<!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="5:4">
  <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;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 8px;
    }
    .graph-wrapper {
      width: 100%;
      max-width: 500px;
      position: relative;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }
    .grid-line {
      stroke: #e2e8f0;
      stroke-width: 1;
    }
    .axis {
      stroke: #94a3b8;
      stroke-width: 1.75;
      stroke-linecap: round;
    }
    .axis-label {
      fill: #64748b;
      font-size: 11px;
      font-weight: 500;
      text-anchor: middle;
      dominant-baseline: middle;
    }
    .line-fn {
      stroke: #1e2945;
      stroke-width: 3.5;
      stroke-linecap: round;
    }
    .callout-bg {
      filter: drop-shadow(0 2px 6px rgba(0, 0, 0, 0.08));
    }
    .point-pulse {
      animation: pulse 2.5s infinite ease-in-out;
    }
    @keyframes pulse {
      0%, 100% { transform: scale(1); opacity: 0.25; }
      50% { transform: scale(1.6); opacity: 0; }
    }
  </style>
</head>
<body>
  <div class="graph-wrapper">
    <svg viewBox="0 0 500 400">
      <defs>
        <marker id="arrow-x" viewBox="0 0 10 10" refX="6" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1.5 L 8 5 L 0 8.5 z" fill="#94a3b8" />
        </marker>
        <marker id="arrow-y" viewBox="0 0 10 10" refX="5" refY="4" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 1.5 8 L 5 0 L 8.5 8 z" fill="#94a3b8" />
        </marker>
      </defs>

      
      <line x1="82" y1="25" x2="82" y2="375" class="grid-line" />
      <line x1="193" y1="25" x2="193" y2="375" class="grid-line" />
      <line x1="304" y1="25" x2="304" y2="375" class="grid-line" />
      <line x1="415" y1="25" x2="415" y2="375" class="grid-line" />

      
      <line x1="40" y1="360" x2="460" y2="360" class="grid-line" />
      <line x1="40" y1="322" x2="460" y2="322" class="grid-line" />
      <line x1="40" y1="283" x2="460" y2="283" class="grid-line" />
      <line x1="40" y1="244" x2="460" y2="244" class="grid-line" />
      <line x1="40" y1="205" x2="460" y2="205" class="grid-line" />
      <line x1="40" y1="166" x2="460" y2="166" class="grid-line" />
      <line x1="40" y1="127" x2="460" y2="127" class="grid-line" />
      <line x1="40" y1="88" x2="460" y2="88" class="grid-line" />
      <line x1="40" y1="49" x2="460" y2="49" class="grid-line" />

      
      
      <line x1="45" y1="322" x2="465" y2="322" class="axis" marker-end="url(#arrow-x)" />
      
      <line x1="82" y1="375" x2="82" y2="20" class="axis" marker-end="url(#arrow-y)" />

      
      <text x="82" y="337" class="axis-label">0</text>
      <text x="193" y="337" class="axis-label">1</text>
      <text x="304" y="337" class="axis-label">2</text>
      <text x="415" y="337" class="axis-label">3</text>
      <text x="475" y="322" class="axis-label" style="font-weight:700; fill:#475569;">x</text>

      <text x="68" y="283" class="axis-label">1</text>
      <text x="68" y="244" class="axis-label">2</text>
      <text x="68" y="205" class="axis-label">3</text>
      <text x="68" y="166" class="axis-label">4</text>
      <text x="68" y="127" class="axis-label">5</text>
      <text x="68" y="88" class="axis-label">6</text>
      <text x="68" y="49" class="axis-label">7</text>
      <text x="82" y="12" class="axis-label" style="font-weight:700; fill:#475569;">y</text>

      
      
      <line x1="104" y1="376" x2="424" y2="40" class="line-fn" />

      
      <g transform="translate(370, 75)">
        <rect x="-42" y="-12" width="84" height="24" rx="6" fill="#1e2945" />
        <text x="0" y="4" fill="#ffffff" font-size="12" font-weight="700" text-anchor="middle">y = 3x − 2</text>
      </g>

      
      
      <line x1="193" y1="127" x2="193" y2="322" stroke="#ef4444" stroke-width="1.2" stroke-dasharray="3,3" opacity="0.6" />
      <line x1="193" y1="127" x2="82" y2="127" stroke="#ef4444" stroke-width="1.2" stroke-dasharray="3,3" opacity="0.6" />

      
      <g class="callout-bg" transform="translate(10, 42)">
        
        <path d="M 170 30 L 193 85" stroke="#ef4444" stroke-width="1.5" fill="none" stroke-dasharray="2,2" />
        
        <rect x="0" y="0" width="176" height="54" rx="8" fill="#ffffff" stroke="#fecaca" stroke-width="1.5" />
        
        
        <circle cx="18" cy="27" r="10" fill="#dc2626" />
        <text x="18" y="31" fill="#ffffff" font-size="12" font-weight="900" text-anchor="middle">✕</text>
        
        <text x="36" y="21" fill="#1e2945" font-size="12" font-weight="700">Point (1, 5)</text>
        <text x="36" y="35" fill="#64748b" font-size="11" font-weight="600">3(1) − 2 = 1 ≠ 5</text>
        <text x="36" y="48" fill="#dc2626" font-size="10.5" font-weight="800">FALSE → Off Graph</text>
      </g>

      
      <circle cx="193" cy="127" r="12" fill="#ef4444" class="point-pulse" style="transform-origin: 193px 127px;" />
      
      <circle cx="193" cy="127" r="6.5" fill="#dc2626" stroke="#ffffff" stroke-width="2.5" />

      
      
      <line x1="304" y1="166" x2="304" y2="322" stroke="#16a34a" stroke-width="1.2" stroke-dasharray="3,3" opacity="0.6" />
      <line x1="304" y1="166" x2="82" y2="166" stroke="#16a34a" stroke-width="1.2" stroke-dasharray="3,3" opacity="0.6" />

      
      <g class="callout-bg" transform="translate(315, 205)">
        
        <path d="M 25 0 L -11 -39" stroke="#16a34a" stroke-width="1.5" fill="none" stroke-dasharray="2,2" />

        <rect x="0" y="0" width="175" height="54" rx="8" fill="#ffffff" stroke="#bbf7d0" stroke-width="1.5" />
        
        
        <circle cx="18" cy="27" r="10" fill="#16a34a" />
        <text x="18" y="31" fill="#ffffff" font-size="12" font-weight="900" text-anchor="middle">✓</text>
        
        <text x="36" y="21" fill="#1e2945" font-size="12" font-weight="700">Point (2, 4)</text>
        <text x="36" y="35" fill="#64748b" font-size="11" font-weight="600">3(2) − 2 = 4</text>
        <text x="36" y="48" fill="#16a34a" font-size="10.5" font-weight="800">TRUE → On Graph</text>
      </g>

      
      <circle cx="304" cy="166" r="12" fill="#22c55e" class="point-pulse" style="transform-origin: 304px 166px;" />
      
      <circle cx="304" cy="166" r="6.5" fill="#16a34a" stroke="#ffffff" stroke-width="2.5" />
    </svg>
  </div>
</body>
</html>

Understanding That Graphs Are Sets of All Solutions

<!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%;
      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: 12px 16px 16px;
      user-select: none;
    }

    .header-bar {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      max-width: 580px;
      margin-bottom: 4px;
    }

    .badge {
      background: #eff6ff;
      border: 1px solid #bfdbfe;
      color: #1d4ed8;
      font-size: 14px;
      font-weight: 700;
      padding: 4px 12px;
      border-radius: 9999px;
      letter-spacing: 0.2px;
    }

    .subtitle {
      font-size: 13px;
      color: #64748b;
      font-weight: 600;
    }

    .svg-container {
      width: 100%;
      max-width: 580px;
      flex: 1;
      min-height: 250px;
      position: relative;
    }

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

    .controls {
      display: flex;
      gap: 8px;
      width: 100%;
      max-width: 580px;
      justify-content: center;
      margin-top: 6px;
    }

    .btn-step {
      flex: 1;
      padding: 6px 8px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 4px;
      transition: all 0.2s ease;
    }

    .btn-step.active {
      background: #ecfdf5;
      border-color: #10b981;
      color: #047857;
      box-shadow: 0 0 0 2px rgba(16, 185, 129, 0.15);
    }

    .tick {
      color: #10b981;
      font-weight: 800;
    }

    /* SVG point transitions */
    .zoom-pt {
      transition: transform 0.25s ease, opacity 0.25s ease;
      cursor: pointer;
    }

    .pulse-ring {
      animation: pulse 2s infinite ease-out;
      transform-origin: center;
    }

    @keyframes pulse {
      0% { r: 6px; opacity: 0.8; }
      100% { r: 15px; opacity: 0; }
    }
  </style>
</head>
<body>

  <div class="header-bar">
    <span class="badge">y = x² − 3</span>
    <span class="subtitle">Every point on the line is a solution</span>
  </div>

  <div class="svg-container">
    <svg viewBox="0 0 540 280">
      <defs>
        
        <clipPath id="lens-clip">
          <circle cx="395" cy="140" r="95" />
        </clipPath>
        
        <filter id="lens-shadow" x="-20%" y="-20%" width="140%" height="140%">
          <feDropShadow dx="0" dy="4" stdDeviation="6" flood-color="#0f172a" flood-opacity="0.1" />
        </filter>
      </defs>

      
      <g id="main-graph">
        
        
        
        
        <g stroke="#f1f5f9" stroke-width="1.2">
          
          <line x1="20" y1="261" x2="220" y2="261" /> 
          <line x1="20" y1="195" x2="220" y2="195" stroke="#cbd5e1" stroke-width="1.5"/> 
          <line x1="20" y1="129" x2="220" y2="129" /> 
          <line x1="20" y1="63" x2="220" y2="63" />   
          
          <line x1="47" y1="30" x2="47" y2="270" />  
          <line x1="85" y1="30" x2="85" y2="270" stroke="#cbd5e1" stroke-width="1.5"/> 
          <line x1="123" y1="30" x2="123" y2="270" /> 
          <line x1="161" y1="30" x2="161" y2="270" /> 
          <line x1="199" y1="30" x2="199" y2="270" /> 
        </g>

        
        <g fill="#94a3b8" font-size="10" font-weight="600" text-anchor="middle">
          <text x="47" y="209">-1</text>
          <text x="123" y="209">1</text>
          <text x="161" y="209">2</text>
          <text x="199" y="209">3</text>
          <text x="75" y="265" text-anchor="end">-3</text>
          <text x="75" y="133" text-anchor="end">3</text>
          <text x="75" y="67" text-anchor="end">6</text>
          <text x="215" y="190" fill="#64748b">x</text>
          <text x="85" y="24" fill="#64748b">y</text>
        </g>

        
        
        <path d="M 9,144 
                 Q 30,225 85,261 
                 T 161,173 
                 Q 185,110 203,63" 
              fill="none" stroke="#2563eb" stroke-width="3" stroke-linecap="round" />

        
        <g id="main-pts">
          
          <circle cx="85" cy="261" r="4.5" fill="#1e2945" />
          <text x="85" y="275" font-size="10" font-weight="700" fill="#1e2945" text-anchor="middle">(0, -3)</text>

          
          <circle cx="123" cy="239" r="4.5" fill="#1e2945" />
          <text x="136" y="246" font-size="10" font-weight="700" fill="#1e2945">(1, -2)</text>

          
          <circle cx="161" cy="173" r="4.5" fill="#1e2945" />
          <text x="145" y="166" font-size="10" font-weight="700" fill="#1e2945">(2, 1)</text>
        </g>

        
        <circle cx="180" cy="125" r="22" fill="#0284c7" fill-opacity="0.1" stroke="#0284c7" stroke-width="1.5" stroke-dasharray="3 3"/>
      </g>

      
      <path d="M 197,110 L 305,65" stroke="#38bdf8" stroke-width="1.2" stroke-dasharray="3 3" opacity="0.6"/>
      <path d="M 197,140 L 320,205" stroke="#38bdf8" stroke-width="1.2" stroke-dasharray="3 3" opacity="0.6"/>

      
      <g id="zoom-callout">
        
        <circle cx="395" cy="140" r="95" fill="#ffffff" filter="url(#lens-shadow)" stroke="#0284c7" stroke-width="3"/>
        
        
        <g clip-path="url(#lens-clip)">
          
          
          <g stroke="#f1f5f9" stroke-width="1">
            
            <line x1="356" y1="40" x2="356" y2="240" />
            <line x1="382" y1="40" x2="382" y2="240" />
            <line x1="408" y1="40" x2="408" y2="240" />
            <line x1="434" y1="40" x2="434" y2="240" />
            
            <line x1="300" y1="196" x2="490" y2="196" />
            <line x1="300" y1="151" x2="490" y2="151" />
            <line x1="300" y1="106" x2="490" y2="106" />
            <line x1="300" y1="61" x2="490" y2="61" />
          </g>

          
          <g fill="#94a3b8" font-size="9" font-weight="600">
            <text x="356" y="230" text-anchor="middle">2.2</text>
            <text x="395" y="230" text-anchor="middle">2.5</text>
            <text x="434" y="230" text-anchor="middle">2.8</text>
            <text x="312" y="199">2.0</text>
            <text x="312" y="154">3.0</text>
            <text x="312" y="109">4.0</text>
            <text x="312" y="64">5.0</text>
          </g>

          
          
          <path d="M 320,258 Q 380,165 470,2" fill="none" stroke="#2563eb" stroke-width="4.5" stroke-linecap="round"/>

          
          
          <circle id="active-pulse" class="pulse-ring" cx="395" cy="140" fill="none" stroke="#10b981" stroke-width="2" />

          
          <g id="zpt-0" class="zoom-pt" onclick="selectPoint(0)">
            <circle cx="356" cy="203" r="5.5" fill="#10b981" stroke="#ffffff" stroke-width="2"/>
            <rect x="364" y="196" width="62" height="15" rx="3" fill="#ffffff" fill-opacity="0.9" />
            <text x="366" y="207" font-size="10" font-weight="700" fill="#065f46">(2.2, 1.84)</text>
          </g>

          
          <g id="zpt-1" class="zoom-pt" onclick="selectPoint(1)">
            <circle cx="395" cy="140" r="5.5" fill="#10b981" stroke="#ffffff" stroke-width="2"/>
            <rect x="325" y="132" width="62" height="15" rx="3" fill="#ffffff" fill-opacity="0.9" />
            <text x="327" y="143" font-size="10" font-weight="700" fill="#065f46">(2.5, 3.25)</text>
          </g>

          
          <g id="zpt-2" class="zoom-pt" onclick="selectPoint(2)">
            <circle cx="434" cy="68" r="5.5" fill="#10b981" stroke="#ffffff" stroke-width="2"/>
            <rect x="364" y="60" width="62" height="15" rx="3" fill="#ffffff" fill-opacity="0.9" />
            <text x="366" y="71" font-size="10" font-weight="700" fill="#065f46">(2.8, 4.84)</text>
          </g>
        </g>

        
        <circle cx="395" cy="140" r="95" fill="none" stroke="#38bdf8" stroke-width="1.5" opacity="0.7"/>
        <rect x="345" y="32" width="100" height="18" rx="9" fill="#0284c7" />
        <text x="395" y="44" font-size="10" font-weight="700" fill="#ffffff" text-anchor="middle" letter-spacing="0.5">ZOOM IN (x = 2 to 3)</text>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <button class="btn-step" id="btn-0" onclick="selectPoint(0)">
      <span>(2.2)² − 3 = 1.84</span>
      <span class="tick">✓</span>
    </button>
    <button class="btn-step active" id="btn-1" onclick="selectPoint(1)">
      <span>(2.5)² − 3 = 3.25</span>
      <span class="tick">✓</span>
    </button>
    <button class="btn-step" id="btn-2" onclick="selectPoint(2)">
      <span>(2.8)² − 3 = 4.84</span>
      <span class="tick">✓</span>
    </button>
  </div>

  <script>
    const points = [
      { cx: 356, cy: 203 },
      { cx: 395, cy: 140 },
      { cx: 434, cy: 68 }
    ];

    let activeIndex = 1;
    let autoTimer = null;

    function updateView() {
      // Update buttons
      for (let i = 0; i < 3; i++) {
        const btn = document.getElementById(`btn-${i}`);
        const pt = document.getElementById(`zpt-${i}`);
        if (i === activeIndex) {
          btn.classList.add('active');
          pt.style.opacity = '1';
        } else {
          btn.classList.remove('active');
          pt.style.opacity = '0.75';
        }
      }

      // Move pulse ring
      const pulse = document.getElementById('active-pulse');
      pulse.setAttribute('cx', points[activeIndex].cx);
      pulse.setAttribute('cy', points[activeIndex].cy);
    }

    function selectPoint(index) {
      activeIndex = index;
      updateView();
      resetTimer();
    }

    function nextPoint() {
      activeIndex = (activeIndex + 1) % points.length;
      updateView();
    }

    function resetTimer() {
      if (autoTimer) clearInterval(autoTimer);
      autoTimer = setInterval(nextPoint, 3600);
    }

    // Initialize
    updateView();
    resetTimer();
  </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="1:1">
  <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;
      width: 100%;
      height: 100%;
      padding: 12px;
      user-select: none;
    }

    .controls {
      display: flex;
      align-items: center;
      gap: 8px;
      margin-bottom: 8px;
      z-index: 10;
    }

    .step-btn {
      background: #f1f5f9;
      border: 1px solid #e2e8f0;
      color: #1e2945;
      padding: 6px 12px;
      border-radius: 20px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      transition: background 0.2s, color 0.2s, box-shadow 0.2s;
    }

    .step-btn.active {
      background: #2563eb;
      border-color: #2563eb;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(37, 99, 235, 0.3);
    }

    .play-btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      width: 32px;
      height: 32px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 12px;
      cursor: pointer;
      transition: background 0.2s;
    }

    .play-btn:active {
      background: #f1f5f9;
    }

    .graph-container {
      position: relative;
      width: 100%;
      max-width: 360px;
      aspect-ratio: 1 / 1;
      display: flex;
      align-items: center;
      justify-content: center;
    }

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

    .grid-line {
      stroke: #f1f5f9;
      stroke-width: 1;
    }

    .axis-line {
      stroke: #94a3b8;
      stroke-width: 1.5;
      stroke-linecap: round;
    }

    .axis-tick {
      font-size: 10px;
      fill: #64748b;
      font-weight: 500;
      text-anchor: middle;
      dominant-baseline: central;
    }

    /* Animated elements */
    .point-key {
      fill: #2563eb;
      stroke: #ffffff;
      stroke-width: 2;
      transition: transform 0.3s ease, opacity 0.3s ease;
      cursor: default;
    }

    .point-dense {
      fill: #38bdf8;
      stroke: #ffffff;
      stroke-width: 1.5;
      opacity: 0;
      transition: opacity 0.4s ease;
    }

    .line-solution {
      stroke: #2563eb;
      stroke-width: 3.5;
      stroke-linecap: round;
      opacity: 0;
      transition: opacity 0.5s ease;
    }

    .label-key {
      font-size: 11px;
      font-weight: 700;
      fill: #1e2945;
      transition: opacity 0.3s ease;
    }

    .label-pill {
      fill: #eff6ff;
      stroke: #bfdbfe;
      stroke-width: 1;
      rx: 4;
    }

    .caption-banner {
      opacity: 0;
      transition: opacity 0.4s ease;
    }

    .caption-text {
      font-size: 12px;
      font-weight: 700;
      fill: #1e2945;
      text-anchor: middle;
    }

    /* State visibility */
    body[data-step="1"] .point-key,
    body[data-step="1"] .label-key {
      opacity: 1;
    }

    body[data-step="2"] .point-key,
    body[data-step="2"] .point-dense {
      opacity: 1;
    }
    body[data-step="2"] .label-key {
      opacity: 0.35;
    }

    body[data-step="3"] .point-key {
      opacity: 0.6;
    }
    body[data-step="3"] .point-dense {
      opacity: 0.6;
    }
    body[data-step="3"] .line-solution {
      opacity: 1;
    }
    body[data-step="3"] .caption-banner {
      opacity: 1;
    }
  </style>
</head>
<body data-step="1">

  <div class="controls">
    <button class="step-btn active" id="btn1" onclick="setStep(1)">1. Few Points</button>
    <button class="step-btn" id="btn2" onclick="setStep(2)">2. More Points</button>
    <button class="step-btn" id="btn3" onclick="setStep(3)">3. All Solutions</button>
    <button class="play-btn" id="playToggle" onclick="togglePlay()" title="Toggle auto-play">⏸</button>
  </div>

  <div class="graph-container">
    <svg viewBox="0 0 360 360">
      <defs>
        <marker id="arrow" viewBox="0 0 6 6" refX="5" refY="3" markerWidth="4" markerHeight="4" orient="auto-start-reverse">
          <path d="M 0 0 L 6 3 L 0 6 z" fill="#94a3b8" />
        </marker>
        <filter id="shadow" x="-10%" y="-10%" width="120%" height="120%">
          <feDropShadow dx="0" dy="1" stdDeviation="2" flood-color="#000" flood-opacity="0.08"/>
        </filter>
      </defs>

      
      
      <line x1="40" y1="20" x2="40" y2="340" class="grid-line" />
      <line x1="75" y1="20" x2="75" y2="340" class="grid-line" />
      <line x1="110" y1="20" x2="110" y2="340" class="grid-line" />
      <line x1="145" y1="20" x2="145" y2="340" class="grid-line" />
      <line x1="215" y1="20" x2="215" y2="340" class="grid-line" />
      <line x1="250" y1="20" x2="250" y2="340" class="grid-line" />
      <line x1="285" y1="20" x2="285" y2="340" class="grid-line" />
      <line x1="320" y1="20" x2="320" y2="340" class="grid-line" />

      
      <line x1="20" y1="40" x2="340" y2="40" class="grid-line" />
      <line x1="20" y1="75" x2="340" y2="75" class="grid-line" />
      <line x1="20" y1="110" x2="340" y2="110" class="grid-line" />
      <line x1="20" y1="145" x2="340" y2="145" class="grid-line" />
      <line x1="20" y1="215" x2="340" y2="215" class="grid-line" />
      <line x1="20" y1="250" x2="340" y2="250" class="grid-line" />
      <line x1="20" y1="285" x2="340" y2="285" class="grid-line" />
      <line x1="20" y1="320" x2="340" y2="320" class="grid-line" />

      
      <line x1="20" y1="180" x2="340" y2="180" class="axis-line" marker-end="url(#arrow)" />
      <line x1="180" y1="340" x2="180" y2="20" class="axis-line" marker-end="url(#arrow)" />

      
      <text x="334" y="195" class="axis-tick" style="font-weight:700;">x</text>
      <text x="168" y="26" class="axis-tick" style="font-weight:700;">y</text>

      <text x="110" y="193" class="axis-tick">-2</text>
      <text x="250" y="193" class="axis-tick">2</text>
      <text x="168" y="250" class="axis-tick">-2</text>
      <text x="168" y="110" class="axis-tick">2</text>

      
      
      <line x1="127.5" y1="320" x2="267.5" y2="40" class="line-solution" />

      
      <circle cx="145" cy="285" r="4.5" class="point-dense" /> 
      <circle cx="162.5" cy="250" r="4.5" class="point-dense" /> 
      <circle cx="197.5" cy="180" r="4.5" class="point-dense" /> 
      <circle cx="232.5" cy="110" r="4.5" class="point-dense" /> 
      <circle cx="267.5" cy="40" r="4.5" class="point-dense" /> 
      <circle cx="136.25" cy="302.5" r="3.5" class="point-dense" /> 
      <circle cx="188.75" cy="197.5" r="3.5" class="point-dense" /> 
      <circle cx="223.75" cy="127.5" r="3.5" class="point-dense" /> 

      
      
      <circle cx="180" cy="215" r="6" class="point-key" />
      <g class="label-key" transform="translate(188, 206)">
        <rect x="0" y="0" width="46" height="18" class="label-pill" />
        <text x="23" y="12" text-anchor="middle" font-size="10" fill="#1e2945">(0, -1)</text>
      </g>

      
      <circle cx="215" cy="145" r="6" class="point-key" />
      <g class="label-key" transform="translate(223, 136)">
        <rect x="0" y="0" width="38" height="18" class="label-pill" />
        <text x="19" y="12" text-anchor="middle" font-size="10" fill="#1e2945">(1, 1)</text>
      </g>

      
      <circle cx="250" cy="75" r="6" class="point-key" />
      <g class="label-key" transform="translate(258, 66)">
        <rect x="0" y="0" width="38" height="18" class="label-pill" />
        <text x="19" y="12" text-anchor="middle" font-size="10" fill="#1e2945">(2, 3)</text>
      </g>

      
      <g class="caption-banner" transform="translate(180, 342)">
        <rect x="-115" y="-14" width="230" height="24" rx="12" fill="#eff6ff" stroke="#93c5fd" stroke-width="1" filter="url(#shadow)" />
        <text x="0" y="2" class="caption-text">y = 2x − 1 (All infinite solutions)</text>
      </g>
    </svg>
  </div>

  <script>
    let currentStep = 1;
    let isPlaying = true;
    let timer = null;

    function setStep(step) {
      currentStep = step;
      document.body.setAttribute('data-step', step);
      document.querySelectorAll('.step-btn').forEach((btn, idx) => {
        btn.classList.toggle('active', idx + 1 === step);
      });
    }

    function nextStep() {
      const next = (currentStep % 3) + 1;
      setStep(next);
    }

    function startAutoPlay() {
      stopAutoPlay();
      timer = setInterval(nextStep, 3200);
      document.getElementById('playToggle').textContent = '⏸';
      isPlaying = true;
    }

    function stopAutoPlay() {
      if (timer) {
        clearInterval(timer);
        timer = null;
      }
      document.getElementById('playToggle').textContent = '▶';
      isPlaying = false;
    }

    function togglePlay() {
      if (isPlaying) {
        stopAutoPlay();
      } else {
        nextStep();
        startAutoPlay();
      }
    }

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

HSA.REI.D.10

Aligned learning resources

Related diagrams