<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Linear Function vs Simple Interest Model</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #f8f9fa;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100vh;
    }
    .diagram-grid {
      display: grid;
      grid-template-columns: 1fr 1.25fr;
      gap: 20px;
      width: 100%;
      max-width: 660px;
      align-items: center;
    }
    @media (max-width: 540px) {
      .diagram-grid {
        grid-template-columns: 1fr;
        gap: 16px;
      }
    }
    .panel {
      background: transparent;
      padding: 4px;
    }
    .eq-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      gap: 6px;
      padding-bottom: 10px;
      border-bottom: 1.5px solid #e2e8f0;
      margin-bottom: 12px;
    }
    .eq-box {
      font-family: "Courier New", Courier, monospace;
      font-size: 13px;
      font-weight: 700;
      background: #eef2f6;
      color: #0f172a;
      padding: 5px 8px;
      border-radius: 6px;
      letter-spacing: 0.3px;
      white-space: nowrap;
    }
    .eq-arrow {
      color: #64748b;
      font-size: 14px;
      font-weight: bold;
    }
    .mapping-list {
      display: flex;
      flex-direction: column;
      gap: 10px;
    }
    .map-item {
      padding: 8px 10px;
      background: rgba(255, 255, 255, 0.7);
      border-radius: 6px;
      border-left: 3.5px solid transparent;
    }
    .map-item.slope-item {
      border-left-color: #0284c7;
    }
    .map-item.intercept-item {
      border-left-color: #7c3aed;
    }
    .map-title {
      font-size: 13px;
      font-weight: 700;
      display: flex;
      justify-content: space-between;
      margin-bottom: 2px;
    }
    .slope-color { color: #0284c7; }
    .intercept-color { color: #7c3aed; }
    .map-desc {
      font-size: 12px;
      color: #475569;
      font-weight: 500;
      line-height: 1.3;
    }
    .current-val {
      margin-top: 12px;
      padding: 8px 10px;
      background: #ecfdf5;
      border-left: 3.5px solid #10b981;
      border-radius: 6px;
      font-size: 12px;
      font-weight: 600;
      color: #065f46;
      line-height: 1.4;
    }
    .graph-container {
      position: relative;
      width: 100%;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }
    .axis { stroke: #64748b; stroke-width: 1.5; stroke-linecap: round; }
    .grid { stroke: #e2e8f0; stroke-width: 1; stroke-dasharray: 3 3; }
    .axis-label { fill: #1e2945; font-size: 10px; font-weight: 700; }
    .tick-label { fill: #475569; font-size: 9px; font-weight: 600; font-family: system-ui, sans-serif; }
    .stair-fill { fill: rgba(2, 132, 199, 0.08); }
    .stair-line { fill: none; stroke: #0284c7; stroke-width: 1.5; stroke-dasharray: 3 3; }
    .step-tag { fill: #0284c7; font-size: 8px; font-weight: 700; font-family: system-ui, sans-serif; }
    .plot-line { fill: none; stroke: #0284c7; stroke-width: 2.5; stroke-linecap: round; }
    .data-point {
      fill: #ffffff;
      stroke: #0284c7;
      stroke-width: 2.5;
      cursor: pointer;
      transition: r 0.15s ease, fill 0.15s ease;
    }
    .data-point.active {
      fill: #0284c7;
      stroke: #0369a1;
      r: 6;
    }
    .step-controls {
      display: flex;
      justify-content: center;
      flex-wrap: wrap;
      gap: 5px;
      margin-top: 10px;
      width: 100%;
    }
    .step-btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 4px 8px;
      font-size: 11px;
      font-weight: 600;
      border-radius: 4px;
      cursor: pointer;
      transition: background 0.15s, border-color 0.15s, color 0.15s;
    }
    .step-btn.active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
    }
  </style>
</head>
<body>

  <div class="diagram-grid">
    
    <div class="panel">
      <div class="eq-header">
        <span class="eq-box">y = mx + b</span>
        <span class="eq-arrow">⟷</span>
        <span class="eq-box">A(t) = (Pr)t + P</span>
      </div>

      <div class="mapping-list">
        <div class="map-item slope-item">
          <div class="map-title">
            <span class="slope-color">Slope m = Pr</span>
            <span class="slope-color">+$50 / yr</span>
          </div>
          <div class="map-desc">Constant dollar growth per year</div>
        </div>

        <div class="map-item intercept-item">
          <div class="map-title">
            <span class="intercept-color">Y-intercept b = P</span>
            <span class="intercept-color">$1,000</span>
          </div>
          <div class="map-desc">Initial deposit at t = 0</div>
        </div>
      </div>

      <div id="statusBox" class="current-val">
        Selected t = 0 yr : A(0) = $1,000
      </div>
    </div>

    
    <div class="panel graph-container">
      <svg viewBox="0 0 300 215">
        
        
        <line x1="48" y1="170" x2="285" y2="170" class="grid" />
        <line x1="48" y1="144" x2="285" y2="144" class="grid" />
        <line x1="48" y1="118" x2="285" y2="118" class="grid" />
        <line x1="48" y1="92" x2="285" y2="92" class="grid" />
        <line x1="48" y1="66" x2="285" y2="66" class="grid" />
        <line x1="48" y1="40" x2="285" y2="40" class="grid" />

        
        
        <line x1="55" y1="35" x2="55" y2="170" class="grid" />
        <line x1="100" y1="35" x2="100" y2="170" class="grid" />
        <line x1="145" y1="35" x2="145" y2="170" class="grid" />
        <line x1="190" y1="35" x2="190" y2="170" class="grid" />
        <line x1="235" y1="35" x2="235" y2="170" class="grid" />
        <line x1="280" y1="35" x2="280" y2="170" class="grid" />

        
        <g id="stairs">
          
          <polygon points="55,170 100,170 100,144" class="stair-fill" />
          <path d="M 55 170 L 100 170 L 100 144" class="stair-line" />
          <text x="103" y="160" class="step-tag">+$50</text>

          
          <polygon points="100,144 145,144 145,118" class="stair-fill" />
          <path d="M 100 144 L 145 144 L 145 118" class="stair-line" />
          <text x="148" y="134" class="step-tag">+$50</text>

          
          <polygon points="145,118 190,118 190,92" class="stair-fill" />
          <path d="M 145 118 L 190 118 L 190 92" class="stair-line" />
          <text x="193" y="108" class="step-tag">+$50</text>

          
          <polygon points="190,92 235,92 235,66" class="stair-fill" />
          <path d="M 190 92 L 235 92 L 235,66" class="stair-line" />
          <text x="238" y="82" class="step-tag">+$50</text>

          
          <polygon points="235,66 280,66 280,40" class="stair-fill" />
          <path d="M 235 66 L 280 66 L 280 40" class="stair-line" />
        </g>

        
        <line x1="55" y1="170" x2="280" y2="40" class="plot-line" />

        
        <line x1="48" y1="170" x2="290" y2="170" class="axis" />
        <line x1="55" y1="175" x2="55" y2="30" class="axis" />

        
        <text x="55" y="184" class="tick-label" text-anchor="middle">0</text>
        <text x="100" y="184" class="tick-label" text-anchor="middle">1</text>
        <text x="145" y="184" class="tick-label" text-anchor="middle">2</text>
        <text x="190" y="184" class="tick-label" text-anchor="middle">3</text>
        <text x="235" y="184" class="tick-label" text-anchor="middle">4</text>
        <text x="280" y="184" class="tick-label" text-anchor="middle">5</text>

        
        <text x="45" y="173" class="tick-label" text-anchor="end">$1,000</text>
        <text x="45" y="147" class="tick-label" text-anchor="end">$1,050</text>
        <text x="45" y="121" class="tick-label" text-anchor="end">$1,100</text>
        <text x="45" y="95" class="tick-label" text-anchor="end">$1,150</text>
        <text x="45" y="69" class="tick-label" text-anchor="end">$1,200</text>
        <text x="45" y="43" class="tick-label" text-anchor="end">$1,250</text>

        
        <text x="167" y="202" class="axis-label" text-anchor="middle">Time t (years)</text>
        <text x="12" y="20" class="axis-label" text-anchor="start">Total Amount A(t) ($)</text>

        
        <circle id="pt0" cx="55" cy="170" r="4.5" class="data-point active" onclick="setYear(0)" />
        <circle id="pt1" cx="100" cy="144" r="4.5" class="data-point" onclick="setYear(1)" />
        <circle id="pt2" cx="145" cy="118" r="4.5" class="data-point" onclick="setYear(2)" />
        <circle id="pt3" cx="190" cy="92" r="4.5" class="data-point" onclick="setYear(3)" />
        <circle id="pt4" cx="235" cy="66" r="4.5" class="data-point" onclick="setYear(4)" />
        <circle id="pt5" cx="280" cy="40" r="4.5" class="data-point" onclick="setYear(5)" />
      </svg>

      
      <div class="step-controls">
        <button class="step-btn active" id="btn0" onclick="setYear(0)">t = 0</button>
        <button class="step-btn" id="btn1" onclick="setYear(1)">t = 1</button>
        <button class="step-btn" id="btn2" onclick="setYear(2)">t = 2</button>
        <button class="step-btn" id="btn3" onclick="setYear(3)">t = 3</button>
        <button class="step-btn" id="btn4" onclick="setYear(4)">t = 4</button>
        <button class="step-btn" id="btn5" onclick="setYear(5)">t = 5</button>
      </div>
    </div>
  </div>

  <script>
    const data = [
      { t: 0, amount: 1000 },
      { t: 1, amount: 1050 },
      { t: 2, amount: 1100 },
      { t: 3, amount: 1150 },
      { t: 4, amount: 1200 },
      { t: 5, amount: 1250 }
    ];

    function setYear(year) {
      for (let i = 0; i <= 5; i++) {
        const btn = document.getElementById('btn' + i);
        const pt = document.getElementById('pt' + i);
        if (i === year) {
          btn.classList.add('active');
          pt.classList.add('active');
        } else {
          btn.classList.remove('active');
          pt.classList.remove('active');
        }
      }

      const info = data[year];
      const statusBox = document.getElementById('statusBox');
      statusBox.innerHTML = `At t = ${info.t} yr : A(${info.t}) = (50 &times; ${info.t}) + 1,000 = <strong>$${info.amount.toLocaleString()}</strong>`;
    }
  </script>
</body>
</html>

Modeling Simple Interest as Linear Growth

<!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 {
      background: #f8f9fa;
      color: #1e2945;
      display: flex;
      justify-content: center;
      align-items: center;
      padding: 12px;
      min-height: 100%;
    }

    .diagram {
      width: 100%;
      max-width: 580px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    /* Formula Header */
    .formula-bar {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 28px;
      font-weight: 800;
      padding: 6px 0;
    }

    .sym {
      padding: 2px 10px;
      border-radius: 8px;
      line-height: 1.2;
    }

    .op {
      color: #94a3b8;
      font-weight: 600;
      font-size: 24px;
    }

    /* Color definitions */
    .c-blue {
      background: #e0e7ff;
      color: #1e3a8a;
      border: 1px solid #93c5fd;
    }
    .c-green {
      background: #ecfdf5;
      color: #065f46;
      border: 1px solid #6ee7b7;
    }
    .c-amber {
      background: #fffbeb;
      color: #92400e;
      border: 1px solid #fcd34d;
    }
    .c-purple {
      background: #f5f3ff;
      color: #5b21b6;
      border: 1px solid #c4b5fd;
    }

    /* Variable Cards Grid */
    .cards-grid {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 8px;
    }

    @media (max-width: 460px) {
      .cards-grid {
        grid-template-columns: repeat(2, 1fr);
      }
      .formula-bar {
        font-size: 22px;
      }
    }

    .v-card {
      border-radius: 10px;
      padding: 10px 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      gap: 2px;
    }

    .v-var {
      font-size: 20px;
      font-weight: 800;
    }

    .v-title {
      font-size: 13px;
      font-weight: 700;
      line-height: 1.2;
    }

    .v-sub {
      font-size: 11px;
      opacity: 0.85;
      line-height: 1.2;
      margin-top: 2px;
    }

    /* Interactive Section */
    .interactive-panel {
      background: #ffffff;
      border: 1px solid #e6e6e6;
      border-radius: 12px;
      padding: 12px 14px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .controls-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 10px;
    }

    @media (max-width: 420px) {
      .controls-grid {
        grid-template-columns: 1fr;
        gap: 8px;
      }
    }

    .control-group {
      display: flex;
      flex-direction: column;
      gap: 4px;
    }

    .ctrl-label {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 12px;
      font-weight: 700;
    }

    .ctrl-tag {
      font-size: 11px;
      padding: 1px 6px;
      border-radius: 4px;
    }

    input[type=range] {
      width: 100%;
      height: 6px;
      border-radius: 3px;
      background: #e2e8f0;
      outline: none;
      -webkit-appearance: none;
      appearance: none;
    }

    input[type=range]::-webkit-slider-thumb {
      -webkit-appearance: none;
      width: 16px;
      height: 16px;
      border-radius: 50%;
      background: #1e2945;
      cursor: pointer;
      box-shadow: 0 1px 3px rgba(0,0,0,0.2);
    }

    /* Live Math Display */
    .calc-box {
      background: #f8f9fa;
      border: 1px dashed #cbd5e1;
      border-radius: 8px;
      padding: 10px;
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      justify-content: center;
      gap: 6px;
      font-size: 16px;
      font-weight: 700;
    }

    .math-pill {
      padding: 4px 8px;
      border-radius: 6px;
      font-size: 15px;
      font-weight: 800;
      display: inline-flex;
      align-items: center;
    }

    .growth-track {
      height: 10px;
      background: #ecfdf5;
      border: 1px solid #6ee7b7;
      border-radius: 5px;
      display: flex;
      overflow: hidden;
      margin-top: 2px;
    }

    .bar-p {
      background: #10b981;
      height: 100%;
    }

    .bar-i {
      background: #3b82f6;
      height: 100%;
      transition: width 0.2s ease;
    }

    .bar-legend {
      display: flex;
      justify-content: space-between;
      font-size: 11px;
      font-weight: 600;
      color: #64748b;
    }
  </style>
</head>
<body>

<div class="diagram">
  
  <div class="formula-bar">
    <span class="sym c-blue">I</span>
    <span class="op">=</span>
    <span class="sym c-green">P</span>
    <span class="op">·</span>
    <span class="sym c-amber">r</span>
    <span class="op">·</span>
    <span class="sym c-purple">t</span>
  </div>

  
  <div class="cards-grid">
    <div class="v-card c-blue">
      <div class="v-var">I</div>
      <div class="v-title">Interest</div>
      <div class="v-sub">Earned</div>
    </div>
    <div class="v-card c-green">
      <div class="v-var">P</div>
      <div class="v-title">Principal</div>
      <div class="v-sub">Starting $</div>
    </div>
    <div class="v-card c-amber">
      <div class="v-var">r</div>
      <div class="v-title">Rate</div>
      <div class="v-sub">Annual decimal</div>
    </div>
    <div class="v-card c-purple">
      <div class="v-var">t</div>
      <div class="v-title">Time</div>
      <div class="v-sub">In years</div>
    </div>
  </div>

  
  <div class="interactive-panel">
    <div class="controls-grid">
      
      <div class="control-group">
        <div class="ctrl-label">
          <span>Principal (P)</span>
          <span class="ctrl-tag c-green" id="valP">$1,000</span>
        </div>
        <input type="range" id="rangeP" min="500" max="2500" step="250" value="1000">
      </div>

      
      <div class="control-group">
        <div class="ctrl-label">
          <span>Rate (r)</span>
          <span class="ctrl-tag c-amber" id="valR">4% (0.04)</span>
        </div>
        <input type="range" id="rangeR" min="1" max="10" step="1" value="4">
      </div>

      
      <div class="control-group">
        <div class="ctrl-label">
          <span>Time (t)</span>
          <span class="ctrl-tag c-purple" id="valT">3 yrs</span>
        </div>
        <input type="range" id="rangeT" min="1" max="6" step="1" value="3">
      </div>
    </div>

    
    <div class="calc-box">
      <span class="math-pill c-blue" id="outI">$120</span>
      <span class="op">=</span>
      <span class="math-pill c-green" id="mathP">$1,000</span>
      <span class="op">×</span>
      <span class="math-pill c-amber" id="mathR">0.04</span>
      <span class="op">×</span>
      <span class="math-pill c-purple" id="mathT">3</span>
    </div>

    
    <div>
      <div class="growth-track">
        <div class="bar-p" id="barP" style="width: 70%;"></div>
        <div class="bar-i" id="barI" style="width: 30%;"></div>
      </div>
      <div class="bar-legend" style="margin-top: 4px;">
        <span style="color: #065f46;">● Principal: <span id="legP">$1,000</span></span>
        <span style="color: #1e3a8a;">● Interest: <span id="legI">+$120</span></span>
        <span style="color: #1e2945;">Total: <span id="legTotal">$1,120</span></span>
      </div>
    </div>
  </div>
</div>

<script>
  const rangeP = document.getElementById('rangeP');
  const rangeR = document.getElementById('rangeR');
  const rangeT = document.getElementById('rangeT');

  const valP = document.getElementById('valP');
  const valR = document.getElementById('valR');
  const valT = document.getElementById('valT');

  const outI = document.getElementById('outI');
  const mathP = document.getElementById('mathP');
  const mathR = document.getElementById('mathR');
  const mathT = document.getElementById('mathT');

  const barP = document.getElementById('barP');
  const barI = document.getElementById('barI');
  const legP = document.getElementById('legP');
  const legI = document.getElementById('legI');
  const legTotal = document.getElementById('legTotal');

  function update() {
    const p = parseFloat(rangeP.value);
    const rPct = parseFloat(rangeR.value);
    const rDec = rPct / 100;
    const t = parseFloat(rangeT.value);

    const interest = Math.round(p * rDec * t);
    const total = p + interest;

    // Update tags
    valP.textContent = `$${p.toLocaleString()}`;
    valR.textContent = `${rPct}% (${rDec.toFixed(2)})`;
    valT.textContent = `${t} yr${t > 1 ? 's' : ''}`;

    // Update Math formula line
    outI.textContent = `$${interest.toLocaleString()}`;
    mathP.textContent = `$${p.toLocaleString()}`;
    mathR.textContent = `${rDec.toFixed(2)}`;
    mathT.textContent = `${t}`;

    // Update bar ratio
    const pPercent = (p / total) * 100;
    const iPercent = (interest / total) * 100;
    barP.style.width = `${pPercent}%`;
    barI.style.width = `${iPercent}%`;

    // Legend
    legP.textContent = `$${p.toLocaleString()}`;
    legI.textContent = `+$${interest.toLocaleString()}`;
    legTotal.textContent = `$${total.toLocaleString()}`;
  }

  rangeP.addEventListener('input', update);
  rangeR.addEventListener('input', update);
  rangeT.addEventListener('input', update);

  update();
</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;
    }
    body {
      background: #ffffff;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }
    .diagram-content {
      width: 100%;
      max-width: 480px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }
    /* Formula Card */
    .formula-box {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px 14px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 15px;
      font-weight: 600;
    }
    .fraction {
      display: inline-flex;
      flex-direction: column;
      vertical-align: middle;
      text-align: center;
      padding: 0 4px;
    }
    .num {
      border-bottom: 1.5px solid #1e2945;
      padding-bottom: 2px;
      transition: color 0.3s ease;
    }
    .den {
      padding-top: 2px;
      transition: color 0.3s ease;
    }
    .mult {
      transition: color 0.3s ease;
    }
    /* Formula Highlights */
    .hl-1 .num { color: #10b981; }
    .hl-2 .fraction { color: #10b981; }
    .hl-2 .num { border-bottom-color: #10b981; }
    .hl-3 .mult { color: #10b981; }

    /* Steps Stack */
    .steps-list {
      display: flex;
      flex-direction: column;
      gap: 8px;
    }
    .step-card {
      background: #ffffff;
      border: 1px solid #e6e6e6;
      border-radius: 10px;
      padding: 10px 14px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      cursor: pointer;
      transition: all 0.3s ease;
      user-select: none;
    }
    .step-card:hover {
      background: #fafafa;
    }
    .step-card.active {
      border-color: #10b981;
      background: #ecfdf5;
      box-shadow: 0 0 0 1px #10b981;
    }
    .step-left {
      display: flex;
      align-items: center;
      gap: 10px;
    }
    .step-badge {
      width: 24px;
      height: 24px;
      border-radius: 50%;
      background: #e2e8f0;
      color: #64748b;
      font-size: 12px;
      font-weight: 700;
      display: flex;
      align-items: center;
      justify-content: center;
      transition: all 0.3s ease;
      flex-shrink: 0;
    }
    .step-card.active .step-badge {
      background: #10b981;
      color: #ffffff;
    }
    .step-title {
      font-size: 13px;
      font-weight: 600;
      color: #64748b;
      transition: color 0.3s ease;
    }
    .step-card.active .step-title {
      color: #065f46;
    }
    .step-math {
      font-size: 14px;
      font-weight: 600;
      color: #334155;
      letter-spacing: -0.2px;
    }
    .step-card.active .step-math {
      color: #047857;
      font-weight: 700;
    }

    /* Controls Bar */
    .controls {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 2px 4px;
    }
    .btn-play {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      color: #1e2945;
      border-radius: 8px;
      padding: 6px 12px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      transition: all 0.2s ease;
    }
    .btn-play:hover {
      border-color: #cbd5e1;
      background: #f8fafc;
    }
    .dots {
      display: flex;
      gap: 6px;
    }
    .dot {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      background: #e2e8f0;
      cursor: pointer;
      transition: all 0.2s ease;
      border: none;
      padding: 0;
    }
    .dot.active {
      background: #10b981;
      transform: scale(1.15);
    }

    @media (max-width: 380px) {
      .formula-box {
        font-size: 13px;
        padding: 10px;
      }
      .step-card {
        padding: 8px 10px;
      }
      .step-title {
        font-size: 12px;
      }
      .step-math {
        font-size: 13px;
      }
    }
  </style>
</head>
<body>
  <div class="diagram-content">
    
    <div id="formulaBox" class="formula-box hl-1">
      <span>Inflation Rate = [</span>
      <div class="fraction">
        <span class="num">CPI<sub>curr</sub> − CPI<sub>prev</sub></span>
        <span class="den">CPI<sub>prev</sub></span>
      </div>
      <span>]</span>
      <span class="mult">× 100%</span>
    </div>

    
    <div class="steps-list">
      <div class="step-card active" data-step="0">
        <div class="step-left">
          <div class="step-badge">1</div>
          <div class="step-title">Difference</div>
        </div>
        <div class="step-math">220.5 − 210 = 10.5</div>
      </div>

      <div class="step-card" data-step="1">
        <div class="step-left">
          <div class="step-badge">2</div>
          <div class="step-title">Relative Change</div>
        </div>
        <div class="step-math">10.5 ÷ 210 = 0.05</div>
      </div>

      <div class="step-card" data-step="2">
        <div class="step-left">
          <div class="step-badge">3</div>
          <div class="step-title">Percentage</div>
        </div>
        <div class="step-math">0.05 × 100 = 5.0%</div>
      </div>
    </div>

    
    <div class="controls">
      <button id="toggleBtn" class="btn-play">
        <span id="playIcon">⏸</span>
        <span id="playText">Pause</span>
      </button>

      <div class="dots">
        <button class="dot active" data-step="0" aria-label="Step 1"></button>
        <button class="dot" data-step="1" aria-label="Step 2"></button>
        <button class="dot" data-step="2" aria-label="Step 3"></button>
      </div>
    </div>
  </div>

  <script>
    const formulaBox = document.getElementById('formulaBox');
    const stepCards = Array.from(document.querySelectorAll('.step-card'));
    const dots = Array.from(document.querySelectorAll('.dot'));
    const toggleBtn = document.getElementById('toggleBtn');
    const playIcon = document.getElementById('playIcon');
    const playText = document.getElementById('playText');

    let currentStep = 0;
    let isPlaying = true;
    let timer = null;

    const hlClasses = ['hl-1', 'hl-2', 'hl-3'];

    function showStep(index) {
      currentStep = index;

      formulaBox.classList.remove('hl-1', 'hl-2', 'hl-3');
      formulaBox.classList.add(hlClasses[currentStep]);

      stepCards.forEach((card, i) => {
        card.classList.toggle('active', i === currentStep);
      });

      dots.forEach((dot, i) => {
        dot.classList.toggle('active', i === currentStep);
      });
    }

    function nextStep() {
      const next = (currentStep + 1) % stepCards.length;
      showStep(next);
    }

    function startAuto() {
      if (timer) clearInterval(timer);
      timer = setInterval(nextStep, 3500);
      isPlaying = true;
      playIcon.textContent = '⏸';
      playText.textContent = 'Pause';
    }

    function pauseAuto() {
      if (timer) clearInterval(timer);
      timer = null;
      isPlaying = false;
      playIcon.textContent = '▶';
      playText.textContent = 'Play';
    }

    toggleBtn.addEventListener('click', () => {
      if (isPlaying) {
        pauseAuto();
      } else {
        startAuto();
      }
    });

    stepCards.forEach((card, i) => {
      card.addEventListener('click', () => {
        showStep(i);
        pauseAuto();
      });
    });

    dots.forEach((dot, i) => {
      dot.addEventListener('click', () => {
        showStep(i);
        pauseAuto();
      });
    });

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

Consumer Price Index and Calculating Inflation Rates

<!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: #f8f9fa;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      width: 100%;
    }

    .grid-container {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 10px;
    }

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

    .basket-card {
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px;
      box-shadow: 0 2px 8px rgba(30, 41, 69, 0.05);
      display: flex;
      flex-direction: column;
      gap: 8px;
      transition: border-color 0.25s, box-shadow 0.25s;
      cursor: pointer;
    }

    .basket-card.active {
      border-color: #22b7ff;
      box-shadow: 0 4px 12px rgba(34, 183, 255, 0.18);
    }

    .basket-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
    }

    .basket-title {
      font-weight: 700;
      font-size: 15px;
    }

    .badge {
      font-size: 12px;
      font-weight: 700;
      padding: 3px 8px;
      border-radius: 20px;
      background: #f1f5f9;
      color: #1e2945;
    }

    .badge-primary {
      background: rgba(34, 183, 255, 0.15);
      color: #0284c7;
    }

    .item-list {
      display: flex;
      flex-direction: column;
      gap: 6px;
      font-size: 13px;
    }

    .item-row {
      display: flex;
      justify-content: space-between;
      align-items: center;
      padding: 4px 6px;
      background: #f8fafc;
      border-radius: 6px;
    }

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

    .total-row {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-weight: 700;
      font-size: 15px;
      padding-top: 6px;
      border-top: 1px dashed #cbd5e1;
    }

    .total-val {
      color: #0284c7;
    }

    .formula-card {
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px;
      box-shadow: 0 2px 8px rgba(30, 41, 69, 0.05);
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 10px;
    }

    .formula-flow {
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 15px;
      font-weight: 600;
    }

    .fraction {
      display: inline-flex;
      flex-direction: column;
      vertical-align: middle;
      text-align: center;
      padding: 0 4px;
    }

    .numerator {
      border-bottom: 2px solid #1e2945;
      padding-bottom: 2px;
    }

    .denominator {
      padding-top: 2px;
    }

    .hl-current {
      color: #0284c7;
      background: rgba(34, 183, 255, 0.12);
      padding: 1px 4px;
      border-radius: 4px;
      transition: background 0.2s;
    }

    .hl-base {
      color: #6366f1;
      background: rgba(99, 102, 241, 0.12);
      padding: 1px 4px;
      border-radius: 4px;
      transition: background 0.2s;
    }

    .cpi-result {
      font-size: 20px;
      font-weight: 800;
      color: #0284c7;
      padding: 2px 8px;
      border-radius: 6px;
      background: rgba(34, 183, 255, 0.15);
    }

    .controls {
      display: flex;
      justify-content: center;
      gap: 8px;
      width: 100%;
    }

    .step-btn {
      flex: 1;
      max-width: 160px;
      padding: 8px 12px;
      font-size: 13px;
      font-weight: 600;
      border: 1px solid #cbd5e1;
      border-radius: 8px;
      background: #ffffff;
      color: #1e2945;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 4px;
      transition: all 0.2s;
    }

    .step-btn.active {
      background: #22b7ff;
      border-color: #22b7ff;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(34, 183, 255, 0.3);
    }
  </style>
</head>
<body>

  <div class="grid-container">
    
    <div id="baseCard" class="basket-card" onclick="setStep(0)">
      <div class="basket-header">
        <span class="basket-title">Base Year Basket</span>
        <span class="badge">Base CPI = 100</span>
      </div>
      <div class="item-list">
        <div class="item-row">
          <span class="item-name">🛒 Groceries</span>
          <span>$80</span>
        </div>
        <div class="item-row">
          <span class="item-name">💻 Tech</span>
          <span>$70</span>
        </div>
        <div class="item-row">
          <span class="item-name">🎬 Entertainment</span>
          <span>$50</span>
        </div>
      </div>
      <div class="total-row">
        <span>Base Cost</span>
        <span class="total-val hl-base">$200</span>
      </div>
    </div>

    
    <div id="currCard" class="basket-card" onclick="setStep(1)">
      <div class="basket-header">
        <span class="basket-title">Current Year Basket</span>
        <span class="badge badge-primary">+25% Inflation</span>
      </div>
      <div class="item-list">
        <div class="item-row">
          <span class="item-name">🛒 Groceries</span>
          <span>$100</span>
        </div>
        <div class="item-row">
          <span class="item-name">💻 Tech</span>
          <span>$85</span>
        </div>
        <div class="item-row">
          <span class="item-name">🎬 Entertainment</span>
          <span>$65</span>
        </div>
      </div>
      <div class="total-row">
        <span>Current Cost</span>
        <span class="total-val hl-current">$250</span>
      </div>
    </div>
  </div>

  
  <div class="formula-card">
    <div class="formula-flow">
      <span>CPI =</span>
      <div class="fraction">
        <span class="numerator hl-current">Current Cost</span>
        <span class="denominator hl-base">Base Cost</span>
      </div>
      <span>× 100</span>
      <span>=</span>
      <div class="fraction">
        <span class="numerator hl-current">$250</span>
        <span class="denominator hl-base">$200</span>
      </div>
      <span>× 100</span>
      <span>=</span>
      <span class="cpi-result" id="resVal">125</span>
    </div>
  </div>

  
  <div class="controls">
    <button class="step-btn active" id="btn0" onclick="setStep(0)">1. Base ($200)</button>
    <button class="step-btn" id="btn1" onclick="setStep(1)">2. Current ($250)</button>
    <button class="step-btn" id="btn2" onclick="setStep(2)">3. Calculate CPI</button>
  </div>

  <script>
    let step = 0;
    const baseCard = document.getElementById('baseCard');
    const currCard = document.getElementById('currCard');
    const btn0 = document.getElementById('btn0');
    const btn1 = document.getElementById('btn1');
    const btn2 = document.getElementById('btn2');
    const resVal = document.getElementById('resVal');

    function setStep(s) {
      step = s;
      btn0.classList.toggle('active', s === 0);
      btn1.classList.toggle('active', s === 1);
      btn2.classList.toggle('active', s === 2);

      baseCard.classList.toggle('active', s === 0 || s === 2);
      currCard.classList.toggle('active', s === 1 || s === 2);

      if (s === 2) {
        resVal.style.transform = 'scale(1.1)';
        setTimeout(() => { resVal.style.transform = 'scale(1)'; }, 200);
      }
    }
  </script>
</body>
</html>

OGM.10.MPA.3

Aligned learning resources

Related diagrams