></g>
          <g class="gas-p2"><circle cx="75" cy="20" r="7.5"/><line x1="75" y1="20" x2="62" y2="35" stroke="#a78bfa" stroke-width="1.5" stroke-dasharray="2 1"/></g>
          <g class="gas-p3"><circle cx="45" cy="50" r="7.5"/><line x1="45" y1="50" x2="58" y2="62" stroke="#a78bfa" stroke-width="1.5" stroke-dasharray="2 1"/></g>
          <g class="gas-p4"><circle cx="80" cy="75" r="7.5"/><line x1="80" y1="75" x2="65" y2="65" stroke="#a78bfa" stroke-width="1.5" stroke-dasharray="2 1"/></g>
          <g class="gas-p5"><circle cx="20" cy="80" r="7.5"/><line x1="20" y1="80" x2="30" y2="65" stroke="#a78bfa" stroke-width="1.5" stroke-dasharray="2 1"/></g>
        </g>
      </svg>
      <div class="energy-bar-wrap"><div class="energy-bar eb-gas"></div></div>
      <div class="prop-list">
        <div class="prop-row prop-motion"><span class="prop-label">Motion</span><span class="prop-val">Rapid & random</span></div>
        <div class="prop-row prop-energy"><span class="prop-label">Energy</span><span class="prop-val">Highest</span></div>
        <div class="prop-row prop-shape"><span class="prop-label">Shape</span><span class="prop-val">Fills container</span></div>
      </div>
    </div>

  </div>

  <script>
    function setFocus(type) {
      document.body.setAttribute('data-focus', type);
      document.querySelectorAll('.filter-btn').forEach(btn => {
        btn.classList.toggle('active', btn.getAttribute('onclick').includes(`'${type}'`));
      });
    }
  </script>
</body>
</html>

UK-GCSE-SCIENCE-CHEM-SBM

Child standards (4)

Aligned learning resources

Related diagrams