<!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">
  <title>Prefix Conversion Solver</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      -webkit-tap-highlight-color: transparent;
    }

    body {
      background: #ffffff;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      min-height: 100%;
    }

    .solver-app {
      width: 100%;
      max-width: 520px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    /* Example selector tabs */
    .tab-group {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
      background: #f1f5f9;
      padding: 4px;
      border-radius: 10px;
    }

    .tab-btn {
      padding: 8px 12px;
      border: 1px solid transparent;
      border-radius: 8px;
      background: transparent;
      color: #64748b;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: background 0.2s ease, color 0.2s ease, box-shadow 0.2s ease;
    }

    .tab-btn.active {
      background: #ffffff;
      color: #0284c7;
      border-color: #e2e8f0;
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
    }

    /* Step Stepper Navigation */
    .stepper-nav {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 6px;
    }

    .step-pills {
      display: flex;
      gap: 6px;
      flex: 1;
    }

    .step-pill {
      flex: 1;
      padding: 6px 4px;
      font-size: 12px;
      font-weight: 700;
      border-radius: 6px;
      border: 1px solid #e2e8f0;
      background: #f8fafc;
      color: #64748b;
      cursor: pointer;
      text-align: center;
      transition: background 0.2s ease, color 0.2s ease, border-color 0.2s ease;
    }

    .step-pill.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }

    .nav-btn {
      padding: 6px 12px;
      font-size: 13px;
      font-weight: 700;
      border-radius: 6px;
      border: 1px solid #e2e8f0;
      background: #ffffff;
      color: #1e2945;
      cursor: pointer;
      transition: background 0.15s ease;
    }

    .nav-btn:disabled {
      opacity: 0.35;
      cursor: not-allowed;
    }

    /* Target Question Banner */
    .target-banner {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 10px 14px;
      display: flex;
      align-items: center;
      justify-content: space-between;
    }

    .target-label {
      font-size: 12px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #64748b;
    }

    .target-math {
      font-size: 16px;
      font-weight: 700;
      color: #0f172a;
    }

    /* Step Sequence Container */
    .steps-container {
      display: flex;
      flex-direction: column;
      gap: 8px;
      min-height: 220px;
    }

    .step-row {
      display: flex;
      align-items: center;
      gap: 10px;
      padding: 10px 12px;
      border-radius: 8px;
      border: 1px solid #e2e8f0;
      background: #ffffff;
      opacity: 0.3;
      transition: opacity 0.25s ease, background 0.25s ease, border-color 0.25s ease, box-shadow 0.25s ease;
    }

    .step-row.visible {
      opacity: 0.7;
    }

    .step-row.active-step {
      opacity: 1;
      background: #f0f9ff;
      border-color: #38bdf8;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.08);
    }

    .step-num-badge {
      width: 26px;
      height: 26px;
      border-radius: 50%;
      background: #e2e8f0;
      color: #475569;
      font-size: 12px;
      font-weight: 800;
      display: flex;
      align-items: center;
      justify-content: center;
      flex-shrink: 0;
      transition: background 0.2s ease, color 0.2s ease;
    }

    .active-step .step-num-badge {
      background: #0284c7;
      color: #ffffff;
    }

    .step-content {
      flex: 1;
      display: flex;
      flex-direction: column;
      gap: 2px;
    }

    .step-desc {
      font-size: 11px;
      font-weight: 700;
      color: #64748b;
      text-transform: uppercase;
      letter-spacing: 0.3px;
    }

    .active-step .step-desc {
      color: #0284c7;
    }

    .step-formula {
      font-size: 15px;
      font-weight: 700;
      color: #1e2945;
      display: flex;
      align-items: center;
      flex-wrap: wrap;
      gap: 4px;
    }

    .highlight {
      color: #0284c7;
      background: #e0f2fe;
      padding: 1px 5px;
      border-radius: 4px;
    }

    .result-highlight {
      color: #047857;
      background: #d1fae5;
      padding: 2px 6px;
      border-radius: 4px;
      font-weight: 800;
    }
  </style>
</head>
<body>

  <div class="solver-app">
    
    <div class="tab-group">
      <button class="tab-btn active" id="tabEx1" onclick="setExample(0)">
        <span>450 nm → m</span>
      </button>
      <button class="tab-btn" id="tabEx2" onclick="setExample(1)">
        <span>0.008 A → μA</span>
      </button>
    </div>

    
    <div class="stepper-nav">
      <button class="nav-btn" id="prevBtn" onclick="prevStep()">←</button>
      <div class="step-pills">
        <button class="step-pill active" id="pill0" onclick="goToStep(0)">Step 1</button>
        <button class="step-pill" id="pill1" onclick="goToStep(1)">Step 2</button>
        <button class="step-pill" id="pill2" onclick="goToStep(2)">Step 3</button>
      </div>
      <button class="nav-btn" id="nextBtn" onclick="nextStep()">→</button>
    </div>

    
    <div class="target-banner">
      <span class="target-label" id="targetType">Convert</span>
      <span class="target-math" id="targetMath">450 nm → meters</span>
    </div>

    
    <div class="steps-container" id="stepsContainer">
      
      <div class="step-row visible active-step" id="row0">
        <div class="step-num-badge">1</div>
        <div class="step-content">
          <div class="step-desc" id="s1Desc">Prefix Multiplier</div>
          <div class="step-formula" id="s1Formula">
            nano (n) = <span class="highlight">10<sup>-9</sup></span>
          </div>
        </div>
      </div>

      
      <div class="step-row" id="row1">
        <div class="step-num-badge">2</div>
        <div class="step-content">
          <div class="step-desc" id="s2Desc">Direct Substitution</div>
          <div class="step-formula" id="s2Formula">
            450 × <span class="highlight">10<sup>-9</sup></span> m
          </div>
        </div>
      </div>

      
      <div class="step-row" id="row2">
        <div class="step-num-badge">3</div>
        <div class="step-content">
          <div class="step-desc" id="s3Desc">Standard Form</div>
          <div class="step-formula" id="s3Formula">
            = <span class="result-highlight">4.5 × 10<sup>-7</sup> m</span>
          </div>
        </div>
      </div>
    </div>
  </div>

  <script>
    const examples = [
      {
        targetLabel: "Prefix to Base",
        targetMath: "450 nm → meters",
        steps: [
          { desc: "Prefix Multiplier", formula: 'nano (n) = <span class="highlight">10<sup>-9</sup></span>' },
          { desc: "Direct Substitution", formula: '450 × <span class="highlight">10<sup>-9</sup></span> m' },
          { desc: "Standard Form", formula: '= <span class="result-highlight">4.5 × 10<sup>-7</sup> m</span>' }
        ]
      },
      {
        targetLabel: "Base to Prefix",
        targetMath: "0.008 A → microamperes (μA)",
        steps: [
          { desc: "Conversion Factor", formula: 'Base → μ = multiply by <span class="highlight">10<sup>6</sup></span>' },
          { desc: "Multiply", formula: '0.008 × <span class="highlight">1,000,000</span> μA' },
          { desc: "Final Result", formula: '= <span class="result-highlight">8,000 μA</span> (8 × 10<sup>3</sup> μA)' }
        ]
      }
    ];

    let currentEx = 0;
    let currentStep = 0;

    function render() {
      const ex = examples[currentEx];

      // Update Tabs
      document.getElementById('tabEx1').classList.toggle('active', currentEx === 0);
      document.getElementById('tabEx2').classList.toggle('active', currentEx === 1);

      // Update Target Banner
      document.getElementById('targetType').textContent = ex.targetLabel;
      document.getElementById('targetMath').textContent = ex.targetMath;

      // Update Step Data
      for (let i = 0; i < 3; i++) {
        document.getElementById(`s${i + 1}Desc`).textContent = ex.steps[i].desc;
        document.getElementById(`s${i + 1}Formula`).innerHTML = ex.steps[i].formula;

        const row = document.getElementById(`row${i}`);
        const pill = document.getElementById(`pill${i}`);

        // State classes
        const isPastOrCurrent = i <= currentStep;
        const isCurrent = i === currentStep;

        row.classList.toggle('visible', isPastOrCurrent);
        row.classList.toggle('active-step', isCurrent);
        pill.classList.toggle('active', isCurrent);
      }

      // Update Buttons
      document.getElementById('prevBtn').disabled = currentStep === 0;
      document.getElementById('nextBtn').disabled = currentStep === 2;
    }

    function setExample(idx) {
      if (currentEx === idx) return;
      currentEx = idx;
      currentStep = 0;
      render();
    }

    function goToStep(idx) {
      currentStep = idx;
      render();
    }

    function nextStep() {
      if (currentStep < 2) {
        currentStep++;
        render();
      }
    }

    function prevStep() {
      if (currentStep > 0) {
        currentStep--;
        render();
      }
    }

    // Init
    render();
  </script>
</body>
</html>

Prefixes in the SI System: Kilo, Milli, Micro and Nano

<!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="4:5">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      user-select: none;
      -webkit-user-select: none;
    }
    body {
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
      color: #1e2945;
      background: transparent;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 8px 4px;
      width: 100%;
      min-height: 100%;
    }
    .diagram-wrap {
      width: 100%;
      max-width: 350px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }
    .ladder-container {
      display: grid;
      grid-template-columns: 32px 1fr 32px;
      gap: 6px;
      align-items: stretch;
    }
    .side-rail {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      border-radius: 8px;
      padding: 6px 2px;
      font-size: 10px;
      font-weight: 700;
      text-align: center;
      line-height: 1.1;
    }
    .rail-left {
      background: #eff6ff;
      border: 1px dashed #93c5fd;
      color: #1d4ed8;
    }
    .rail-right {
      background: #f0fdf4;
      border: 1px dashed #86efac;
      color: #15803d;
    }
    .rail-label {
      writing-mode: vertical-rl;
      transform: rotate(180deg);
      letter-spacing: 0.5px;
      text-transform: uppercase;
      font-size: 9px;
      margin: 4px 0;
    }
    .rail-right .rail-label {
      transform: none;
    }
    .rail-arrow {
      font-size: 14px;
      font-weight: 900;
    }
    .ladder {
      display: flex;
      flex-direction: column;
      gap: 4px;
    }
    .prefix-row {
      display: grid;
      grid-template-columns: 80px 42px 1fr;
      align-items: center;
      padding: 5px 8px;
      background: #ffffff;
      border: 1.5px solid #e6e6e6;
      border-radius: 8px;
      cursor: pointer;
      transition: background 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease;
      font-size: 12px;
    }
    .prefix-row:hover {
      background: #f8fafc;
      border-color: #cbd5e1;
    }
    .prefix-row.active {
      border-color: #0284c7;
      background: #f0f9ff;
      box-shadow: 0 0 0 2px rgba(2, 132, 199, 0.2);
    }
    .prefix-name {
      font-weight: 700;
      color: #1e2945;
      display: flex;
      align-items: center;
      gap: 4px;
    }
    .prefix-symbol {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      width: 22px;
      height: 22px;
      border-radius: 4px;
      background: #f1f5f9;
      font-family: "Courier New", monospace;
      font-weight: 700;
      font-size: 13px;
      color: #0f172a;
    }
    .prefix-row.active .prefix-symbol {
      background: #0284c7;
      color: #ffffff;
    }
    .prefix-power {
      font-family: "Courier New", monospace;
      font-weight: 700;
      color: #475569;
      font-size: 12px;
      text-align: right;
    }
    .prefix-row.active .prefix-power {
      color: #0369a1;
      font-weight: 800;
    }
    .base-row {
      background: #f8fafc;
      border-style: dashed;
    }
    .info-card {
      height: 72px;
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 12px;
      display: flex;
      flex-direction: column;
      justify-content: center;
      gap: 3px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }
    .info-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 13px;
      font-weight: 700;
    }
    .info-title {
      color: #0284c7;
      display: flex;
      align-items: center;
      gap: 6px;
    }
    .info-multiplier {
      font-family: "Courier New", monospace;
      font-size: 11px;
      color: #64748b;
      font-weight: 600;
    }
    .info-example {
      font-size: 12px;
      color: #334155;
      display: flex;
      align-items: center;
      gap: 6px;
      white-space: nowrap;
      overflow: hidden;
      text-overflow: ellipsis;
    }
    .info-tag {
      display: inline-block;
      padding: 1px 5px;
      border-radius: 4px;
      background: #f1f5f9;
      font-size: 10px;
      font-weight: 700;
      color: #475569;
      flex-shrink: 0;
    }
  </style>
</head>
<body>
  <div class="diagram-wrap">
    <div class="ladder-container">
      
      <div class="side-rail rail-left" title="Converting to larger prefix: divide by factor">
        <span class="rail-arrow">▲</span>
        <span class="rail-label">Divide ÷ 10ⁿ</span>
        <span class="rail-arrow">▲</span>
      </div>

      
      <div class="ladder" id="ladder">
        <div class="prefix-row" data-idx="0">
          <div class="prefix-name">Mega</div>
          <div class="prefix-symbol">M</div>
          <div class="prefix-power">10⁶</div>
        </div>
        <div class="prefix-row" data-idx="1">
          <div class="prefix-name">Kilo</div>
          <div class="prefix-symbol">k</div>
          <div class="prefix-power">10³</div>
        </div>
        <div class="prefix-row base-row active" data-idx="2">
          <div class="prefix-name">Base</div>
          <div class="prefix-symbol">—</div>
          <div class="prefix-power">10⁰</div>
        </div>
        <div class="prefix-row" data-idx="3">
          <div class="prefix-name">Centi</div>
          <div class="prefix-symbol">c</div>
          <div class="prefix-power">10⁻²</div>
        </div>
        <div class="prefix-row" data-idx="4">
          <div class="prefix-name">Milli</div>
          <div class="prefix-symbol">m</div>
          <div class="prefix-power">10⁻³</div>
        </div>
        <div class="prefix-row" data-idx="5">
          <div class="prefix-name">Micro</div>
          <div class="prefix-symbol">μ</div>
          <div class="prefix-power">10⁻⁶</div>
        </div>
        <div class="prefix-row" data-idx="6">
          <div class="prefix-name">Nano</div>
          <div class="prefix-symbol">n</div>
          <div class="prefix-power">10⁻⁹</div>
        </div>
      </div>

      
      <div class="side-rail rail-right" title="Converting to smaller prefix: multiply by factor">
        <span class="rail-arrow">▼</span>
        <span class="rail-label">Multiply × 10ⁿ</span>
        <span class="rail-arrow">▼</span>
      </div>
    </div>

    
    <div class="info-card" id="infoCard">
      <div class="info-header">
        <span class="info-title" id="infoTitle">Base Unit (10⁰)</span>
        <span class="info-multiplier" id="infoMultiplier">= 1</span>
      </div>
      <div class="info-example" id="infoExample">
        <span class="info-tag">EXAMPLE</span>
        <span id="exampleText">📏 Metre rule / 1 litre bottle</span>
      </div>
    </div>
  </div>

  <script>
    const data = [
      {
        title: "Mega (M = 10⁶)",
        mult: "= 1,000,000",
        tag: "POWER / ENERGY",
        text: "⚡ Power station output (MW)"
      },
      {
        title: "Kilo (k = 10³)",
        mult: "= 1,000",
        tag: "DISTANCE / MASS",
        text: "🏃 5 km run = 5,000 m"
      },
      {
        title: "Base Unit (10⁰)",
        mult: "= 1",
        tag: "STANDARD",
        text: "📏 1 metre (m) / 1 gram (g)"
      },
      {
        title: "Centi (c = 10⁻²)",
        mult: "= 0.01 (1/100)",
        tag: "EVERYDAY",
        text: "✏️ Pencil width = ~1 cm"
      },
      {
        title: "Milli (m = 10⁻³)",
        mult: "= 0.001 (1/1000)",
        tag: "SMALL SCALE",
        text: "🐜 Ant length = ~3 mm"
      },
      {
        title: "Micro (μ = 10⁻⁶)",
        mult: "= 0.000001",
        tag: "MICROSCOPIC",
        text: "🩸 Red blood cell = ~7 μm"
      },
      {
        title: "Nano (n = 10⁻⁹)",
        mult: "= 0.000000001",
        tag: "NANOSCALE",
        text: "🧬 DNA strand width = ~2 nm"
      }
    ];

    const rows = document.querySelectorAll('.prefix-row');
    const infoTitle = document.getElementById('infoTitle');
    const infoMultiplier = document.getElementById('infoMultiplier');
    const infoExample = document.getElementById('infoExample');
    const exampleText = document.getElementById('exampleText');

    function selectPrefix(index) {
      rows.forEach((r, i) => {
        r.classList.toggle('active', i === index);
      });
      const item = data[index];
      infoTitle.textContent = item.title;
      infoMultiplier.textContent = item.mult;
      exampleText.textContent = item.text;
    }

    rows.forEach((row) => {
      row.addEventListener('click', () => {
        const idx = parseInt(row.getAttribute('data-idx'), 10);
        selectPrefix(idx);
      });
    });
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #f8fafc;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 12px;
      min-height: 100%;
    }
    .container {
      width: 100%;
      max-width: 580px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 10px;
    }
    .btn-group {
      display: flex;
      gap: 6px;
      flex-wrap: wrap;
      justify-content: center;
    }
    .tab-btn {
      background: #ffffff;
      border: 1.5px solid #cbd5e1;
      border-radius: 20px;
      padding: 5px 12px;
      font-size: 13px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 5px;
      transition: all 0.2s ease;
    }
    .tab-btn:hover {
      background: #f1f5f9;
      border-color: #94a3b8;
    }
    .tab-btn.active {
      background: #1e2945;
      color: #ffffff;
      border-color: #1e2945;
    }
    .tab-btn.active.btn-correct {
      background: #16a34a;
      border-color: #16a34a;
    }
    .tab-btn.active.btn-error {
      background: #dc2626;
      border-color: #dc2626;
    }
    svg {
      width: 100%;
      height: auto;
      max-height: 380px;
      overflow: visible;
    }
    .sightline {
      transition: opacity 0.3s ease;
    }
    .sightline.dimmed {
      opacity: 0.12;
    }
    .eye-group {
      cursor: pointer;
    }
  </style>
</head>
<body>

<div class="container">
  <div class="btn-group">
    <button class="tab-btn active" id="btn-all" onclick="setMode('all')">Show All</button>
    <button class="tab-btn btn-error" id="btn-high" onclick="setMode('high')">👁️ High (26.2 mL)</button>
    <button class="tab-btn btn-correct" id="btn-center" onclick="setMode('center')">👁️ Eye Level (25.0 mL)</button>
    <button class="tab-btn btn-error" id="btn-low" onclick="setMode('low')">👁️ Low (24.2 mL)</button>
  </div>

  <svg viewBox="0 0 540 370">
    <defs>
      
      <linearGradient id="glassGrad" x1="0" y1="0" x2="1" y2="0">
        <stop offset="0%" stop-color="#ffffff" stop-opacity="0.8"/>
        <stop offset="15%" stop-color="#cbd5e1" stop-opacity="0.3"/>
        <stop offset="85%" stop-color="#cbd5e1" stop-opacity="0.2"/>
        <stop offset="100%" stop-color="#94a3b8" stop-opacity="0.6"/>
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             Q 160 205, 209 170 
             L 209 320 
             L 111 320 Z" 
          fill="url(#liquidGrad)" opacity="0.85"/>

    
    
    <path d="M 111 170 Q 160 205, 209 170 Q 160 178, 111 170 Z" fill="url(#meniscusGrad)" opacity="0.9"/>
    
    <path d="M 111 170 Q 160 205, 209 170" fill="none" stroke="#0369a1" stroke-width="2.5"/>
    <path d="M 111 170 Q 160 176, 209 170" fill="none" stroke="#38bdf8" stroke-width="1.5" stroke-dasharray="2 2"/>

    
    <rect x="110" y="30" width="100" height="290" rx="8" fill="url(#glassGrad)" pointer-events="none"/>
    <ellipse cx="160" cy="30" rx="50" ry="8" fill="#ffffff" stroke="#94a3b8" stroke-width="2"/>

    
    
    
    <line x1="110" y1="50" x2="132" y2="50" stroke="#1e2945" stroke-width="2.5"/>
    <text x="102" y="55" font-size="13" font-weight="700" text-anchor="end" fill="#1e2945">30</text>
    
    
    <line x1="110" y1="74" x2="122" y2="74" stroke="#475569" stroke-width="1.5"/>
    
    <line x1="110" y1="98" x2="122" y2="98" stroke="#475569" stroke-width="1.5"/>
    
    <line x1="110" y1="122" x2="122" y2="122" stroke="#475569" stroke-width="1.5"/>
    
    <line x1="110" y1="146" x2="125" y2="146" stroke="#475569" stroke-width="2"/>
    <text x="102" y="150" font-size="11" font-weight="600" text-anchor="end" fill="#64748b">26</text>

    
    <line x1="110" y1="190" x2="132" y2="190" stroke="#1e2945" stroke-width="2.5"/>
    <text x="102" y="195" font-size="13" font-weight="700" text-anchor="end" fill="#1e2945">25</text>
    
    
    <line x1="110" y1="214" x2="125" y2="214" stroke="#475569" stroke-width="2"/>
    <text x="102" y="218" font-size="11" font-weight="600" text-anchor="end" fill="#64748b">24</text>
    
    <line x1="110" y1="238" x2="122" y2="238" stroke="#475569" stroke-width="1.5"/>
    
    <line x1="110" y1="262" x2="122" y2="262" stroke="#475569" stroke-width="1.5"/>
    
    <line x1="110" y1="286" x2="122" y2="286" stroke="#475569" stroke-width="1.5"/>

    
    <line x1="110" y1="310" x2="132" y2="310" stroke="#1e2945" stroke-width="2.5"/>
    <text x="102" y="315" font-size="13" font-weight="700" text-anchor="end" fill="#1e2945">20</text>

    <text x="75" y="25" font-size="12" font-weight="700" fill="#64748b">mL</text>

    
    <path d="M 160 215 L 160 235" stroke="#0284c7" stroke-width="1.5"/>
    <circle cx="160" cy="190" r="3.5" fill="#0284c7"/>
    <text x="160" y="250" font-size="12" font-weight="700" text-anchor="middle" fill="#0369a1">Meniscus</text>
    <text x="160" y="264" font-size="11" text-anchor="middle" fill="#64748b">(bottom)</text>

    

    
    <g id="sight-high" class="sightline" onclick="setMode('high')">
      
      <line x1="410" y1="80" x2="110" y2="141.2" stroke="#dc2626" stroke-width="2.5" stroke-dasharray="5 4"/>
      
      <circle cx="110" cy="141.2" r="4.5" fill="#dc2626"/>
      
      
      <g class="eye-group" transform="translate(415, 68)">
        <path d="M 0 12 Q 18 -4, 36 12 Q 18 28, 0 12 Z" fill="#ffffff" stroke="#dc2626" stroke-width="2"/>
        <circle cx="18" cy="12" r="6.5" fill="#dc2626"/>
        <circle cx="16" cy="10" r="2" fill="#ffffff"/>
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      <rect x="458" y="65" width="76" height="30" rx="6" fill="#fee2e2" stroke="#ef4444" stroke-width="1.5"/>
      <text x="496" y="78" font-size="11" font-weight="800" text-anchor="middle" fill="#b91c1c">TOO HIGH</text>
      <text x="496" y="91" font-size="10.5" font-weight="600" text-anchor="middle" fill="#dc2626">26.2 mL</text>
    </g>

    
    <g id="sight-center" class="sightline" onclick="setMode('center')">
      
      <line x1="410" y1="190" x2="110" y2="190" stroke="#16a34a" stroke-width="2.5" stroke-dasharray="5 4"/>
      
      <circle cx="160" cy="190" r="5" fill="#16a34a"/>
      <circle cx="110" cy="190" r="4.5" fill="#16a34a"/>
      
      
      <g class="eye-group" transform="translate(415, 178)">
        <path d="M 0 12 Q 18 -4, 36 12 Q 18 28, 0 12 Z" fill="#ffffff" stroke="#16a34a" stroke-width="2.5"/>
        <circle cx="18" cy="12" r="6.5" fill="#16a34a"/>
        <circle cx="16" cy="10" r="2" fill="#ffffff"/>
      </g>

      
      <rect x="458" y="174" width="76" height="32" rx="6" fill="#dcfce7" stroke="#22c55e" stroke-width="1.5"/>
      <text x="496" y="188" font-size="11" font-weight="800" text-anchor="middle" fill="#15803d">✓ CORRECT</text>
      <text x="496" y="201" font-size="11" font-weight="700" text-anchor="middle" fill="#16a34a">25.0 mL</text>
    </g>

    
    <g id="sight-low" class="sightline" onclick="setMode('low')">
      
      <line x1="410" y1="300" x2="110" y2="209.2" stroke="#dc2626" stroke-width="2.5" stroke-dasharray="5 4"/>
      
      <circle cx="110" cy="209.2" r="4.5" fill="#dc2626"/>

      
      <g class="eye-group" transform="translate(415, 288)">
        <path d="M 0 12 Q 18 -4, 36 12 Q 18 28, 0 12 Z" fill="#ffffff" stroke="#dc2626" stroke-width="2"/>
        <circle cx="18" cy="12" r="6.5" fill="#dc2626"/>
        <circle cx="16" cy="10" r="2" fill="#ffffff"/>
      </g>

      
      <rect x="458" y="285" width="76" height="30" rx="6" fill="#fee2e2" stroke="#ef4444" stroke-width="1.5"/>
      <text x="496" y="298" font-size="11" font-weight="800" text-anchor="middle" fill="#b91c1c">TOO LOW</text>
      <text x="496" y="311" font-size="10.5" font-weight="600" text-anchor="middle" fill="#dc2626">24.2 mL</text>
    </g>
  </svg>
</div>

<script>
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      center: document.getElementById('sight-center'),
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        } else {
          lines[key].classList.add('dimmed');
        }
      });
    }
  }
</script>

</body>
</html>

Reading Analogue Scales and Avoiding Parallax Error

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      width: 100%;
      background: transparent;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      padding: 6px 4px;
    }
    .grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
      gap: 16px;
      width: 100%;
      max-width: 680px;
      margin: 0 auto;
    }
    .column {
      display: flex;
      flex-direction: column;
      align-items: center;
    }
    .badge {
      font-size: 13px;
      font-weight: 700;
      padding: 5px 12px;
      border-radius: 9999px;
      margin-bottom: 6px;
      letter-spacing: 0.2px;
      text-align: center;
    }
    .badge-error {
      background: #fee2e2;
      color: #dc2626;
    }
    .badge-correct {
      background: #dcfce7;
      color: #16a34a;
    }
    svg {
      width: 100%;
      height: auto;
      max-width: 320px;
      display: block;
    }
    .note {
      font-size: 12.5px;
      font-weight: 600;
      text-align: center;
      margin-top: 4px;
      line-height: 1.35;
      padding: 0 4px;
    }
    .note-error {
      color: #b91c1c;
    }
    .note-correct {
      color: #15803d;
    }
  </style>
</head>
<body>
  <div class="grid">
    
    <div class="column">
      <div class="badge badge-error">❌ Angled View — Parallax Error</div>
      <svg viewBox="0 0 320 255" aria-label="Ammeter reading with parallax error">
        <defs>
          <linearGradient id="mirrorGrad1" x1="0%" y1="0%" x2="100%" y2="0%">
            <stop offset="0%" stop-color="#cbd5e1" />
            <stop offset="50%" stop-color="#f8fafc" />
            <stop offset="100%" stop-color="#cbd5e1" />
          </linearGradient>
          <filter id="shadow1" x="-10%" y="-10%" width="120%" height="120%">
            <feDropShadow dx="1" dy="2" stdDeviation="1.5" flood-opacity="0.15" />
          </filter>
        </defs>

        
        <path d="M 30 205 A 130 130 0 0 1 290 205 L 270 215 A 110 110 0 0 0 50 215 Z" fill="#f1f5f9" stroke="#cbd5e1" stroke-width="1"/>
        
        
        <path d="M 63.3 142.3 A 118 118 0 0 1 256.7 142.3 L 241.9 152.6 A 100 100 0 0 0 78.1 152.6 Z" fill="url(#mirrorGrad1)" stroke="#94a3b8" stroke-width="0.8"/>
        <text x="160" y="152" font-size="8" fill="#64748b" font-weight="600" text-anchor="middle" letter-spacing="1">MIRROR STRIP</text>

        
        <path d="M 53.5 135.5 A 130 130 0 0 1 266.5 135.5" fill="none" stroke="#334155" stroke-width="1.5"/>

        
        
        <line x1="53.5" y1="135.5" x2="43.6" y2="128.6" stroke="#1e2945" stroke-width="2"/>
        <text x="36" y="125" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">0</text>
        
        
        <line x1="89.2" y1="100.9" x2="82.9" y2="90.9" stroke="#1e2945" stroke-width="2"/>
        <text x="76" y="84" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">1</text>
        
        
        <line x1="135.2" y1="82.4" x2="131.4" y2="70.6" stroke="#1e2945" stroke-width="2"/>
        <text x="128" y="63" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">2</text>
        
        
        <line x1="184.8" y1="82.4" x2="188.6" y2="70.6" stroke="#1e2945" stroke-width="2"/>
        <text x="192" y="63" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">3</text>
        
        
        <line x1="230.8" y1="100.9" x2="237.1" y2="90.9" stroke="#1e2945" stroke-width="2"/>
        <text x="244" y="84" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">4</text>
        
        
        <line x1="266.5" y1="135.5" x2="276.4" y2="128.6" stroke="#1e2945" stroke-width="2"/>
        <text x="284" y="125" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">5</text>

        
        <line x1="70.6" y1="117.0" x2="65.3" y2="111.7" stroke="#64748b" stroke-width="1.2"/>
        <line x1="111.4" y1="90.4" x2="108.5" y2="83.3" stroke="#64748b" stroke-width="1.2"/>
        <line x1="160.0" y1="80.0" x2="160.0" y2="72.0" stroke="#64748b" stroke-width="1.2"/>
        <line x1="208.6" y1="90.4" x2="211.5" y2="83.3" stroke="#64748b" stroke-width="1.2"/>
        <line x1="249.4" y1="117.0" x2="254.7" y2="111.7" stroke="#64748b" stroke-width="1.2"/>

        
        <text x="160" y="112" font-size="14" font-weight="800" fill="#2563eb" text-anchor="middle">A</text>

        
        <g transform="translate(240, 14)">
          <text x="16" y="-3" font-size="10" font-weight="700" fill="#dc2626" text-anchor="middle">Angled Eye</text>
          <path d="M 0 14 Q 16 0 32 14 Q 16 28 0 14 Z" fill="#ffffff" stroke="#1e2945" stroke-width="1.8"/>
          <circle cx="16" cy="14" r="6" fill="#3b82f6"/>
          <circle cx="16" cy="14" r="2.8" fill="#0f172a"/>
          <circle cx="14.5" cy="12.5" r="1.2" fill="#ffffff"/>
        </g>

        
        <line x1="256" y1="28" x2="148" y2="112.5" stroke="#dc2626" stroke-width="1.5" stroke-dasharray="4 3"/>

        
        <line x1="160" y1="210" x2="173.5" y2="96" stroke="#94a3b8" stroke-width="2.5" stroke-dasharray="3 2"/>

        
        <line x1="160" y1="210" x2="196" y2="75" stroke="#dc2626" stroke-width="3" stroke-linecap="round" filter="url(#shadow1)"/>
        <circle cx="160" cy="210" r="6" fill="#1e2945"/>
        <circle cx="160" cy="210" r="2.5" fill="#ffffff"/>

        
        
        <path d="M 108 123 L 168 120" fill="none" stroke="#64748b" stroke-width="1.2"/>
        <circle cx="168" cy="120" r="2" fill="#64748b"/>
        <text x="104" y="126" font-size="9.5" font-weight="700" fill="#64748b" text-anchor="end">Mirror reflection</text>

        
        <path d="M 235 60 L 198 73" fill="none" stroke="#dc2626" stroke-width="1.2"/>
        <circle cx="198" cy="73" r="2" fill="#dc2626"/>
        <text x="238" y="63" font-size="9.5" font-weight="700" fill="#dc2626" text-anchor="start">Physical needle</text>

        
        <rect x="135" y="222" width="138" height="20" rx="4" fill="#fee2e2" stroke="#fca5a5" stroke-width="1"/>
        <text x="204" y="236" font-size="10" font-weight="700" fill="#991b1b" text-anchor="middle">Apparent: 3.2 A (Wrong)</text>
      </svg>
      <div class="note note-error">Reflection visible beside needle = reading is skewed</div>
    </div>

    
    <div class="column">
      <div class="badge badge-correct">✓ Perpendicular View — Accurate</div>
      <svg viewBox="0 0 320 255" aria-label="Ammeter reading with correct perpendicular alignment">
        <defs>
          <linearGradient id="mirrorGrad2" x1="0%" y1="0%" x2="100%" y2="0%">
            <stop offset="0%" stop-color="#cbd5e1" />
            <stop offset="50%" stop-color="#f8fafc" />
            <stop offset="100%" stop-color="#cbd5e1" />
          </linearGradient>
        </defs>

        
        <path d="M 30 205 A 130 130 0 0 1 290 205 L 270 215 A 110 110 0 0 0 50 215 Z" fill="#f1f5f9" stroke="#cbd5e1" stroke-width="1"/>
        
        
        <path d="M 63.3 142.3 A 118 118 0 0 1 256.7 142.3 L 241.9 152.6 A 100 100 0 0 0 78.1 152.6 Z" fill="url(#mirrorGrad2)" stroke="#94a3b8" stroke-width="0.8"/>
        <text x="160" y="152" font-size="8" fill="#64748b" font-weight="600" text-anchor="middle" letter-spacing="1">MIRROR STRIP</text>

        
        <path d="M 53.5 135.5 A 130 130 0 0 1 266.5 135.5" fill="none" stroke="#334155" stroke-width="1.5"/>

        
        
        <line x1="53.5" y1="135.5" x2="43.6" y2="128.6" stroke="#1e2945" stroke-width="2"/>
        <text x="36" y="125" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">0</text>
        
        
        <line x1="89.2" y1="100.9" x2="82.9" y2="90.9" stroke="#1e2945" stroke-width="2"/>
        <text x="76" y="84" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">1</text>
        
        
        <line x1="135.2" y1="82.4" x2="131.4" y2="70.6" stroke="#1e2945" stroke-width="2"/>
        <text x="128" y="63" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">2</text>
        
        
        <line x1="184.8" y1="82.4" x2="188.6" y2="70.6" stroke="#1e2945" stroke-width="2"/>
        <text x="192" y="63" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">3</text>
        
        
        <line x1="230.8" y1="100.9" x2="237.1" y2="90.9" stroke="#1e2945" stroke-width="2"/>
        <text x="244" y="84" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">4</text>
        
        
        <line x1="266.5" y1="135.5" x2="276.4" y2="128.6" stroke="#1e2945" stroke-width="2"/>
        <text x="284" y="125" font-size="12" font-weight="700" fill="#1e2945" text-anchor="middle">5</text>

        
        <line x1="70.6" y1="117.0" x2="65.3" y2="111.7" stroke="#64748b" stroke-width="1.2"/>
        <line x1="111.4" y1="90.4" x2="108.5" y2="83.3" stroke="#64748b" stroke-width="1.2"/>
        <line x1="160.0" y1="80.0" x2="160.0" y2="72.0" stroke="#64748b" stroke-width="1.2"/>
        <line x1="208.6" y1="90.4" x2="211.5" y2="83.3" stroke="#64748b" stroke-width="1.2"/>
        <line x1="249.4" y1="117.0" x2="254.7" y2="111.7" stroke="#64748b" stroke-width="1.2"/>

        
        <text x="160" y="112" font-size="14" font-weight="800" fill="#2563eb" text-anchor="middle">A</text>

        
        <g transform="translate(180, 14)">
          <text x="16" y="-3" font-size="10" font-weight="700" fill="#16a34a" text-anchor="middle">90° Eye</text>
          <path d="M 0 14 Q 16 0 32 14 Q 16 28 0 14 Z" fill="#ffffff" stroke="#1e2945" stroke-width="1.8"/>
          <circle cx="16" cy="14" r="6" fill="#16a34a"/>
          <circle cx="16" cy="14" r="2.8" fill="#0f172a"/>
          <circle cx="14.5" cy="12.5" r="1.2" fill="#ffffff"/>
        </g>

        
        <line x1="196" y1="28" x2="160" y2="210" stroke="#16a34a" stroke-width="1.5" stroke-dasharray="4 3"/>

        
        <line x1="160" y1="210" x2="187.5" y2="71" stroke="#dc2626" stroke-width="3" stroke-linecap="round"/>
        <circle cx="160" cy="210" r="6" fill="#1e2945"/>
        <circle cx="160" cy="210" r="2.5" fill="#ffffff"/>

        
        <circle cx="187.5" cy="71" r="5" fill="none" stroke="#16a34a" stroke-width="1.5"/>

        
        <path d="M 95 56 L 178 70" fill="none" stroke="#16a34a" stroke-width="1.2"/>
        <circle cx="178" cy="70" r="2" fill="#16a34a"/>
        <text x="90" y="52" font-size="9.5" font-weight="700" fill="#15803d" text-anchor="end">Reflection hidden</text>
        <text x="90" y="64" font-size="9.5" font-weight="700" fill="#15803d" text-anchor="end">behind needle</text>

        
        <rect x="135" y="222" width="138" height="20" rx="4" fill="#dcfce7" stroke="#86efac" stroke-width="1"/>
        <text x="204" y="236" font-size="10" font-weight="700" fill="#166534" text-anchor="middle">True Reading: 3.0 A ✓</text>
      </svg>
      <div class="note note-correct">Needle covers reflection = line of sight is 90° to scale</div>
    </div>
  </div>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 12px 16px;
      user-select: none;
    }

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

    .tab-btn {
      flex: 1;
      min-width: 90px;
      padding: 7px 10px;
      font-size: 13px;
      font-weight: 600;
      border-radius: 8px;
      border: 1px solid #e2e8f0;
      background: #f8fafc;
      color: #64748b;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 4px;
      transition: all 0.2s ease;
      box-shadow: 0 1px 2px rgba(0,0,0,0.03);
    }
    .tab-btn:hover {
      background: #f1f5f9;
      color: #1e2945;
    }
    .tab-btn.active {
      background: #ffffff;
      color: #0f172a;
      border-color: #cbd5e1;
      box-shadow: 0 2px 5px rgba(0,0,0,0.08);
    }
    .tab-btn.btn-b.active {
      border-color: #16a34a;
      color: #15803d;
      background: #f0fdf4;
    }

    .svg-container {
      width: 100%;
      max-width: 520px;
      aspect-ratio: 500 / 300;
      position: relative;
    }

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

    .sightline {
      transition: stroke-dashoffset 0.3s ease, opacity 0.3s ease;
      stroke-dasharray: 6 4;
    }

    .eye-group {
      cursor: pointer;
      transition: transform 0.2s ease, opacity 0.2s ease;
    }
    .eye-group:hover {
      opacity: 0.85;
    }

    .readout-card {
      display: flex;
      gap: 12px;
      justify-content: center;
      align-items: center;
      width: 100%;
      max-width: 460px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 14px;
      margin-top: 4px;
      font-size: 13px;
    }

    .readout-item {
      display: flex;
      align-items: center;
      gap: 6px;
      font-weight: 600;
      color: #64748b;
      opacity: 0.45;
      transition: opacity 0.2s ease, transform 0.2s ease;
    }
    .readout-item.active {
      opacity: 1;
      transform: scale(1.04);
    }
    .tag-err { color: #dc2626; }
    .tag-ok { color: #16a34a; font-weight: 700; }
  </style>
</head>
<body>

  <div class="controls">
    <button class="tab-btn" data-view="A">👁️ A (Left)</button>
    <button class="tab-btn btn-b active" data-view="B">👁️ B (90° ✓)</button>
    <button class="tab-btn" data-view="C">👁️ C (Right)</button>
    <button class="tab-btn" data-view="all">Show All</button>
  </div>

  <div class="svg-container">
    <svg viewBox="0 0 500 290">
      <defs>
        
        <filter id="shadow" x="-10%" y="-10%" width="130%" height="130%">
          <feDropShadow dx="0" dy="2" stdDeviation="2" flood-opacity="0.12" />
        </filter>
        <marker id="arrow-green" markerWidth="6" markerHeight="6" refX="4" refY="3" orient="auto">
          <polygon points="0 1, 4 3, 0 5" fill="#16a34a" />
        </marker>
        <marker id="arrow-red" markerWidth="6" markerHeight="6" refX="4" refY="3" orient="auto">
          <polygon points="0 1, 4 3, 0 5" fill="#dc2626" />
        </marker>
      </defs>

      
      <rect x="30" y="220" width="440" height="42" rx="6" fill="#f1f5f9" stroke="#cbd5e1" stroke-width="1.5" />
      <line x1="40" y1="220" x2="460" y2="220" stroke="#334155" stroke-width="2" />

      
      
      

      
      
      <line x1="50" y1="220" x2="50" y2="238" stroke="#334155" stroke-width="2" />
      <text x="50" y="252" text-anchor="middle" font-size="12" font-weight="600" fill="#475569">4.0</text>
      
      <line x1="70" y1="220" x2="70" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="90" y1="220" x2="90" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="110" y1="220" x2="110" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="130" y1="220" x2="130" y2="230" stroke="#64748b" stroke-width="1" />
      
      
      <line x1="150" y1="220" x2="150" y2="235" stroke="#334155" stroke-width="1.5" />
      <text x="150" y="252" text-anchor="middle" font-size="12" font-weight="600" fill="#475569">4.5</text>
      
      <line x1="170" y1="220" x2="170" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="190" y1="220" x2="190" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="210" y1="220" x2="210" y2="234" stroke="#dc2626" stroke-width="2" id="tick-48" />
      <line x1="230" y1="220" x2="230" y2="230" stroke="#64748b" stroke-width="1" />

      
      <line x1="250" y1="220" x2="250" y2="238" stroke="#16a34a" stroke-width="2.5" id="tick-50" />
      <text x="250" y="252" text-anchor="middle" font-size="13" font-weight="700" fill="#16a34a">5.0</text>

      
      <line x1="270" y1="220" x2="270" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="290" y1="220" x2="290" y2="234" stroke="#dc2626" stroke-width="2" id="tick-52" />
      <line x1="310" y1="220" x2="310" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="330" y1="220" x2="330" y2="230" stroke="#64748b" stroke-width="1" />

      
      <line x1="350" y1="220" x2="350" y2="235" stroke="#334155" stroke-width="1.5" />
      <text x="350" y="252" text-anchor="middle" font-size="12" font-weight="600" fill="#475569">5.5</text>
      
      <line x1="370" y1="220" x2="370" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="390" y1="220" x2="390" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="410" y1="220" x2="410" y2="230" stroke="#64748b" stroke-width="1" />
      <line x1="430" y1="220" x2="430" y2="230" stroke="#64748b" stroke-width="1" />

      
      <line x1="450" y1="220" x2="450" y2="238" stroke="#334155" stroke-width="2" />
      <text x="450" y="252" text-anchor="middle" font-size="12" font-weight="600" fill="#475569">6.0</text>

      
      <line x1="262" y1="165" x2="262" y2="218" stroke="#94a3b8" stroke-width="1.2" stroke-dasharray="2 2" />
      <line x1="259" y1="165" x2="265" y2="165" stroke="#94a3b8" stroke-width="1.2" />
      <line x1="259" y1="218" x2="265" y2="218" stroke="#94a3b8" stroke-width="1.2" />
      <text x="270" y="195" font-size="11" font-weight="600" fill="#64748b">Gap</text>

      
      
      

      
      <g id="line-group-A">
        <line class="sightline" x1="170" y1="55" x2="290" y2="220" stroke="#dc2626" stroke-width="2.5" />
        <circle cx="290" cy="220" r="4" fill="#dc2626" />
        
        <g transform="translate(290, 275)">
          <rect x="-18" y="-12" width="36" height="18" rx="4" fill="#fee2e2" stroke="#ef4444" stroke-width="1"/>
          <text x="0" y="1" text-anchor="middle" dominant-baseline="middle" font-size="11" font-weight="700" fill="#b91c1c">5.2</text>
        </g>
      </g>

      <g id="line-group-C">
        <line class="sightline" x1="330" y1="55" x2="210" y2="220" stroke="#dc2626" stroke-width="2.5" />
        <circle cx="210" cy="220" r="4" fill="#dc2626" />
        
        <g transform="translate(210, 275)">
          <rect x="-18" y="-12" width="36" height="18" rx="4" fill="#fee2e2" stroke="#ef4444" stroke-width="1"/>
          <text x="0" y="1" text-anchor="middle" dominant-baseline="middle" font-size="11" font-weight="700" fill="#b91c1c">4.8</text>
        </g>
      </g>

      <g id="line-group-B">
        <line class="sightline" x1="250" y1="55" x2="250" y2="220" stroke="#16a34a" stroke-width="3" />
        <circle cx="250" cy="220" r="5" fill="#16a34a" />
        
        <g transform="translate(250, 275)">
          <rect x="-24" y="-12" width="48" height="18" rx="4" fill="#dcfce7" stroke="#22c55e" stroke-width="1"/>
          <text x="0" y="1" text-anchor="middle" dominant-baseline="middle" font-size="11" font-weight="700" fill="#15803d">5.0 ✓</text>
        </g>
      </g>

      
      <g filter="url(#shadow)">
        
        <polygon points="247,105 253,105 251,165 249,165" fill="#ea580c" />
        <circle cx="250" cy="105" r="7" fill="#c2410c" />
        <circle cx="250" cy="105" r="3" fill="#ffffff" />
        
        <circle cx="250" cy="165" r="3.5" fill="#dc2626" stroke="#ffffff" stroke-width="1.5" />
        <text x="250" y="125" text-anchor="middle" font-size="11" font-weight="700" fill="#c2410c" transform="rotate(-90 250 125)">POINTER</text>
      </g>

      
      <g id="eye-A" class="eye-group" transform="translate(170, 45)">
        <circle cx="0" cy="0" r="16" fill="#fef2f2" stroke="#dc2626" stroke-width="1.5" />
        <text x="0" y="5" text-anchor="middle" font-size="16">👁️</text>
        <text x="0" y="-21" text-anchor="middle" font-size="12" font-weight="700" fill="#dc2626">A (Left)</text>
      </g>

      
      <g id="eye-B" class="eye-group" transform="translate(250, 45)">
        <circle cx="0" cy="0" r="18" fill="#f0fdf4" stroke="#16a34a" stroke-width="2" />
        <text x="0" y="5" text-anchor="middle" font-size="18">👁️</text>
        <text x="0" y="-23" text-anchor="middle" font-size="12" font-weight="700" fill="#16a34a">B (90°)</text>
      </g>

      
      <g id="eye-C" class="eye-group" transform="translate(330, 45)">
        <circle cx="0" cy="0" r="16" fill="#fef2f2" stroke="#dc2626" stroke-width="1.5" />
        <text x="0" y="5" text-anchor="middle" font-size="16">👁️</text>
        <text x="0" y="-21" text-anchor="middle" font-size="12" font-weight="700" fill="#dc2626">C (Right)</text>
      </g>
    </svg>
  </div>

  <div class="readout-card">
    <div id="read-A" class="readout-item tag-err"><span>A:</span> <span>5.2</span> (Too high)</div>
    <div id="read-B" class="readout-item tag-ok active"><span>B:</span> <span>5.0</span> (Correct ✓)</div>
    <div id="read-C" class="readout-item tag-err"><span>C:</span> <span>4.8</span> (Too low)</div>
  </div>

  <script src="{{VENDOR_CDN}}/classace-diagram.js"></script>
  <script>
    const lineA = document.getElementById('line-group-A');
    const lineB = document.getElementById('line-group-B');
    const lineC = document.getElementById('line-group-C');

    const readA = document.getElementById('read-A');
    const readB = document.getElementById('read-B');
    const readC = document.getElementById('read-C');

    const buttons = document.querySelectorAll('.tab-btn');

    function setView(view) {
      buttons.forEach(b => b.classList.toggle('active', b.dataset.view === view));

      const showA = view === 'A' || view === 'all';
      const showB = view === 'B' || view === 'all';
      const showC = view === 'C' || view === 'all';

      lineA.style.opacity = showA ? '1' : '0.08';
      lineB.style.opacity = showB ? '1' : '0.08';
      lineC.style.opacity = showC ? '1' : '0.08';

      readA.classList.toggle('active', showA);
      readB.classList.toggle('active', showB);
      readC.classList.toggle('active', showC);
    }

    buttons.forEach(btn => {
      onTap(btn, () => setView(btn.dataset.view));
    });

    onTap(document.getElementById('eye-A'), () => setView('A'));
    onTap(document.getElementById('eye-B'), () => setView('B'));
    onTap(document.getElementById('eye-C'), () => setView('C'));

    // Initialize state
    setView('B');
  </script>
</body>
</html>

UK-GCSE-SCIENCE-WS-2-06

Aligned learning resources

Related diagrams