<!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>CPCTC: Corresponding Parts</title>
  <style>
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      max-width: 540px;
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      font-size: 11px;
      font-weight: 700;
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      letter-spacing: 0.04em;
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      font-size: 13px;
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      height: 9px;
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</head>
<body>

  
  <header class="header">
    <div class="title">Corresponding Parts of Congruent Triangles (CPCTC)</div>
    <div class="badge-bar">
      <span class="badge-main">△ABC ≅ △DEF</span>
      <span class="map-badge">(A↔D, B↔E, C↔F)</span>
    </div>
  </header>

  
  <div class="svg-container">
    <svg viewBox="0 0 460 210" aria-label="Congruent Triangles ABC and DEF">
      <defs>
        
      </defs>

      
      <g opacity="0.35" stroke="#94a3b8" stroke-dasharray="3 3" stroke-width="1.2">
        <line x1="75" y1="35" x2="305" y2="35" />
        <line x1="30" y1="175" x2="260" y2="175" />
        <line x1="185" y1="165" x2="415" y2="165" />
      </g>

      
      
      <polygon points="75,35 30,175 185,165" class="tri-fill tri-outline" />

      
      
      <g class="geom-part c-cyan" data-key="angA" stroke="#0284c7" stroke-width="2.2" fill="none">
        <path d="M 68,56 A 25 25 0 0 0 88,50" />
      </g>
      
      <g class="geom-part c-purple" data-key="angB" stroke="#9333ea" stroke-width="2.2" fill="none">
        <path d="M 39,147 A 30 30 0 0 1 59,173" />
        <path d="M 46,143 A 36 36 0 0 1 66,172" />
      </g>
      
      <g class="geom-part c-pink" data-key="angC" stroke="#db2777" stroke-width="2.2" fill="none">
        <path d="M 158,166 A 28 28 0 0 1 170,147" />
        <path d="M 152,166 A 34 34 0 0 1 166,143" />
        <path d="M 146,167 A 40 40 0 0 1 162,139" />
      </g>

      
      
      <g class="geom-part c-blue" data-key="side1">
        <line x1="75" y1="35" x2="30" y2="175" stroke="#2563eb" stroke-width="3" stroke-linecap="round" />
        <line x1="46" y1="102" x2="58" y2="107" stroke="#2563eb" stroke-width="2.5" stroke-linecap="round" />
      </g>
      
      <g class="geom-part c-green" data-key="side2">
        <line x1="30" y1="175" x2="185" y2="165" stroke="#16a34a" stroke-width="3" stroke-linecap="round" />
        <line x1="104" y1="165" x2="102" y2="177" stroke="#16a34a" stroke-width="2.5" stroke-linecap="round" />
        <line x1="110" y1="165" x2="108" y2="177" stroke="#16a34a" stroke-width="2.5" stroke-linecap="round" />
      </g>
      
      <g class="geom-part c-orange" data-key="side3">
        <line x1="75" y1="35" x2="185" y2="165" stroke="#ea580c" stroke-width="3" stroke-linecap="round" />
        <line x1="123" y1="104" x2="135" y2="94" stroke="#ea580c" stroke-width="2.5" stroke-linecap="round" />
        <line x1="128" y1="109" x2="140" y2="99" stroke="#ea580c" stroke-width="2.5" stroke-linecap="round" />
        <line x1="133" y1="114" x2="145" y2="104" stroke="#ea580c" stroke-width="2.5" stroke-linecap="round" />
      </g>

      
      <text x="75" y="18" class="v-label">A</text>
      <text x="14" y="184" class="v-label">B</text>
      <text x="201" y="174" class="v-label">C</text>


      
      
      <polygon points="305,35 260,175 415,165" class="tri-fill tri-outline" />

      
      
      <g class="geom-part c-cyan" data-key="angA" stroke="#0284c7" stroke-width="2.2" fill="none">
        <path d="M 298,56 A 25 25 0 0 0 318,50" />
      </g>
      
      <g class="geom-part c-purple" data-key="angB" stroke="#9333ea" stroke-width="2.2" fill="none">
        <path d="M 269,147 A 30 30 0 0 1 289,173" />
        <path d="M 276,143 A 36 36 0 0 1 296,172" />
      </g>
      
      <g class="geom-part c-pink" data-key="angC" stroke="#db2777" stroke-width="2.2" fill="none">
        <path d="M 388,166 A 28 28 0 0 1 400,147" />
        <path d="M 382,166 A 34 34 0 0 1 396,143" />
        <path d="M 376,167 A 40 40 0 0 1 392,139" />
      </g>

      
      
      <g class="geom-part c-blue" data-key="side1">
        <line x1="305" y1="35" x2="260" y2="175" stroke="#2563eb" stroke-width="3" stroke-linecap="round" />
        <line x1="276" y1="102" x2="288" y2="107" stroke="#2563eb" stroke-width="2.5" stroke-linecap="round" />
      </g>
      
      <g class="geom-part c-green" data-key="side2">
        <line x1="260" y1="175" x2="415" y2="165" stroke="#16a34a" stroke-width="3" stroke-linecap="round" />
        <line x1="334" y1="165" x2="332" y2="177" stroke="#16a34a" stroke-width="2.5" stroke-linecap="round" />
        <line x1="340" y1="165" x2="338" y2="177" stroke="#16a34a" stroke-width="2.5" stroke-linecap="round" />
      </g>
      
      <g class="geom-part c-orange" data-key="side3">
        <line x1="305" y1="35" x2="415" y2="165" stroke="#ea580c" stroke-width="3" stroke-linecap="round" />
        <line x1="353" y1="104" x2="365" y2="94" stroke="#ea580c" stroke-width="2.5" stroke-linecap="round" />
        <line x1="358" y1="109" x2="370" y2="99" stroke="#ea580c" stroke-width="2.5" stroke-linecap="round" />
        <line x1="363" y1="114" x2="375" y2="104" stroke="#ea580c" stroke-width="2.5" stroke-linecap="round" />
      </g>

      
      <text x="305" y="18" class="v-label">D</text>
      <text x="244" y="184" class="v-label">E</text>
      <text x="431" y="174" class="v-label">F</text>
    </svg>
  </div>

  
  <div class="matrix-section">
    <div class="columns-wrap">
      
      <div class="matrix-col">
        <div class="col-header">Congruent Sides</div>
        <button class="pill-btn c-blue" data-target="side1">
          <div class="pill-content">
            <span class="pill-tag bg-blue"></span>
            <span>AB ≅ DE</span>
          </div>
          <span>1 tick</span>
        </button>
        <button class="pill-btn c-green" data-target="side2">
          <div class="pill-content">
            <span class="pill-tag bg-green"></span>
            <span>BC ≅ EF</span>
          </div>
          <span>2 ticks</span>
        </button>
        <button class="pill-btn c-orange" data-target="side3">
          <div class="pill-content">
            <span class="pill-tag bg-orange"></span>
            <span>AC ≅ DF</span>
          </div>
          <span>3 ticks</span>
        </button>
      </div>

      
      <div class="matrix-col">
        <div class="col-header">Congruent Angles</div>
        <button class="pill-btn c-cyan" data-target="angA">
          <div class="pill-content">
            <span class="pill-tag bg-cyan"></span>
            <span>∠A ≅ ∠D</span>
          </div>
          <span>1 arc</span>
        </button>
        <button class="pill-btn c-purple" data-target="angB">
          <div class="pill-content">
            <span class="pill-tag bg-purple"></span>
            <span>∠B ≅ ∠E</span>
          </div>
          <span>2 arcs</span>
        </button>
        <button class="pill-btn c-pink" data-target="angC">
          <div class="pill-content">
            <span class="pill-tag bg-pink"></span>
            <span>∠C ≅ ∠F</span>
          </div>
          <span>3 arcs</span>
        </button>
      </div>
    </div>

    
    <button class="reset-btn" id="resetBtn">Show All Correspondences</button>
  </div>

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      // Update Pill buttons state
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</body>
</html>

Understanding Geometric Congruence and CPCTC

<!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>CPCTC Worked Example</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }

    body {
      background: #ffffff;
      color: #1e293b;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
    }

    .app-container {
      width: 100%;
      max-width: 540px;
      display: flex;
      flex-direction: column;
      gap: 10px;
    }

    /* Congruence statement bar */
    .statement-box {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 8px 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 4px;
    }

    .statement-row {
      display: flex;
      align-items: center;
      gap: 12px;
      font-size: 20px;
      font-weight: 700;
      letter-spacing: 0.5px;
    }

    .tri-letters {
      display: inline-flex;
      gap: 2px;
    }

    .letter {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      width: 24px;
      height: 28px;
      border-radius: 6px;
      transition: background-color 0.25s, color 0.25s, box-shadow 0.25s;
    }

    .pos-tags {
      display: flex;
      justify-content: space-between;
      width: 76px;
      font-size: 10px;
      font-weight: 600;
      color: #94a3b8;
      padding: 0 4px;
    }

    /* Color highlights for correspondence */
    .hl-blue {
      background: #dbeafe;
      color: #1d4ed8;
      box-shadow: inset 0 0 0 1.5px #3b82f6;
    }

    .hl-green {
      background: #d1fae5;
      color: #047857;
      box-shadow: inset 0 0 0 1.5px #10b981;
    }

    /* Visual Triangles Area */
    .triangles-view {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
      width: 100%;
    }

    .tri-card {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
    }

    .tri-svg {
      width: 100%;
      height: 110px;
      overflow: visible;
    }

    /* Side label styling in SVG */
    .side-label {
      font-size: 12px;
      font-weight: 700;
      fill: #475569;
    }

    .side-label.blue-active {
      fill: #1d4ed8;
      font-weight: 800;
    }

    .side-label.green-active {
      fill: #047857;
      font-weight: 800;
    }

    .tri-edge {
      stroke: #cbd5e1;
      stroke-width: 2.5;
      stroke-linecap: round;
      transition: stroke 0.25s, stroke-width 0.25s;
    }

    .tri-edge.blue-active {
      stroke: #2563eb;
      stroke-width: 4;
    }

    .tri-edge.green-active {
      stroke: #059669;
      stroke-width: 4;
    }

    /* Math Step Box */
    .step-display {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 12px;
      padding: 10px 14px;
      min-height: 94px;
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
      text-align: center;
      gap: 6px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }

    .step-badge {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      padding: 2px 8px;
      border-radius: 999px;
      background: #eff6ff;
      color: #1d4ed8;
    }

    .math-main {
      font-size: 18px;
      font-weight: 700;
      color: #0f172a;
      display: flex;
      align-items: center;
      gap: 8px;
      flex-wrap: wrap;
      justify-content: center;
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    .math-sub {
      font-size: 13px;
      font-weight: 600;
      color: #64748b;
    }

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    .controls {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
      width: 100%;
      padding-top: 2px;
    }

    .step-pills {
      display: flex;
      gap: 6px;
      align-items: center;
    }

    .pill-btn {
      border: 1px solid #cbd5e1;
      background: #f8fafc;
      color: #475569;
      font-size: 12px;
      font-weight: 700;
      padding: 6px 12px;
      border-radius: 8px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 4px;
      transition: background 0.15s, color 0.15s, border-color 0.15s;
    }

    .pill-btn.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
    }

    .nav-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      color: #1e293b;
      font-size: 13px;
      font-weight: 600;
      padding: 6px 12px;
      border-radius: 8px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      transition: background 0.15s;
    }

    .nav-btn:hover {
      background: #e2e8f0;
    }

    @media (max-width: 400px) {
      .pill-btn {
        padding: 6px 8px;
        font-size: 11px;
      }
      .statement-row {
        font-size: 17px;
      }
      .math-main {
        font-size: 16px;
      }
    }
  </style>
</head>
<body>

<div class="app-container">
  
  <div class="statement-box">
    <div class="statement-row">
      <div style="display:flex; flex-direction:column; align-items:center;">
        <div class="tri-letters">
          <span>△</span>
          <span id="let-p" class="letter">P</span>
          <span id="let-q" class="letter">Q</span>
          <span id="let-r" class="letter">R</span>
        </div>
        <div class="pos-tags">
          <span>1st</span><span>2nd</span><span>3rd</span>
        </div>
      </div>

      <span style="color:#64748b; font-weight:800; font-size:18px;">≅</span>

      <div style="display:flex; flex-direction:column; align-items:center;">
        <div class="tri-letters">
          <span>△</span>
          <span id="let-s" class="letter">S</span>
          <span id="let-t" class="letter">T</span>
          <span id="let-u" class="letter">U</span>
        </div>
        <div class="pos-tags">
          <span>1st</span><span>2nd</span><span>3rd</span>
        </div>
      </div>
    </div>
  </div>

  
  <div class="triangles-view">
    
    <div class="tri-card">
      <svg class="tri-svg" viewBox="0 0 160 110">
        
        <line id="edge-pr" class="tri-edge" x1="25" y1="90" x2="135" y2="90" />
        <line id="edge-qr" class="tri-edge" x1="25" y1="20" x2="135" y2="90" />
        <line id="edge-pq" class="tri-edge" x1="25" y1="90" x2="25" y2="20" />

        
        <circle cx="25" cy="90" r="3.5" fill="#1e293b" />
        <circle cx="25" cy="20" r="3.5" fill="#1e293b" />
        <circle cx="135" cy="90" r="3.5" fill="#1e293b" />

        <text x="12" y="96" font-size="12" font-weight="700" fill="#1e293b">P</text>
        <text x="12" y="20" font-size="12" font-weight="700" fill="#1e293b">Q</text>
        <text x="142" y="96" font-size="12" font-weight="700" fill="#1e293b">R</text>

        
        <text id="lbl-pq" class="side-label" x="32" y="58" text-anchor="start">2x + 5</text>
        <text id="lbl-pr" class="side-label" x="80" y="105" text-anchor="middle">PR = ?</text>
      </svg>
    </div>

    
    <div class="tri-card">
      <svg class="tri-svg" viewBox="0 0 160 110">
        
        <line id="edge-su" class="tri-edge" x1="25" y1="90" x2="135" y2="90" />
        <line id="edge-tu" class="tri-edge" x1="25" y1="20" x2="135" y2="90" />
        <line id="edge-st" class="tri-edge" x1="25" y1="90" x2="25" y2="20" />

        
        <circle cx="25" cy="90" r="3.5" fill="#1e293b" />
        <circle cx="25" cy="20" r="3.5" fill="#1e293b" />
        <circle cx="135" cy="90" r="3.5" fill="#1e293b" />

        <text x="12" y="96" font-size="12" font-weight="700" fill="#1e293b">S</text>
        <text x="12" y="20" font-size="12" font-weight="700" fill="#1e293b">T</text>
        <text x="142" y="96" font-size="12" font-weight="700" fill="#1e293b">U</text>

        
        <text id="lbl-st" class="side-label" x="32" y="58" text-anchor="start">19</text>
        <text id="lbl-su" class="side-label" x="80" y="105" text-anchor="middle">14</text>
      </svg>
    </div>
  </div>

  
  <div class="step-display">
    <div id="step-badge" class="step-badge">Step 1 of 4</div>
    <div id="step-math" class="math-main">PQ corresponds to ST</div>
    <div id="step-desc" class="math-sub">Letters 1–2 match letters 1–2</div>
  </div>

  
  <div class="controls">
    <button class="nav-btn" onclick="prevStep()">◀</button>
    <div class="step-pills">
      <button class="pill-btn active" onclick="goToStep(0)">1: Match</button>
      <button class="pill-btn" onclick="goToStep(1)">2: Setup</button>
      <button class="pill-btn" onclick="goToStep(2)">3: Solve</button>
      <button class="pill-btn" onclick="goToStep(3)">4: PR</button>
    </div>
    <button id="play-btn" class="nav-btn" onclick="togglePlay()">⏸</button>
    <button class="nav-btn" onclick="nextStep()">▶</button>
  </div>
</div>

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

  const stepsData = [
    {
      badge: "Step 1: Corresponding Sides",
      math: '<span style="color:#2563eb;">PQ</span> = <span style="color:#2563eb;">ST</span> &nbsp;|&nbsp; <span style="color:#059669;">PR</span> = <span style="color:#059669;">SU</span>',
      sub: "1st-2nd letters & 1st-3rd letters correspond",
      hlBlue: ['let-p', 'let-q', 'let-s', 'let-t'],
      hlGreen: ['let-r', 'let-u'],
      edgeBlue: ['edge-pq', 'edge-st'],
      edgeGreen: ['edge-pr', 'edge-su'],
      lblBlue: ['lbl-pq', 'lbl-st'],
      lblGreen: ['lbl-su'],
      prText: "PR = ?"
    },
    {
      badge: "Step 2: Set Up Equation",
      math: '2x + 5 = 19',
      sub: "Substitute side lengths: PQ = ST",
      hlBlue: ['let-p', 'let-q', 'let-s', 'let-t'],
      hlGreen: [],
      edgeBlue: ['edge-pq', 'edge-st'],
      edgeGreen: [],
      lblBlue: ['lbl-pq', 'lbl-st'],
      lblGreen: [],
      prText: "PR = ?"
    },
    {
      badge: "Step 3: Solve for x",
      math: '2x = 14 &nbsp;➔&nbsp; <span style="color:#2563eb;">x = 7</span>',
      sub: "Subtract 5, then divide by 2",
      hlBlue: ['let-p', 'let-q', 'let-s', 'let-t'],
      hlGreen: [],
      edgeBlue: ['edge-pq', 'edge-st'],
      edgeGreen: [],
      lblBlue: ['lbl-pq', 'lbl-st'],
      lblGreen: [],
      prText: "PR = ?"
    },
    {
      badge: "Step 4: Find PR using CPCTC",
      math: 'PR = SU &nbsp;➔&nbsp; <span style="color:#059669;">PR = 14</span>',
      sub: "Corresponding side length is exact duplicate",
      hlBlue: [],
      hlGreen: ['let-p', 'let-r', 'let-s', 'let-u'],
      edgeBlue: [],
      edgeGreen: ['edge-pr', 'edge-su'],
      lblBlue: [],
      lblGreen: ['lbl-pr', 'lbl-su'],
      prText: "PR = 14"
    }
  ];

  function renderStep(idx) {
    const data = stepsData[idx];

    // Update text
    document.getElementById('step-badge').textContent = data.badge;
    document.getElementById('step-math').innerHTML = data.math;
    document.getElementById('step-desc').textContent = data.sub;
    document.getElementById('lbl-pr').textContent = data.prText;

    // Reset all highlights
    const allLetters = ['let-p', 'let-q', 'let-r', 'let-s', 'let-t', 'let-u'];
    allLetters.forEach(id => {
      const el = document.getElementById(id);
      el.className = 'letter';
    });

    const allEdges = ['edge-pq', 'edge-pr', 'edge-qr', 'edge-st', 'edge-su', 'edge-tu'];
    allEdges.forEach(id => {
      const el = document.getElementById(id);
      el.classList.remove('blue-active', 'green-active');
    });

    const allLabels = ['lbl-pq', 'lbl-pr', 'lbl-st', 'lbl-su'];
    allLabels.forEach(id => {
      const el = document.getElementById(id);
      el.classList.remove('blue-active', 'green-active');
    });

    // Apply Blue Highlights
    data.hlBlue.forEach(id => document.getElementById(id).classList.add('hl-blue'));
    data.edgeBlue.forEach(id => document.getElementById(id).classList.add('blue-active'));
    data.lblBlue.forEach(id => document.getElementById(id).classList.add('blue-active'));

    // Apply Green Highlights
    data.hlGreen.forEach(id => document.getElementById(id).classList.add('hl-green'));
    data.edgeGreen.forEach(id => document.getElementById(id).classList.add('green-active'));
    data.lblGreen.forEach(id => document.getElementById(id).classList.add('green-active'));

    // Update buttons
    const pills = document.querySelectorAll('.pill-btn');
    pills.forEach((p, i) => {
      if (i === idx) p.classList.add('active');
      else p.classList.remove('active');
    });
  }

  function goToStep(idx) {
    currentStep = idx;
    renderStep(currentStep);
    resetTimer();
  }

  function nextStep() {
    currentStep = (currentStep + 1) % stepsData.length;
    renderStep(currentStep);
    resetTimer();
  }

  function prevStep() {
    currentStep = (currentStep - 1 + stepsData.length) % stepsData.length;
    renderStep(currentStep);
    resetTimer();
  }

  function togglePlay() {
    isPlaying = !isPlaying;
    document.getElementById('play-btn').textContent = isPlaying ? '⏸' : '▶';
    if (isPlaying) {
      startTimer();
    } else {
      clearInterval(timer);
    }
  }

  function startTimer() {
    clearInterval(timer);
    timer = setInterval(() => {
      currentStep = (currentStep + 1) % stepsData.length;
      renderStep(currentStep);
    }, 4000);
  }

  function resetTimer() {
    if (isPlaying) {
      startTimer();
    }
  }

  // Initial render
  renderStep(0);
  startTimer();
</script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      width: 100%;
      background: #f8f9fa;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 10px 8px;
      user-select: none;
    }

    .header-info {
      text-align: center;
      margin-bottom: 6px;
    }

    .step-desc {
      font-size: 13px;
      font-weight: 600;
      color: #4f46e5;
      min-height: 18px;
      transition: color 0.2s ease;
    }

    .controls {
      display: flex;
      flex-wrap: wrap;
      gap: 5px;
      justify-content: center;
      align-items: center;
      width: 100%;
      max-width: 520px;
      margin-bottom: 8px;
    }

    .btn {
      appearance: none;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #1e2945;
      padding: 5px 10px;
      border-radius: 18px;
      font-size: 12px;
      font-weight: 600;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 4px;
      transition: background-color 0.15s, color 0.15s, border-color 0.15s, box-shadow 0.15s;
    }

    .btn:hover {
      border-color: #94a3b8;
      background: #f1f5f9;
    }

    .btn.active {
      background: #4f46e5;
      border-color: #4f46e5;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(79, 70, 229, 0.3);
    }

    .btn-play {
      width: 28px;
      height: 28px;
      padding: 0;
      border-radius: 50%;
      font-size: 11px;
    }

    @media (max-width: 400px) {
      .btn {
        padding: 4px 7px;
        font-size: 11px;
      }
      .btn-play {
        width: 26px;
        height: 26px;
      }
      .step-desc {
        font-size: 12px;
      }
    }

    .diagram-area {
      width: 100%;
      max-width: 520px;
      position: relative;
    }

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

    .congruence-badge {
      position: absolute;
      bottom: 6px;
      left: 50%;
      transform: translateX(-50%) translateY(6px);
      background: #4f46e5;
      color: #ffffff;
      font-size: 14px;
      font-weight: 700;
      padding: 5px 16px;
      border-radius: 20px;
      box-shadow: 0 3px 10px rgba(79, 70, 229, 0.35);
      opacity: 0;
      pointer-events: none;
      transition: opacity 0.3s ease, transform 0.3s ease;
      letter-spacing: 0.5px;
      white-space: nowrap;
    }

    .congruence-badge.visible {
      opacity: 1;
      transform: translateX(-50%) translateY(0);
    }

    .v-label {
      font-size: 14px;
      font-weight: 700;
      fill: #1e2945;
      text-anchor: middle;
      dominant-baseline: central;
    }

    .s-label {
      font-size: 12px;
      font-weight: 600;
      fill: #64748b;
      text-anchor: middle;
      dominant-baseline: central;
    }

    .lbl-blue {
      fill: #4f46e5;
      font-weight: 700;
    }

    .ghost-line {
      stroke: #cbd5e1;
      stroke-dasharray: 4,4;
      stroke-width: 1.5;
    }
  </style>
</head>
<body>

  <div class="header-info">
    <div class="step-desc" id="stepDesc">Initial position of △ABC and target △DEF</div>
  </div>

  <div class="controls">
    <button class="btn btn-play" id="playBtn" title="Play / Pause">⏸</button>
    <button class="btn active" data-step="0">Start</button>
    <button class="btn" data-step="1">1. Translate</button>
    <button class="btn" data-step="2">2. Rotate</button>
    <button class="btn" data-step="3">3. Reflect</button>
  </div>

  <div class="diagram-area">
    <svg viewBox="0 0 520 235">
      <defs>
        
        <filter id="glow" x="-30%" y="-30%" width="160%" height="160%">
          <feGaussianBlur stdDeviation="3" result="blur" />
          <feComposite in="SourceGraphic" in2="blur" operator="over" />
        </filter>
      </defs>

      
      <g id="targetGroup">
        <polygon points="440,70 440,190 350,190" fill="#f1f5f9" stroke="#94a3b8" stroke-width="2" stroke-dasharray="5,4" stroke-linejoin="round"/>
        
        <path d="M 426 190 L 426 176 L 440 176" fill="none" stroke="#94a3b8" stroke-width="1.5" />
        
        <text class="s-label" x="456" y="130">4</text>
        <text class="s-label" x="395" y="206">3</text>
        <text class="s-label" x="382" y="120">5</text>
        
        <text class="v-label" x="440" y="52">D</text>
        <text class="v-label" x="456" y="196">E</text>
        <text class="v-label" x="334" y="196">F</text>
      </g>

      
      <line id="reflAxis" x1="395" y1="35" x2="395" y2="215" stroke="#a5b4fc" stroke-width="1.5" stroke-dasharray="4,4" opacity="0"/>
      <text id="reflLabel" x="395" y="26" font-size="11" font-weight="600" fill="#6366f1" text-anchor: middle text-anchor="middle" opacity="0">Line of Reflection</text>

      
      <g id="movingGroup">
        
        <polygon id="glowPoly" points="160,190 160,100 40,190" fill="none" stroke="#4f46e5" stroke-width="6" stroke-linejoin="round" opacity="0" filter="url(#glow)"/>
        
        <polygon id="polyABC" points="160,190 160,100 40,190" fill="rgba(79, 70, 229, 0.18)" stroke="#4f46e5" stroke-width="2.5" stroke-linejoin="round"/>
        
        <path id="rightAngleMark" d="M 160 176 L 146 176 L 146 190" fill="none" stroke="#4f46e5" stroke-width="1.5" />

        
        <circle id="dotA" cx="160" cy="190" r="4.5" fill="#4f46e5" stroke="#ffffff" stroke-width="1.5"/>
        <circle id="dotB" cx="160" cy="100" r="4.5" fill="#4f46e5" stroke="#ffffff" stroke-width="1.5"/>
        <circle id="dotC" cx="40" cy="190" r="4.5" fill="#4f46e5" stroke="#ffffff" stroke-width="1.5"/>

        
        <text id="lblAB" class="s-label lbl-blue" x="176" y="145">3</text>
        <text id="lblAC" class="s-label lbl-blue" x="100" y="206">4</text>
        <text id="lblBC" class="s-label lbl-blue" x="90" y="135">5</text>

        
        <text id="txtA" class="v-label" x="176" y="200">A</text>
        <text id="txtB" class="v-label" x="160" y="82">B</text>
        <text id="txtC" class="v-label" x="25" y="195">C</text>
      </g>
    </svg>

    <div class="congruence-badge" id="badge">△ABC ≅ △DEF</div>
  </div>

  <script>
    // Exact geometric states mapping ABC onto DEF
    // Leg AB = 3 (90px), Leg AC = 4 (120px), Hypotenuse BC = 5 (150px)
    const states = [
      // 0: Start
      {
        desc: "Initial position of △ABC and target △DEF",
        A: { x: 160, y: 190 },
        B: { x: 160, y: 100 },
        C: { x: 40, y: 190 },
        lblAB: { x: 176, y: 145 },
        lblAC: { x: 100, y: 206 },
        lblBC: { x: 90, y: 135 },
        txtA: { x: 176, y: 200 },
        txtB: { x: 160, y: 82 },
        txtC: { x: 25, y: 195 },
        refl: 0
      },
      // 1: Translate (slide right +90px)
      {
        desc: "1. Translation: slide △ABC horizontally by +90 px",
        A: { x: 250, y: 190 },
        B: { x: 250, y: 100 },
        C: { x: 130, y: 190 },
        lblAB: { x: 266, y: 145 },
        lblAC: { x: 190, y: 206 },
        lblBC: { x: 180, y: 135 },
        txtA: { x: 266, y: 200 },
        txtB: { x: 250, y: 82 },
        txtC: { x: 115, y: 195 },
        refl: 0
      },
      // 2: Rotate 90° clockwise around A(250, 190)
      {
        desc: "2. Rotation: turn △ABC 90° clockwise about vertex A",
        A: { x: 250, y: 190 },
        B: { x: 340, y: 190 },
        C: { x: 250, y: 70 },
        lblAB: { x: 295, y: 206 },
        lblAC: { x: 234, y: 130 },
        lblBC: { x: 305, y: 120 },
        txtA: { x: 235, y: 200 },
        txtB: { x: 355, y: 195 },
        txtC: { x: 250, y: 52 },
        refl: 0.8
      },
      // 3: Reflect across line x = 395 onto DEF
      {
        desc: "3. Reflection: flip △ABC across the line to overlap △DEF",
        A: { x: 440, y: 190 }, // maps to E
        B: { x: 350, y: 190 }, // maps to F
        C: { x: 440, y: 70 },  // maps to D
        lblAB: { x: 395, y: 206 },
        lblAC: { x: 456, y: 130 },
        lblBC: { x: 382, y: 120 },
        txtA: { x: 456, y: 196 },
        txtB: { x: 334, y: 196 },
        txtC: { x: 440, y: 52 },
        refl: 0
      }
    ];

    let current = 0;
    let playing = true;
    let autoTimer = null;
    let animFrame = null;

    // Current animated coordinates
    const cur = JSON.parse(JSON.stringify(states[0]));
    let curRefl = 0;
    let glowOpacity = 0;

    const polyABC = document.getElementById('polyABC');
    const glowPoly = document.getElementById('glowPoly');
    const rightAngleMark = document.getElementById('rightAngleMark');
    const dotA = document.getElementById('dotA');
    const dotB = document.getElementById('dotB');
    const dotC = document.getElementById('dotC');
    const txtA = document.getElementById('txtA');
    const txtB = document.getElementById('txtB');
    const txtC = document.getElementById('txtC');
    const lblAB = document.getElementById('lblAB');
    const lblAC = document.getElementById('lblAC');
    const lblBC = document.getElementById('lblBC');
    const reflAxis = document.getElementById('reflAxis');
    const reflLabel = document.getElementById('reflLabel');
    const badge = document.getElementById('badge');
    const stepDesc = document.getElementById('stepDesc');
    const playBtn = document.getElementById('playBtn');
    const stepBtns = document.querySelectorAll('[data-step]');

    function updateRightAngleMark(A, B, C) {
      const v1x = B.x - A.x, v1y = B.y - A.y;
      const len1 = Math.hypot(v1x, v1y) || 1;
      const u1x = (v1x / len1) * 14, u1y = (v1y / len1) * 14;

      const v2x = C.x - A.x, v2y = C.y - A.y;
      const len2 = Math.hypot(v2x, v2y) || 1;
      const u2x = (v2x / len2) * 14, u2y = (v2y / len2) * 14;

      const p1x = A.x + u1x, p1y = A.y + u1y;
      const p2x = A.x + u1x + u2x, p2y = A.y + u1y + u2y;
      const p3x = A.x + u2x, p3y = A.y + u2y;

      rightAngleMark.setAttribute('d', `M ${p1x} ${p1y} L ${p2x} ${p2y} L ${p3x} ${p3y}`);
    }

    function render() {
      const pts = `${cur.A.x},${cur.A.y} ${cur.B.x},${cur.B.y} ${cur.C.x},${cur.C.y}`;
      polyABC.setAttribute('points', pts);
      glowPoly.setAttribute('points', pts);
      glowPoly.setAttribute('opacity', glowOpacity);

      updateRightAngleMark(cur.A, cur.B, cur.C);

      dotA.setAttribute('cx', cur.A.x);
      dotA.setAttribute('cy', cur.A.y);
      dotB.setAttribute('cx', cur.B.x);
      dotB.setAttribute('cy', cur.B.y);
      dotC.setAttribute('cx', cur.C.x);
      dotC.setAttribute('cy', cur.C.y);

      txtA.setAttribute('x', cur.txtA.x);
      txtA.setAttribute('y', cur.txtA.y);
      txtB.setAttribute('x', cur.txtB.x);
      txtB.setAttribute('y', cur.txtB.y);
      txtC.setAttribute('x', cur.txtC.x);
      txtC.setAttribute('y', cur.txtC.y);

      lblAB.setAttribute('x', cur.lblAB.x);
      lblAB.setAttribute('y', cur.lblAB.y);
      lblAC.setAttribute('x', cur.lblAC.x);
      lblAC.setAttribute('y', cur.lblAC.y);
      lblBC.setAttribute('x', cur.lblBC.x);
      lblBC.setAttribute('y', cur.lblBC.y);

      reflAxis.setAttribute('opacity', curRefl);
      reflLabel.setAttribute('opacity', curRefl);
    }

    function easeInOutCubic(t) {
      return t < 0.5 ? 4 * t * t * t : 1 - Math.pow(-2 * t + 2, 3) / 2;
    }

    function animateTo(targetIndex, duration = 750) {
      if (animFrame) cancelAnimationFrame(animFrame);

      current = targetIndex;
      stepBtns.forEach((b, i) => b.classList.toggle('active', i === current));
      stepDesc.textContent = states[current].desc;

      const target = states[current];
      const startState = JSON.parse(JSON.stringify(cur));
      const startRefl = curRefl;
      const targetRefl = target.refl;

      const startTime = performance.now();

      function update(now) {
        const elapsed = now - startTime;
        const progress = Math.min(1, elapsed / duration);
        const ease = easeInOutCubic(progress);

        // Interpolate points
        ['A', 'B', 'C', 'txtA', 'txtB', 'txtC', 'lblAB', 'lblAC', 'lblBC'].forEach(k => {
          cur[k].x = startState[k].x + (target[k].x - startState[k].x) * ease;
          cur[k].y = startState[k].y + (target[k].y - startState[k].y) * ease;
        });

        curRefl = startRefl + (targetRefl - startRefl) * ease;

        if (current === 3 && progress > 0.8) {
          glowOpacity = Math.sin((progress - 0.8) / 0.2 * Math.PI) * 0.85;
        } else {
          glowOpacity = Math.max(0, glowOpacity - 0.05);
        }

        render();

        if (progress < 1) {
          animFrame = requestAnimationFrame(update);
        } else {
          // Finalize state values exactly
          ['A', 'B', 'C', 'txtA', 'txtB', 'txtC', 'lblAB', 'lblAC', 'lblBC'].forEach(k => {
            cur[k].x = target[k].x;
            cur[k].y = target[k].y;
          });
          curRefl = targetRefl;

          if (current === 3) {
            badge.classList.add('visible');
            triggerGlowPulse();
          } else {
            badge.classList.remove('visible');
            glowOpacity = 0;
            render();
          }
        }
      }

      if (current !== 3) {
        badge.classList.remove('visible');
      }

      animFrame = requestAnimationFrame(update);
    }

    function triggerGlowPulse() {
      let startTime = performance.now();
      function pulse(now) {
        let t = (now - startTime) / 600;
        if (t <= 1) {
          glowOpacity = Math.sin(t * Math.PI) * 0.9;
          render();
          requestAnimationFrame(pulse);
        } else {
          glowOpacity = 0;
          render();
        }
      }
      requestAnimationFrame(pulse);
    }

    function nextStep() {
      const next = (current + 1) % states.length;
      animateTo(next, next === 0 ? 500 : 800);
    }

    function startAutoPlay() {
      playing = true;
      playBtn.textContent = '⏸';
      if (autoTimer) clearInterval(autoTimer);
      autoTimer = setInterval(nextStep, 2800);
    }

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

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

    stepBtns.forEach((btn, idx) => {
      btn.addEventListener('click', () => {
        stopAutoPlay();
        animateTo(idx);
      });
    });

    // Initial render and start
    render();
    startAutoPlay();
  </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;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      -webkit-tap-highlight-color: transparent;
    }

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

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

    /* Top: Geometry visualization */
    .geometry-box {
      width: 100%;
      display: flex;
      flex-direction: column;
      align-items: center;
    }

    svg {
      width: 100%;
      height: 130px;
      overflow: visible;
    }

    .slider-row {
      width: 100%;
      max-width: 320px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 10px;
      font-size: 13px;
      color: #64748b;
      font-weight: 500;
    }

    input[type=range] {
      flex: 1;
      height: 6px;
      border-radius: 3px;
      background: #e2e8f0;
      outline: none;
      accent-color: #2563eb;
      cursor: pointer;
    }

    /* Bottom: Conditional Cards */
    .flow-row {
      width: 100%;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
    }

    .cond-card {
      flex: 1;
      padding: 10px 8px;
      border-radius: 8px;
      text-align: center;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 4px;
    }

    .card-p {
      background: #f0fdf4;
      border: 1.5px solid #16a34a;
    }

    .card-q {
      background: #eff6ff;
      border: 1.5px solid #2563eb;
    }

    .card-tag {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      padding: 2px 6px;
      border-radius: 4px;
    }

    .card-p .card-tag {
      color: #15803d;
      background: #dcfce7;
    }

    .card-q .card-tag {
      color: #1d4ed8;
      background: #dbeafe;
    }

    .card-title {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      line-height: 1.2;
    }

    .card-desc {
      font-size: 12px;
      color: #475569;
      font-weight: 500;
    }

    .arrow-col {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      flex-shrink: 0;
      color: #64748b;
      gap: 2px;
    }

    .arrow-text {
      font-size: 11px;
      font-weight: 600;
      white-space: nowrap;
    }

    .arrow-icon {
      font-size: 18px;
      line-height: 1;
      color: #0f172a;
    }
  </style>
</head>
<body>

  <div class="diagram-area">
    
    <div class="geometry-box">
      <svg viewBox="0 0 360 130">
        <defs>
          <marker id="arrow" viewBox="0 0 10 10" refX="5" 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="#334155"/>
          </marker>
          <marker id="arrow-ray" viewBox="0 0 10 10" refX="5" 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="#0f172a"/>
          </marker>
        </defs>

        
        <line x1="30" y1="100" x2="330" y2="100" stroke="#334155" stroke-width="2.5" marker-start="url(#arrow)" marker-end="url(#arrow)"/>
        
        
        <circle cx="180" cy="100" r="3.5" fill="#0f172a"/>

        
        <path id="arc1" fill="rgba(22, 163, 74, 0.15)" stroke="#16a34a" stroke-width="2" />
        <path id="arc2" fill="rgba(37, 99, 235, 0.15)" stroke="#2563eb" stroke-width="2" />

        
        <line id="ray" x1="180" y1="100" x2="135" y2="25" stroke="#0f172a" stroke-width="2.5" marker-end="url(#arrow-ray)"/>

        
        <text id="label1" x="125" y="82" fill="#15803d" font-size="14" font-weight="700" text-anchor="middle">∠1 = 120°</text>
        <text id="label2" x="235" y="82" fill="#1d4ed8" font-size="14" font-weight="700" text-anchor="middle">∠2 = 60°</text>
      </svg>

      <div class="slider-row">
        <span>Adjust Ray:</span>
        <input type="range" id="angleSlider" min="35" max="145" value="60" aria-label="Adjust angle split">
      </div>
    </div>

    
    <div class="flow-row">
      
      <div class="cond-card card-p">
        <span class="card-tag">Hypothesis (p)</span>
        <div class="card-title">Linear Pair</div>
        <div class="card-desc">Two adjacent angles on a straight line</div>
      </div>

      
      <div class="arrow-col">
        <span class="arrow-text">leads to</span>
        <span class="arrow-icon">➔</span>
      </div>

      
      <div class="cond-card card-q">
        <span class="card-tag">Conclusion (q)</span>
        <div class="card-title">Supplementary</div>
        <div id="sum-desc" class="card-desc">∠1 + ∠2 = 180°</div>
      </div>
    </div>
  </div>

  <script>
    const slider = document.getElementById('angleSlider');
    const ray = document.getElementById('ray');
    const arc1 = document.getElementById('arc1');
    const arc2 = document.getElementById('arc2');
    const label1 = document.getElementById('label1');
    const label2 = document.getElementById('label2');

    const vx = 180;
    const vy = 100;
    const rayLen = 85;
    const r1 = 44;
    const r2 = 34;

    function updateAngles() {
      // deg2 is angle 2 in degrees (from right horizontal line to ray)
      const deg2 = parseInt(slider.value, 10);
      const deg1 = 180 - deg2;
      const rad2 = (deg2 * Math.PI) / 180;

      // Ray tip coordinates
      const rx = vx + rayLen * Math.cos(Math.PI - (deg1 * Math.PI / 180));
      const ry = vy - rayLen * Math.sin(Math.PI - (deg1 * Math.PI / 180));
      ray.setAttribute('x2', rx);
      ray.setAttribute('y2', ry);

      // Arc 2 (Right angle: 0 to deg2)
      const arc2EndX = vx + r2 * Math.cos(rad2);
      const arc2EndY = vy - r2 * Math.sin(rad2);
      const d2 = `M ${vx} ${vy} L ${vx + r2} ${vy} A ${r2} ${r2} 0 0 0 ${arc2EndX} ${arc2EndY} Z`;
      arc2.setAttribute('d', d2);

      // Arc 1 (Left angle: deg2 to 180)
      const arc1StartX = vx + r1 * Math.cos(rad2);
      const arc1StartY = vy - r1 * Math.sin(rad2);
      const d1 = `M ${vx} ${vy} L ${arc1StartX} ${arc1StartY} A ${r1} ${r1} 0 0 0 ${vx - r1} ${vy} Z`;
      arc1.setAttribute('d', d1);

      // Update Labels
      label1.textContent = `∠1 = ${deg1}°`;
      label2.textContent = `∠2 = ${deg2}°`;

      // Label positions along bisectors
      const bisect1 = Math.PI - ((deg1 / 2) * Math.PI / 180);
      const bisect2 = (deg2 / 2) * Math.PI / 180;
      
      label1.setAttribute('x', vx + 68 * Math.cos(bisect1));
      label1.setAttribute('y', vy - 54 * Math.sin(bisect1));

      label2.setAttribute('x', vx + 68 * Math.cos(bisect2));
      label2.setAttribute('y', vy - 54 * Math.sin(bisect2));
    }

    slider.addEventListener('input', updateAngles);
    updateAngles();
  </script>
</body>
</html>

Conditional Statements: Hypothesis and Conclusion

<!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: #1e293b;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 16px 12px;
      overflow-x: hidden;
    }

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

    .step-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      transition: all 0.25s ease;
    }

    .step-btn.active {
      background: #0ea5e9;
      border-color: #0284c7;
      color: #ffffff;
      box-shadow: 0 2px 4px rgba(14, 165, 233, 0.25);
    }

    .play-btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 50%;
      width: 32px;
      height: 32px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 13px;
      color: #334155;
      cursor: pointer;
      transition: background 0.2s;
    }

    .play-btn:active {
      background: #e2e8f0;
    }

    /* Stage Area */
    .stage {
      position: relative;
      width: 100%;
      max-width: 540px;
      flex: 1;
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
      gap: 16px;
      min-height: 280px;
    }

    /* Sentence Box 1 */
    .box {
      width: 100%;
      background: #f8fafc;
      border: 1.5px solid #e2e8f0;
      border-radius: 12px;
      padding: 14px 16px;
      text-align: center;
      font-size: 17px;
      font-weight: 500;
      color: #334155;
      line-height: 1.5;
      transition: all 0.3s ease;
    }

    /* Highlight Spans */
    .hl-green {
      display: inline-block;
      padding: 2px 6px;
      border-radius: 6px;
      transition: all 0.3s ease;
      color: inherit;
    }

    .hl-blue {
      display: inline-block;
      padding: 2px 6px;
      border-radius: 6px;
      transition: all 0.3s ease;
      color: inherit;
    }

    /* Step states for Highlights */
    .step-2 .hl-green,
    .step-3 .hl-green {
      background: #dcfce7;
      color: #15803d;
      font-weight: 700;
      box-shadow: inset 0 0 0 1px #86efac;
    }

    .step-2 .hl-blue,
    .step-3 .hl-blue {
      background: #dbeafe;
      color: #1d4ed8;
      font-weight: 700;
      box-shadow: inset 0 0 0 1px #93c5fd;
    }

    /* Arrow Connector */
    .arrow-container {
      display: flex;
      align-items: center;
      justify-content: center;
      color: #94a3b8;
      font-size: 20px;
      height: 24px;
      transition: all 0.3s ease;
      opacity: 0.2;
      transform: translateY(-2px);
    }

    .step-3 .arrow-container {
      opacity: 1;
      color: #0ea5e9;
      transform: translateY(0);
    }

    /* Step 3 Conditional Output */
    .conditional-box {
      width: 100%;
      background: #ffffff;
      border: 1.5px dashed #cbd5e1;
      border-radius: 12px;
      padding: 14px 16px;
      text-align: center;
      font-size: 17px;
      font-weight: 500;
      color: #94a3b8;
      transition: all 0.3s ease;
    }

    .step-3 .conditional-box {
      border: 1.5px solid #0ea5e9;
      background: #f0f9ff;
      color: #0f172a;
      box-shadow: 0 4px 12px rgba(14, 165, 233, 0.08);
    }

    .keyword {
      font-weight: 800;
      text-transform: uppercase;
      font-size: 15px;
      letter-spacing: 0.5px;
      color: #64748b;
    }

    .step-3 .keyword {
      color: #0284c7;
    }

    /* Chips row for p & q */
    .chips-row {
      display: flex;
      justify-content: center;
      gap: 12px;
      width: 100%;
      opacity: 0;
      transform: translateY(4px);
      transition: all 0.3s ease;
      pointer-events: none;
    }

    .step-3 .chips-row {
      opacity: 1;
      transform: translateY(0);
    }

    .chip {
      display: flex;
      align-items: center;
      gap: 6px;
      padding: 6px 12px;
      border-radius: 20px;
      font-size: 13px;
      font-weight: 600;
    }

    .chip-green {
      background: #dcfce7;
      color: #166534;
      border: 1px solid #86efac;
    }

    .chip-blue {
      background: #dbeafe;
      color: #1e40af;
      border: 1px solid #93c5fd;
    }

    .var {
      font-style: italic;
      font-family: "Times New Roman", Times, serif;
      font-size: 15px;
      font-weight: 700;
    }

    /* Instruction/Status Banner */
    .status-bar {
      font-size: 13px;
      font-weight: 600;
      color: #64748b;
      text-align: center;
      min-height: 18px;
    }
  </style>
</head>
<body>

  
  <div class="controls">
    <button class="step-btn active" onclick="setStep(1)">1. Original</button>
    <button class="step-btn" onclick="setStep(2)">2. Identify</button>
    <button class="step-btn" onclick="setStep(3)">3. Convert</button>
    <button class="play-btn" id="togglePlay" title="Auto play" onclick="togglePlay()">⏸</button>
  </div>

  
  <div class="stage" id="stage">
    
    
    <div class="box" id="origBox">
      All <span class="hl-green">right angles</span> <span class="hl-blue">measure 90°</span>.
    </div>

    
    <div class="arrow-container">
      ↓
    </div>

    
    <div class="conditional-box" id="condBox">
      <span class="keyword">If</span> an angle is a <span class="hl-green">right angle</span>,<br>
      <span class="keyword">then</span> its <span class="hl-blue">measure is 90°</span>.
    </div>

    
    <div class="chips-row">
      <div class="chip chip-green">
        <span class="var">p</span>: Hypothesis
      </div>
      <div class="chip chip-blue">
        <span class="var">q</span>: Conclusion
      </div>
    </div>

  </div>

  
  <div class="status-bar" id="statusBar">
    Standard statement
  </div>

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

    const descriptions = [
      "Standard statement",
      "Identify subject (p) and property (q)",
      "Form conditional: If p, then q"
    ];

    function updateView() {
      const stage = document.getElementById('stage');
      stage.className = 'stage step-' + currentStep;

      // Update buttons
      const buttons = document.querySelectorAll('.step-btn');
      buttons.forEach((btn, idx) => {
        if (idx + 1 === currentStep) {
          btn.classList.add('active');
        } else {
          btn.classList.remove('active');
        }
      });

      // Update description
      document.getElementById('statusBar').textContent = descriptions[currentStep - 1];
    }

    function setStep(step) {
      currentStep = step;
      updateView();
      if (isPlaying) {
        resetTimer();
      }
    }

    function nextStep() {
      currentStep = currentStep >= 3 ? 1 : currentStep + 1;
      updateView();
    }

    function resetTimer() {
      if (timer) clearInterval(timer);
      timer = setInterval(nextStep, 3500);
    }

    function togglePlay() {
      isPlaying = !isPlaying;
      const btn = document.getElementById('togglePlay');
      if (isPlaying) {
        btn.textContent = '⏸';
        resetTimer();
      } else {
        btn.textContent = '▶';
        if (timer) clearInterval(timer);
      }
    }

    // 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="4:3">
  <link rel="stylesheet" href="{{VENDOR_CDN}}/katex.min.css">
  <script src="{{VENDOR_CDN}}/katex.min.js"></script>
  <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;
      padding: 16px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }

    .main-wrap {
      width: 100%;
      max-width: 520px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      align-items: center;
    }

    /* Mode switcher */
    .toggle-bar {
      display: inline-flex;
      background: #f1f5f9;
      padding: 3px;
      border-radius: 20px;
      border: 1px solid #e2e8f0;
      margin-bottom: 2px;
    }
    .toggle-btn {
      border: none;
      background: transparent;
      padding: 5px 14px;
      font-size: 13px;
      font-weight: 600;
      border-radius: 16px;
      cursor: pointer;
      color: #64748b;
      transition: all 0.2s ease;
    }
    .toggle-btn.active {
      background: #ffffff;
      color: #0f172a;
      box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }

    /* Top Conditional Statement Box */
    .top-statement {
      width: 100%;
      background: #f8fafc;
      border: 2px solid #cbd5e1;
      border-radius: 12px;
      padding: 10px 14px;
      text-align: center;
      font-weight: 700;
      font-size: 15px;
      color: #0f172a;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
    }

    .tag-if { color: #16a34a; }
    .tag-then { color: #2563eb; }

    /* Columns container */
    .columns-row {
      width: 100%;
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
    }

    /* Cards */
    .panel-card {
      background: #ffffff;
      border-radius: 12px;
      padding: 12px 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      position: relative;
    }

    .panel-card.hypothesis {
      border: 2px solid #22c55e;
      background: #f0fdf4;
    }

    .panel-card.conclusion {
      border: 2px solid #3b82f6;
      background: #eff6ff;
    }

    .card-title {
      font-size: 14px;
      font-weight: 800;
      margin-bottom: 4px;
    }
    .hypothesis .card-title { color: #15803d; }
    .conclusion .card-title { color: #1d4ed8; }

    .card-symbol {
      font-size: 13px;
      font-weight: 600;
      color: #475569;
      margin-bottom: 6px;
      min-height: 20px;
    }

    .arrow-down {
      font-size: 16px;
      line-height: 1;
      margin: 4px 0;
      opacity: 0.6;
    }
    .hypothesis .arrow-down { color: #16a34a; }
    .conclusion .arrow-down { color: #2563eb; }

    .proof-role {
      width: 100%;
      background: #ffffff;
      border-radius: 8px;
      padding: 8px 6px;
      font-size: 12px;
      font-weight: 700;
      box-shadow: 0 1px 2px rgba(0,0,0,0.05);
    }
    .hypothesis .proof-role {
      border: 1px solid #bbf7d0;
      color: #166534;
    }
    .conclusion .proof-role {
      border: 1px solid #bfdbfe;
      color: #1e40af;
    }
    .role-sub {
      font-size: 11px;
      font-weight: 500;
      color: #64748b;
      margin-top: 2px;
    }

    /* Bottom Summary Pill */
    .summary-pill {
      width: 100%;
      background: #faf5ff;
      border: 1.5px solid #a855f7;
      border-radius: 12px;
      padding: 10px 12px;
      display: flex;
      flex-direction: column;
      gap: 6px;
      align-items: center;
      text-align: center;
    }

    .summary-header {
      font-size: 12px;
      font-weight: 800;
      color: #7e22ce;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }

    .summary-flow {
      display: flex;
      align-items: center;
      justify-content: center;
      flex-wrap: wrap;
      gap: 6px;
      font-size: 13px;
      font-weight: 600;
      color: #3b0764;
    }

    .flow-badge {
      background: #ffffff;
      border: 1px solid #e9d5ff;
      padding: 3px 8px;
      border-radius: 6px;
      white-space: nowrap;
    }
    .flow-badge.start { color: #15803d; border-color: #bbf7d0; }
    .flow-badge.deduction { color: #7e22ce; border-color: #d8b4fe; }
    .flow-badge.target { color: #1d4ed8; border-color: #bfdbfe; }

    .flow-arrow {
      color: #a855f7;
      font-weight: 700;
      font-size: 13px;
    }

    @media (max-width: 400px) {
      body { padding: 10px; }
      .top-statement { font-size: 13.5px; padding: 8px 10px; }
      .card-title { font-size: 13px; }
      .proof-role { font-size: 11px; }
      .role-sub { font-size: 10px; }
      .summary-flow { font-size: 12px; }
    }
  </style>
</head>
<body>
  <div class="main-wrap">
    
    <div class="toggle-bar">
      <button class="toggle-btn active" id="btnLogic">General Logic</button>
      <button class="toggle-btn" id="btnGeom">Geometry Example</button>
    </div>

    
    <div class="top-statement" id="topStatement">
      <span class="tag-if">If <span id="labelP">p</span>,</span>
      <span class="tag-then">then <span id="labelQ">q</span></span>
      <span style="color:#64748b; font-weight:450; font-size: 13px; margin-left: 4px;" id="formulaPtoQ"></span>
    </div>

    
    <div class="columns-row">
      
      <div class="panel-card hypothesis">
        <div class="card-title">Hypothesis (<span id="hypSym">p</span>)</div>
        <div class="card-symbol" id="hypDetail">Premise / Condition</div>
        <div class="arrow-down">↓</div>
        <div class="proof-role">
          <div id="hypRole">Given</div>
          <div class="role-sub" id="hypRoleSub">Starting Information</div>
        </div>
      </div>

      
      <div class="panel-card conclusion">
        <div class="card-title">Conclusion (<span id="conSym">q</span>)</div>
        <div class="card-symbol" id="conDetail">Result / Consequence</div>
        <div class="arrow-down">↓</div>
        <div class="proof-role">
          <div id="conRole">To Prove</div>
          <div class="role-sub" id="conRoleSub">Target Statement</div>
        </div>
      </div>
    </div>

    
    <div class="summary-pill">
      <div class="summary-header">Direct Proof Structure (Modus Ponens)</div>
      <div class="summary-flow">
        <span class="flow-badge start" id="flowStart">Given <i>p</i> is true</span>
        <span class="flow-arrow">→</span>
        <span class="flow-badge deduction" id="flowMid">Logical deduction</span>
        <span class="flow-arrow">→</span>
        <span class="flow-badge target" id="flowEnd"><i>q</i> is proved</span>
      </div>
    </div>
  </div>

  <script>
    const data = {
      logic: {
        p: 'p',
        q: 'q',
        formula: '(p \\implies q)',
        hypDetail: 'Premise / Condition',
        hypRole: 'Given',
        hypRoleSub: 'Starting Information',
        conDetail: 'Result / Consequence',
        conRole: 'To Prove',
        conRoleSub: 'Target Statement',
        flowStart: 'Given <i>p</i> is true',
        flowMid: 'Logical deduction',
        flowEnd: '<i>q</i> is proved'
      },
      geom: {
        p: 'lines are ∥',
        q: 'alt. angles are =',
        formula: '(L_1 \\parallel L_2 \\implies \\angle 1 = \\angle 2)',
        hypDetail: 'Line A ∥ Line B',
        hypRole: 'Given',
        hypRoleSub: 'AB ∥ CD',
        conDetail: '∠1 ≅ ∠2',
        conRole: 'To Prove',
        conRoleSub: '∠1 = ∠2',
        flowStart: 'Given <i>AB ∥ CD</i>',
        flowMid: 'Parallel Postulate',
        flowEnd: '∠1 ≅ ∠2 Proved'
      }
    };

    function renderMode(mode) {
      const d = data[mode];
      document.getElementById('labelP').textContent = d.p;
      document.getElementById('labelQ').textContent = d.q;
      document.getElementById('hypSym').textContent = mode === 'logic' ? 'p' : 'p';
      document.getElementById('conSym').textContent = mode === 'logic' ? 'q' : 'q';
      document.getElementById('hypDetail').textContent = d.hypDetail;
      document.getElementById('conDetail').textContent = d.conDetail;
      document.getElementById('hypRole').textContent = d.hypRole;
      document.getElementById('hypRoleSub').textContent = d.hypRoleSub;
      document.getElementById('conRole').textContent = d.conRole;
      document.getElementById('conRoleSub').textContent = d.conRoleSub;
      document.getElementById('flowStart').innerHTML = d.flowStart;
      document.getElementById('flowMid').textContent = d.flowMid;
      document.getElementById('flowEnd').innerHTML = d.flowEnd;

      if (window.katex) {
        katex.render(d.formula, document.getElementById('formulaPtoQ'), { throwOnError: false });
      }
    }

    const btnLogic = document.getElementById('btnLogic');
    const btnGeom = document.getElementById('btnGeom');

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      btnGeom.classList.remove('active');
      renderMode('logic');
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      btnGeom.classList.add('active');
      btnLogic.classList.remove('active');
      renderMode('geom');
    });

    renderMode('logic');
  </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">
  <title>Conditional Statement Breakdown</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }
    body {
      background: transparent;
      color: #1e293b;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 16px;
      min-height: 100%;
    }
    .diagram {
      width: 100%;
      max-width: 580px;
      display: flex;
      flex-direction: column;
      gap: 14px;
    }
    /* Formula Banner */
    .formula-bar {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 16px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px 16px;
      font-size: 17px;
      font-weight: 700;
    }
    .var-p { color: #16a34a; }
    .var-q { color: #2563eb; }
    .divider { color: #cbd5e1; font-weight: 300; }

    /* Statement Card */
    .sentence-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 14px;
      padding: 18px 14px;
      box-shadow: 0 4px 12px rgba(0, 0, 0, 0.03);
      display: flex;
      flex-direction: column;
      gap: 16px;
    }

    /* Main Sentence Display */
    .sentence-flow {
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      justify-content: center;
      gap: 6px 4px;
      font-size: 16px;
      font-weight: 600;
      text-align: center;
    }

    .cue {
      color: #64748b;
      background: #f1f5f9;
      padding: 5px 8px;
      border-radius: 6px;
      border: 1px dashed #cbd5e1;
      font-weight: 600;
    }

    .clause {
      padding: 6px 10px;
      border-radius: 8px;
      transition: all 0.2s ease;
    }

    .hyp-box {
      background: #f0fdf4;
      border: 1.5px solid #22c55e;
      color: #15803d;
    }

    .con-box {
      background: #eff6ff;
      border: 1.5px solid #3b82f6;
      color: #1d4ed8;
    }

    /* Badges & Arrows */
    .badge-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
    }

    .badge-col {
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 4px;
    }

    .arrow {
      font-size: 16px;
      font-weight: 900;
      line-height: 1;
    }
    .arrow-p { color: #16a34a; }
    .arrow-q { color: #2563eb; }

    .role-badge {
      width: 100%;
      text-align: center;
      padding: 8px 10px;
      border-radius: 10px;
      font-size: 13px;
      font-weight: 700;
      display: flex;
      flex-direction: column;
      gap: 2px;
    }

    .badge-p {
      background: #22c55e;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(34, 197, 94, 0.25);
    }
    .badge-p span {
      font-size: 11px;
      font-weight: 500;
      opacity: 0.95;
    }

    .badge-q {
      background: #2563eb;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(37, 99, 235, 0.25);
    }
    .badge-q span {
      font-size: 11px;
      font-weight: 500;
      opacity: 0.95;
    }

    /* Notice callout */
    .cue-notice {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 10px;
      text-align: center;
    }

    /* Interactive Switcher */
    .switcher {
      display: flex;
      justify-content: center;
      gap: 8px;
    }

    .switch-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      color: #475569;
      padding: 5px 12px;
      border-radius: 20px;
      font-size: 12px;
      font-weight: 600;
      cursor: pointer;
      transition: all 0.2s ease;
    }

    .switch-btn.active {
      background: #0f172a;
      border-color: #0f172a;
      color: #ffffff;
    }

    @media (max-width: 420px) {
      .formula-bar { font-size: 15px; gap: 10px; }
      .sentence-flow { font-size: 14px; }
      .role-badge { font-size: 12px; padding: 6px; }
      .cue-notice { font-size: 11px; }
    }
  </style>
</head>
<body>
  <div class="diagram">
    
    <div class="formula-bar">
      <span>If <span class="var-p">p</span>, then <span class="var-q">q</span></span>
      <span class="divider">|</span>
      <span><span class="var-p">p</span> &rarr; <span class="var-q">q</span></span>
    </div>

    
    <div class="sentence-card">
      <div class="sentence-flow">
        <span class="cue">If</span>
        <span id="hypText" class="clause hyp-box">a polygon has 3 sides</span>
        <span class="cue">, then</span>
        <span id="conText" class="clause con-box">it is a triangle</span>
      </div>

      
      <div class="badge-grid">
        <div class="badge-col">
          <div class="arrow arrow-p">&uarr;</div>
          <div class="role-badge badge-p">
            Hypothesis (p)
            <span id="hypSub">"a polygon has 3 sides"</span>
          </div>
        </div>
        <div class="badge-col">
          <div class="arrow arrow-q">&uarr;</div>
          <div class="role-badge badge-q">
            Conclusion (q)
            <span id="conSub">"it is a triangle"</span>
          </div>
        </div>
      </div>

      
      <div class="cue-notice">
        <span>✦</span>
        <span><b>Notice:</b> <em>If</em> and <em>Then</em> are cue words, not part of <b>p</b> or <b>q</b></span>
      </div>
    </div>

    
    <div class="switcher">
      <button class="switch-btn active" onclick="setExample(0)">Example 1: Geometry</button>
      <button class="switch-btn" onclick="setExample(1)">Example 2: Weather</button>
    </div>
  </div>

  <script>
    const examples = [
      {
        p: "a polygon has 3 sides",
        q: "it is a triangle"
      },
      {
        p: "it rains outside",
        q: "the grass gets wet"
      }
    ];

    function setExample(index) {
      const btns = document.querySelectorAll('.switch-btn');
      btns.forEach((btn, i) => {
        btn.classList.toggle('active', i === index);
      });

      const data = examples[index];
      document.getElementById('hypText').textContent = data.p;
      document.getElementById('conText').textContent = data.q;
      document.getElementById('hypSub').textContent = `"${data.p}"`;
      document.getElementById('conSub').textContent = `"${data.q}"`;
    }
  </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;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 10px;
    }

    .header-bar {
      text-align: center;
      margin-bottom: 4px;
    }

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

    .frames-container {
      display: flex;
      flex-direction: row;
      align-items: center;
      justify-content: center;
      gap: 12px;
      width: 100%;
      max-width: 620px;
    }

    .frame-wrapper {
      flex: 1;
      max-width: 280px;
      display: flex;
      flex-direction: column;
      align-items: center;
    }

    .frame-title {
      font-size: 13px;
      font-weight: 700;
      color: #475569;
      margin-bottom: 4px;
    }

    svg {
      width: 100%;
      height: auto;
      display: block;
      border-radius: 8px;
      background: #f8fafc;
      box-shadow: 0 0 0 1px #e2e8f0;
      user-select: none;
    }

    .tri {
      fill: #fb923c;
      stroke: #ea580c;
      stroke-width: 1.5;
      transition: fill 0.3s ease, opacity 0.3s ease;
    }

    .sq-c {
      fill: #bbf7d0;
      stroke: #16a34a;
      stroke-width: 2;
      transition: fill 0.3s ease, opacity 0.3s ease;
    }

    .sq-a {
      fill: #fecaca;
      stroke: #dc2626;
      stroke-width: 2;
      transition: fill 0.3s ease, opacity 0.3s ease;
    }

    .sq-b {
      fill: #bfdbfe;
      stroke: #2563eb;
      stroke-width: 2;
      transition: fill 0.3s ease, opacity 0.3s ease;
    }

    .lbl {
      font-size: 12px;
      font-weight: 800;
      text-anchor: middle;
      dominant-baseline: central;
      pointer-events: none;
    }

    .dim-lbl {
      font-size: 10px;
      font-weight: 700;
      fill: #64748b;
      text-anchor: middle;
      dominant-baseline: central;
    }

    .lbl-c { fill: #15803d; font-size: 14px; }
    .lbl-a { fill: #b91c1c; font-size: 13px; }
    .lbl-b { fill: #1d4ed8; font-size: 14px; }
    .lbl-tri { fill: #c2410c; font-size: 9px; font-weight: 700; opacity: 0.85; }

    .equals-sign {
      font-size: 24px;
      font-weight: 800;
      color: #0f172a;
      padding-top: 18px;
    }

    .controls {
      display: flex;
      gap: 6px;
      margin: 8px 0 6px;
      background: #f1f5f9;
      padding: 3px;
      border-radius: 8px;
    }

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

    .btn.active {
      background: #ffffff;
      color: #0f172a;
      box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }

    .conclusion-bar {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 15px;
      font-weight: 700;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      padding: 6px 16px;
      border-radius: 8px;
      color: #1e2945;
    }

    .pill-c { color: #16a34a; background: #dcfce7; padding: 2px 8px; border-radius: 4px; }
    .pill-a { color: #dc2626; background: #fee2e2; padding: 2px 8px; border-radius: 4px; }
    .pill-b { color: #2563eb; background: #dbeafe; padding: 2px 8px; border-radius: 4px; }

    /* Interactive state highlighting */
    body.mode-tri .sq-c, body.mode-tri .sq-a, body.mode-tri .sq-b { opacity: 0.25; }
    body.mode-area .tri { opacity: 0.25; }
    body.mode-area .lbl-tri { opacity: 0.1; }
  </style>
</head>
<body>

  <div class="header-bar">
    <div class="subtitle">Total Frame Area − 4 Triangles = Uncovered Area</div>
  </div>

  <div class="frames-container">
    
    <div class="frame-wrapper">
      <div class="frame-title">Square of Side (a + b)</div>
      <svg viewBox="0 0 180 180">
        
        
        <polygon class="sq-c" points="110,15 165,110 70,165 15,70" />
        <text x="90" y="90" class="lbl lbl-c">c²</text>

        
        
        <polygon class="tri" points="15,15 110,15 15,70" />
        <text x="42" y="32" class="lbl lbl-tri">½ab</text>

        
        <polygon class="tri" points="165,15 165,110 110,15" />
        <text x="148" y="42" class="lbl lbl-tri">½ab</text>

        
        <polygon class="tri" points="165,165 70,165 165,110" />
        <text x="138" y="148" class="lbl lbl-tri">½ab</text>

        
        <polygon class="tri" points="15,165 15,70 70,165" />
        <text x="32" y="138" class="lbl lbl-tri">½ab</text>

        
        <text x="62" y="7" class="dim-lbl">b</text>
        <text x="137" y="7" class="dim-lbl">a</text>
        <text x="7" y="42" class="dim-lbl">a</text>
        <text x="7" y="117" class="dim-lbl">b</text>
        <text x="72" y="48" class="dim-lbl" style="fill:#16a34a; font-weight:800;">c</text>
      </svg>
    </div>

    <div class="equals-sign">=</div>

    
    <div class="frame-wrapper">
      <div class="frame-title">Same Square (a + b)</div>
      <svg viewBox="0 0 180 180">
        
        <rect class="sq-a" x="15" y="15" width="55" height="55" />
        <text x="42.5" y="42.5" class="lbl lbl-a">a²</text>

        
        <rect class="sq-b" x="70" y="70" width="95" height="95" />
        <text x="117.5" y="117.5" class="lbl lbl-b">b²</text>

        
        <polygon class="tri" points="70,15 165,15 165,70" />
        <text x="135" y="32" class="lbl lbl-tri">½ab</text>
        <polygon class="tri" points="70,15 165,70 70,70" />
        <text x="100" y="52" class="lbl lbl-tri">½ab</text>

        
        <polygon class="tri" points="15,70 70,70 15,165" />
        <text x="32" y="100" class="lbl lbl-tri">½ab</text>
        <polygon class="tri" points="70,70 70,165 15,165" />
        <text x="52" y="135" class="lbl lbl-tri">½ab</text>

        
        <text x="42.5" y="7" class="dim-lbl">a</text>
        <text x="117.5" y="7" class="dim-lbl">b</text>
        <text x="7" y="42.5" class="dim-lbl">a</text>
        <text x="7" y="117.5" class="dim-lbl">b</text>
      </svg>
    </div>
  </div>

  
  <div class="controls">
    <button class="btn active" onclick="setMode('all', this)">All</button>
    <button class="btn" onclick="setMode('tri', this)">4 Triangles</button>
    <button class="btn" onclick="setMode('area', this)">Uncovered Area</button>
  </div>

  
  <div class="conclusion-bar">
    <span class="pill-c">c²</span>
    <span>=</span>
    <span class="pill-a">a²</span>
    <span>+</span>
    <span class="pill-b">b²</span>
  </div>

  <script>
    function setMode(mode, btn) {
      document.body.className = mode === 'all' ? '' : 'mode-' + mode;
      document.querySelectorAll('.btn').forEach(b => b.classList.remove('active'));
      btn.classList.add('active');
    }
  </script>
</body>
</html>

Visual and Algebraic Proofs of the Pythagorean Theorem

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <title>Pythagorean Theorem Visual Proof</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, 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;
    }

    .header-math {
      height: 38px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 700;
      font-size: 17px;
      color: #0f172a;
      letter-spacing: 0.2px;
    }
    .header-math span {
      transition: all 0.3s ease;
    }
    .hl-blue { color: #0284c7; }
    .hl-amber { color: #d97706; }
    .hl-green { color: #16a34a; }

    .diagram-stage {
      position: relative;
      width: 100%;
      max-width: 320px;
      aspect-ratio: 1 / 1;
      margin: 4px 0;
    }

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

    .grid-line {
      stroke: #e2e8f0;
      stroke-width: 1;
    }

    .tri-path {
      fill: #0284c7;
      fill-opacity: 0;
      stroke: #0284c7;
      stroke-width: 2;
      stroke-dasharray: 60;
      stroke-dashoffset: 60;
      transition: all 0.5s ease;
    }

    .inner-square {
      fill: #f59e0b;
      fill-opacity: 0;
      stroke: #d97706;
      stroke-width: 2.5;
      stroke-dasharray: 100;
      stroke-dashoffset: 100;
      transition: all 0.5s ease;
    }

    .dim-label {
      font-size: 13px;
      font-weight: 700;
      fill: #475569;
      opacity: 0;
      transition: opacity 0.3s ease;
      text-anchor: middle;
      dominant-baseline: central;
    }

    .center-label {
      font-size: 15px;
      font-weight: 800;
      fill: #b45309;
      opacity: 0;
      transition: opacity 0.3s ease;
      text-anchor: middle;
      dominant-baseline: central;
    }

    .tri-area-label {
      font-size: 11px;
      font-weight: 700;
      fill: #0369a1;
      opacity: 0;
      transition: opacity 0.3s ease;
      text-anchor: middle;
      dominant-baseline: central;
    }

    .step-2 .tri-path {
      fill-opacity: 0.18;
      stroke-dashoffset: 0;
    }
    .step-2 .tri-area-label,
    .step-2 .dim-label {
      opacity: 1;
    }

    .step-3 .tri-path,
    .step-4 .tri-path {
      fill-opacity: 0.12;
      stroke-dashoffset: 0;
    }
    .step-3 .tri-area-label,
    .step-4 .tri-area-label {
      opacity: 0.4;
    }
    .step-3 .dim-label,
    .step-4 .dim-label {
      opacity: 1;
    }

    .step-3 .inner-square,
    .step-4 .inner-square {
      fill-opacity: 0.22;
      stroke-dashoffset: 0;
    }
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Identifying Adjacent, Complementary, and Supplementary Angles

Finding Unknown Angles Using Complementary and Supplementary Rules

Vertical Angles and Linear Pairs

Solving Linear Equations with Intersecting Lines and Angle Pairs

Parallel Lines and Transversals: Alternate Interior and Exterior Angles

Alternate, Corresponding, and Co-Interior Angles on Parallel Lines

Solving Multi-Step Algebraic Equations with Parallel Lines and Transversals

Proving Lines Are Parallel Using Angle Relationships

Combining Parallel Line Rules with Triangles and Quadrilaterals

math

Angle Relationships and Parallel Lines

Triangle Angle Sum Theorem: Proof and Applications

Exterior Angle Theorem of Triangles

Solving Algebraic Equations with Triangle Angles

Base Angles Theorem: Isosceles Triangle Properties

Equilateral and Equiangular Triangle Properties

Applying the Triangle Inequality Theorem to Solve Problems

Relationships Between Side Lengths and Opposite Angles in Triangles

Triangle Theorems, Angles, and Inequalities

Side-Side-Side (SSS) Triangle Congruence

Side-Angle-Side (SAS) Triangle Congruence

Angle-Side-Angle (ASA) and Angle-Angle-Side (AAS) Congruence

Hypotenuse-Leg (HL) Congruence for Right Triangles

Why AAA and SSA Do Not Guarantee Triangle Congruence

Writing Two-Column and Paragraph Proofs for Congruent Triangles

Triangle Congruence Criteria and Proofs

Deriving the Pythagorean Theorem Using Similar Triangles

Calculating the Hypotenuse of a Right Triangle

Calculating an Unknown Leg of a Right Triangle

Identifying Pythagorean Triples

Classifying Acute, Right, and Obtuse Triangles Using Side Lengths

Finding Distances on the Coordinate Plane Using Pythagoras

Calculating Perimeter and Area of Composite Right Triangles

Solving 3D Pythagorean Problems in Boxes and Cones

The Pythagorean Theorem and Right Triangle Geometry

Classifying Quadrilaterals: Squares, Rectangles, Parallelograms, and Rhombuses

Properties and Proofs of Parallelograms

Special Parallelograms: Rhombuses, Rectangles, and Squares

Trapezoids, Isosceles Trapezoids, and Kites

Interior and Exterior Angles of Convex Polygons

Angles and Side Properties of Regular Polygons

Designing Decision Tree Algorithms to Classify Polygons

Quadrilaterals, Polygons, and Angle Sums

Converse, Inverse, and Contrapositive Statements

Definitions and Biconditional Statements in Geometry

Inductive Versus Deductive Reasoning

Disproving Conjectures with Counterexamples

Proving Angle Relationships with Parallel Lines

Direct Synthetic Proofs in Plane Geometry

Indirect Proof and Proof by Contradiction

Deductive Reasoning, Logic, and Geometric Proofs

Defining Circles, Radii, Diameters, and Pi

Calculating Circumference Using Exact and Approximate Values of Pi

Central Angles and Arc Measure

Calculating Arc Length as a Fraction of Circumference

Chords and Perpendicular Bisector Properties in Circles

Tangent Lines and Radius Perpendicularity

Equal Tangents from an External Point: Theorem and Proof

Inscribed Angle Theorem and Corollaries

Angles Formed by Tangents, Secants, and Chords

Circle Foundations, Pi, Circumference, and Arcs

定义、命题、定理与推论：数学语言的严格界定与层级关系

命题的结构：区分条件与结论并改写为"如果……那么……"标准形式

原命题与逆命题：互逆命题的构造与真假性独立分析

反例的作用：满足条件但不满足结论的实例与假命题驳斥

定义、命题、定理与反例

证明的意义与必要性：从直觉误区、测量局限到严密逻辑推理

综合法的证明格式："因为……所以……"的规范三段论推导

反证法的含义与逻辑架构：假设不成立、导出矛盾与肯定原结论

反证法的经典应用：证明两直线平行、角不等与无理数命题

数学证明方法：综合法与反证法

OGM.8.GEO.6

OGM.8.GEO.6

Aligned learning resources

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