<!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;
      width: 100%;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      user-select: none;
    }

    /* Equation header */
    .header-box {
      width: 100%;
      max-width: 540px;
      text-align: center;
      background: #f0f7ff;
      border: 1px solid #bae0ff;
      border-radius: 10px;
      padding: 8px 12px;
      min-height: 48px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 17px;
      font-weight: 700;
      color: #1e2945;
    }

    .accent {
      color: #0284c7;
    }

    .highlight {
      background: #e0f2fe;
      padding: 2px 6px;
      border-radius: 4px;
      border: 1px dashed #0284c7;
    }

    /* Place value block columns */
    .stage {
      width: 100%;
      max-width: 540px;
      display: grid;
      grid-template-columns: 1.3fr 1.3fr 0.8fr;
      gap: 8px;
      margin: 10px 0;
    }

    .column {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 8px 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      min-height: 210px;
      position: relative;
    }

    .col-title {
      font-size: 13px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #64748b;
      margin-bottom: 8px;
    }

    .blocks-container {
      width: 100%;
      height: 100%;
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      justify-content: center;
      gap: 4px;
      align-content: center;
    }

    /* Base ten SVG block styles */
    .flat {
      width: 44px;
      height: 44px;
      transition: all 0.3s ease;
    }

    .flat-new {
      box-shadow: 0 0 0 2px #0284c7, 0 0 10px rgba(34, 183, 255, 0.5);
      border-radius: 2px;
    }

    .rod {
      width: 7px;
      height: 44px;
      transition: all 0.3s ease;
    }

    .rod-incoming {
      animation: pulse 1.2s infinite ease-in-out;
      filter: drop-shadow(0 0 4px #0284c7);
    }

    .unit {
      width: 8px;
      height: 8px;
    }

    .units-grid {
      display: grid;
      grid-template-columns: repeat(2, 8px);
      gap: 4px;
      justify-content: center;
    }

    /* Regrouping box overlay */
    .grouping-zone {
      position: absolute;
      inset: 32px 4px 34px 4px;
      border: 2px dashed #0284c7;
      background: rgba(34, 183, 255, 0.08);
      border-radius: 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-end;
      padding-bottom: 4px;
      pointer-events: none;
      box-shadow: 0 0 8px rgba(34, 183, 255, 0.3);
    }

    .group-tag {
      background: #0284c7;
      color: #fff;
      font-size: 11px;
      font-weight: 700;
      padding: 2px 6px;
      border-radius: 4px;
      white-space: nowrap;
    }

    .count-badge {
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
      margin-top: auto;
      padding-top: 6px;
    }

    /* Controls bar */
    .controls {
      width: 100%;
      max-width: 540px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
      padding-top: 4px;
    }

    .btn-group {
      display: flex;
      gap: 6px;
    }

    button {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      font-size: 13px;
      font-weight: 600;
      padding: 6px 12px;
      border-radius: 6px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 4px;
      min-height: 32px;
      touch-action: manipulation;
    }

    button:active {
      background: #e2e8f0;
    }

    .btn-primary {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
    }

    .btn-primary:active {
      background: #0369a1;
    }

    .dots {
      display: flex;
      gap: 6px;
    }

    .dot {
      width: 9px;
      height: 9px;
      border-radius: 50%;
      background: #cbd5e1;
      cursor: pointer;
      transition: background 0.2s ease, transform 0.2s ease;
    }

    .dot.active {
      background: #0284c7;
      transform: scale(1.2);
    }

    @keyframes pulse {
      0%, 100% { transform: scale(1); opacity: 1; }
      50% { transform: scale(1.08); opacity: 0.85; }
    }

    @media (max-width: 400px) {
      .flat { width: 36px; height: 36px; }
      .rod { width: 6px; height: 36px; }
      .header-box { font-size: 15px; }
      .column { min-height: 195px; }
    }
  </style>
</head>
<body>

  
  <div class="header-box" id="stepText">
    496 = 4 hundreds + 9 tens + 6 ones
  </div>

  
  <div class="stage">
    
    <div class="column">
      <div class="col-title">Hundreds</div>
      <div class="blocks-container" id="hundredsContainer"></div>
      <div class="count-badge" id="hundredsCount">400</div>
    </div>

    
    <div class="column" id="tensCol">
      <div class="col-title">Tens</div>
      <div class="blocks-container" id="tensContainer"></div>
      <div class="grouping-zone" id="regroupBox" style="display: none;">
        <span class="group-tag">10 tens → 1 hundred</span>
      </div>
      <div class="count-badge" id="tensCount">90</div>
    </div>

    
    <div class="column">
      <div class="col-title">Ones</div>
      <div class="blocks-container">
        <div class="units-grid" id="onesGrid"></div>
      </div>
      <div class="count-badge">6</div>
    </div>
  </div>

  
  <div class="controls">
    <button id="prevBtn" onclick="prevStep()">← Prev</button>
    <div class="dots">
      <div class="dot active" onclick="goToStep(0)"></div>
      <div class="dot" onclick="goToStep(1)"></div>
      <div class="dot" onclick="goToStep(2)"></div>
      <div class="dot" onclick="goToStep(3)"></div>
    </div>
    <div class="btn-group">
      <button id="playBtn" onclick="togglePlay()">⏸</button>
      <button class="btn-primary" id="nextBtn" onclick="nextStep()">Next →</button>
    </div>
  </div>

  <script>
    // SVG Templates
    const flatSVG = (isNew = false) => `
      <svg class="flat ${isNew ? 'flat-new' : ''}" viewBox="0 0 100 100">
        <rect x="2" y="2" width="96" height="96" rx="3" fill="#e0f2fe" stroke="#0284c7" stroke-width="3"/>
        <path d="M10,0 v100 M20,0 v100 M30,0 v100 M40,0 v100 M50,0 v100 M60,0 v100 M70,0 v100 M80,0 v100 M90,0 v100" stroke="#0284c7" stroke-width="0.8" opacity="0.6"/>
        <path d="M0,10 h100 M0,20 h100 M0,30 h100 M0,40 h100 M0,50 h100 M0,60 h100 M0,70 h100 M0,80 h100 M0,90 h100" stroke="#0284c7" stroke-width="0.8" opacity="0.6"/>
      </svg>`;

    const rodSVG = (incoming = false) => `
      <svg class="rod ${incoming ? 'rod-incoming' : ''}" viewBox="0 0 14 100">
        <rect x="1" y="1" width="12" height="98" rx="2" fill="${incoming ? '#38bdf8' : '#e0f2fe'}" stroke="${incoming ? '#0369a1' : '#0284c7'}" stroke-width="2"/>
        <path d="M0,10 h14 M0,20 h14 M0,30 h14 M0,40 h14 M0,50 h14 M0,60 h14 M0,70 h14 M0,80 h14 M0,90 h14" stroke="${incoming ? '#0369a1' : '#0284c7'}" stroke-width="1.2" opacity="0.8"/>
      </svg>`;

    const unitSVG = () => `
      <svg class="unit" viewBox="0 0 10 10">
        <rect x="1" y="1" width="8" height="8" rx="1" fill="#e0f2fe" stroke="#0284c7" stroke-width="1.5"/>
      </svg>`;

    // Build constant ones grid
    const onesGrid = document.getElementById('onesGrid');
    onesGrid.innerHTML = Array(6).fill(unitSVG()).join('');

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

    const steps = [
      {
        text: 'Start with <b>496</b> &nbsp;(49 tens, 6 ones)',
        flats: 4,
        rods: 9,
        hasIncoming: false,
        regroup: false,
        hundredsVal: '400',
        tensVal: '90'
      },
      {
        text: 'Add 1 ten: &nbsp;<b>49 tens + 1 ten = 50 tens</b>',
        flats: 4,
        rods: 10,
        hasIncoming: true,
        regroup: false,
        hundredsVal: '400',
        tensVal: '+10'
      },
      {
        text: '<span class="highlight">10 tens regroup into 1 hundred</span>',
        flats: 4,
        rods: 10,
        hasIncoming: false,
        regroup: true,
        hundredsVal: '400',
        tensVal: '10 tens'
      },
      {
        text: '<b>496 + 10 = 506</b> &nbsp;(5 hundreds, 6 ones)',
        flats: 5,
        newFlat: true,
        rods: 0,
        hasIncoming: false,
        regroup: false,
        hundredsVal: '500',
        tensVal: '0'
      }
    ];

    function render() {
      const s = steps[currentStep];

      // Update text
      document.getElementById('stepText').innerHTML = s.text;

      // Update Hundreds
      const hContainer = document.getElementById('hundredsContainer');
      let flatsHTML = '';
      for (let i = 0; i < s.flats; i++) {
        const isNew = (s.newFlat && i === s.flats - 1);
        flatsHTML += flatSVG(isNew);
      }
      hContainer.innerHTML = flatsHTML;
      document.getElementById('hundredsCount').textContent = s.hundredsVal;

      // Update Tens
      const tContainer = document.getElementById('tensContainer');
      let rodsHTML = '';
      for (let i = 0; i < s.rods; i++) {
        const incoming = (s.hasIncoming && i === s.rods - 1);
        rodsHTML += rodSVG(incoming);
      }
      tContainer.innerHTML = rodsHTML;
      document.getElementById('tensCount').textContent = s.tensVal;

      // Regroup box
      document.getElementById('regroupBox').style.display = s.regroup ? 'flex' : 'none';

      // Update Dots
      document.querySelectorAll('.dot').forEach((dot, idx) => {
        dot.classList.toggle('active', idx === currentStep);
      });
    }

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

    function nextStep() {
      currentStep = (currentStep + 1) % steps.length;
      render();
    }

    function prevStep() {
      currentStep = (currentStep - 1 + steps.length) % steps.length;
      render();
    }

    function togglePlay() {
      playing = !playing;
      document.getElementById('playBtn').textContent = playing ? '⏸' : '▶';
      if (playing) startAutoPlay();
      else clearInterval(timer);
    }

    function startAutoPlay() {
      clearInterval(timer);
      timer = setInterval(() => {
        if (playing) nextStep();
      }, 3500);
    }

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

Finding 10 More and 10 Less Than a Three-Digit Number

<!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>Mental Math: Total Tens</title>
  <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: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
    }

    /* Top: Number Badge Split */
    .split-badge {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      margin-bottom: 6px;
    }
    .badge {
      display: inline-flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 4px 10px;
      border-radius: 8px;
      font-weight: 700;
      line-height: 1.1;
      transition: all 0.3s ease;
    }
    .badge-tens {
      background: #eff6ff;
      border: 1.5px solid #3b82f6;
      color: #1d4ed8;
    }
    .badge-ones {
      background: #f0fdf4;
      border: 1.5px solid #22c55e;
      color: #15803d;
    }
    .badge .val {
      font-size: 20px;
    }
    .badge .lbl {
      font-size: 11px;
      font-weight: 600;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }
    .badge-op {
      font-size: 18px;
      font-weight: 700;
      color: #64748b;
    }

    /* Model Visual Stage */
    .stage {
      width: 100%;
      max-width: 480px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 8px;
      position: relative;
      min-height: 190px;
      justify-content: center;
    }

    .models-container {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 14px;
      width: 100%;
      flex-wrap: wrap;
    }

    /* Base-Ten Visuals */
    .group-block {
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 4px;
    }
    .flats-grid {
      display: grid;
      grid-template-columns: repeat(3, 38px);
      gap: 5px;
    }
    .flat {
      width: 38px;
      height: 38px;
      background: #dbeafe;
      border: 1.5px solid #3b82f6;
      border-radius: 3px;
      background-image: 
        linear-gradient(to right, rgba(59, 130, 246, 0.25) 1px, transparent 1px),
        linear-gradient(to bottom, rgba(59, 130, 246, 0.25) 1px, transparent 1px);
      background-size: 3.8px 3.8px;
      transition: all 0.4s ease;
    }
    .flat.unbundled {
      opacity: 0.2;
      border-style: dashed;
      transform: scale(0.9);
    }

    /* Rods (10s) */
    .rods-group {
      display: flex;
      gap: 3px;
      align-items: flex-end;
      height: 40px;
      padding: 0 4px;
      border-left: 2px dashed #cbd5e1;
      min-width: 60px;
      justify-content: center;
    }
    .rod {
      width: 5px;
      height: 38px;
      background: #60a5fa;
      border: 1px solid #2563eb;
      border-radius: 1.5px;
      transition: all 0.3s ease;
    }
    .rod.removed {
      opacity: 0.15;
      background: #ef4444;
      border-color: #dc2626;
      transform: translateY(6px);
      text-decoration: line-through;
    }

    /* Units (1s) */
    .ones-group {
      display: flex;
      flex-wrap: wrap;
      width: 28px;
      gap: 3px;
      align-items: center;
      padding-left: 8px;
      border-left: 2px solid #e2e8f0;
    }
    .unit {
      width: 7px;
      height: 7px;
      background: #86efac;
      border: 1px solid #16a34a;
      border-radius: 1px;
    }

    /* Equation Bar */
    .equation-bar {
      margin-top: 4px;
      padding: 6px 14px;
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      font-size: 15px;
      font-weight: 700;
      display: flex;
      align-items: center;
      gap: 6px;
      color: #334155;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }
    .eq-blue { color: #2563eb; }
    .eq-red { color: #dc2626; }
    .eq-green { color: #16a34a; }

    /* Stepper Controls */
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      width: 100%;
      margin-top: 8px;
    }
    .btn-step {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      color: #475569;
      font-size: 12px;
      font-weight: 600;
      padding: 5px 10px;
      border-radius: 6px;
      cursor: pointer;
      transition: background 0.2s;
    }
    .btn-step.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
    }
    .btn-nav {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      width: 30px;
      height: 30px;
      border-radius: 6px;
      display: flex;
      align-items: center;
      justify-content: center;
      cursor: pointer;
      font-weight: bold;
    }
  </style>
</head>
<body>

  
  <div class="split-badge">
    <div class="badge badge-tens" id="badgeTens">
      <span class="val" id="tensVal">60 tens</span>
      <span class="lbl">600</span>
    </div>
    <span class="badge-op">+</span>
    <div class="badge badge-ones">
      <span class="val">7 ones</span>
      <span class="lbl">7</span>
    </div>
    <span class="badge-op">=</span>
    <div class="badge" style="background:#f8fafc; border:1.5px solid #94a3b8; color:#1e2945;">
      <span class="val" id="totalVal">607</span>
      <span class="lbl">Total</span>
    </div>
  </div>

  
  <div class="stage">
    <div class="models-container">
      
      <div class="group-block">
        <div class="flats-grid" id="flatsGrid">
          <div class="flat"></div>
          <div class="flat"></div>
          <div class="flat"></div>
          <div class="flat"></div>
          <div class="flat"></div>
          <div class="flat" id="unbundledFlat"></div>
        </div>
      </div>

      
      <div class="rods-group" id="rodsContainer">
        
      </div>

      
      <div class="ones-group" title="7 Ones (unchanged)">
        <div class="unit"></div><div class="unit"></div>
        <div class="unit"></div><div class="unit"></div>
        <div class="unit"></div><div class="unit"></div>
        <div class="unit"></div>
      </div>
    </div>

    
    <div class="equation-bar" id="eqBar">
      <span class="eq-blue">60 tens</span>
      <span>−</span>
      <span class="eq-red">1 ten</span>
      <span>=</span>
      <span class="eq-blue">59 tens</span>
      <span>(597)</span>
    </div>
  </div>

  
  <div class="controls">
    <button class="btn-nav" id="prevBtn" aria-label="Previous">◀</button>
    <button class="btn-step active" data-step="0">1. Total Tens</button>
    <button class="btn-step" data-step="1">2. Unbundle</button>
    <button class="btn-step" data-step="2">3. Subtract 10</button>
    <button class="btn-step" data-step="3">4. Result (597)</button>
    <button class="btn-nav" id="nextBtn" aria-label="Next">▶</button>
  </div>

  <script src="{{VENDOR_CDN}}/classace-diagram.js"></script>
  <script>
    const rodsContainer = document.getElementById('rodsContainer');
    const unbundledFlat = document.getElementById('unbundledFlat');
    const eqBar = document.getElementById('eqBar');
    const tensVal = document.getElementById('tensVal');
    const totalVal = document.getElementById('totalVal');
    const stepBtns = document.querySelectorAll('.btn-step');

    // Build 10 rods
    for (let i = 0; i < 10; i++) {
      const r = document.createElement('div');
      r.className = 'rod';
      r.id = 'rod-' + i;
      rodsContainer.appendChild(r);
    }

    const steps = [
      {
        flatsUnbundled: false,
        showRods: false,
        rodRemoved: false,
        eq: '<span class="eq-blue">60 tens</span> + <span class="eq-green">7 ones</span> = 607',
        tensText: '60 tens',
        totalText: '607'
      },
      {
        flatsUnbundled: true,
        showRods: true,
        rodRemoved: false,
        eq: '<span class="eq-blue">5 flats + 10 rods</span> = 60 tens',
        tensText: '60 tens',
        totalText: '607'
      },
      {
        flatsUnbundled: true,
        showRods: true,
        rodRemoved: true,
        eq: '<span class="eq-blue">60 tens</span> − <span class="eq-red">1 ten</span> = <span class="eq-blue">59 tens</span>',
        tensText: '59 tens',
        totalText: '597'
      },
      {
        flatsUnbundled: true,
        showRods: true,
        rodRemoved: true,
        eq: '<span class="eq-blue">590</span> + <span class="eq-green">7</span> = <strong>597</strong>',
        tensText: '59 tens',
        totalText: '597'
      }
    ];

    let currentStep = 0;

    function renderStep(idx) {
      currentStep = idx;
      const s = steps[idx];

      // Update buttons
      stepBtns.forEach((b, i) => b.classList.toggle('active', i === idx));

      // Update Flat
      unbundledFlat.classList.toggle('unbundled', s.flatsUnbundled);

      // Update Rods
      rodsContainer.style.display = s.showRods ? 'flex' : 'none';
      const lastRod = document.getElementById('rod-9');
      if (lastRod) {
        lastRod.classList.toggle('removed', s.rodRemoved);
      }

      // Equation & Badges
      eqBar.innerHTML = s.eq;
      tensVal.textContent = s.tensText;
      totalVal.textContent = s.totalText;
    }

    stepBtns.forEach((btn, i) => {
      btn.addEventListener('click', () => renderStep(i));
    });

    document.getElementById('prevBtn').addEventListener('click', () => {
      renderStep((currentStep - 1 + steps.length) % steps.length);
    });

    document.getElementById('nextBtn').addEventListener('click', () => {
      renderStep((currentStep + 1) % steps.length);
    });

    renderStep(0);
  </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: transparent;
      color: #1e2945;
      padding: 8px;
      display: flex;
      flex-direction: column;
      gap: 8px;
      width: 100%;
      min-height: 100%;
      justify-content: center;
    }

    /* Transition Connectors Bar */
    .nav-arrows {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      padding: 0 4px;
    }

    .arrow-badge {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      padding: 5px 8px;
      border-radius: 20px;
      font-size: 11px;
      font-weight: 700;
      letter-spacing: -0.2px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.05);
    }

    .arrow-left {
      background: #fef3c7;
      color: #92400e;
      border: 1px dashed #f59e0b;
    }

    .arrow-right {
      background: #dcfce7;
      color: #166534;
      border: 1px dashed #22c55e;
    }

    /* Main 3 Columns */
    .columns-grid {
      display: grid;
      grid-template-columns: 1fr 1.08fr 1fr;
      gap: 6px;
      align-items: stretch;
    }

    .column-card {
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 12px;
      padding: 8px 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 6px;
      position: relative;
    }

    .column-card.center-start {
      background: #f0f9ff;
      border-color: #38bdf8;
      box-shadow: 0 4px 12px rgba(2, 132, 199, 0.08);
      z-index: 1;
    }

    /* Top Badges */
    .col-badge {
      font-size: 10px;
      font-weight: 700;
      padding: 2px 8px;
      border-radius: 12px;
      text-transform: uppercase;
      letter-spacing: 0.3px;
      white-space: nowrap;
    }

    .badge-less { background: #fde68a; color: #78350f; }
    .badge-start { background: #0284c7; color: #ffffff; }
    .badge-more { background: #bbf7d0; color: #14532d; }

    /* Large Numbers */
    .number-display {
      font-size: 26px;
      font-weight: 800;
      letter-spacing: 1px;
      display: flex;
      align-items: baseline;
      gap: 1px;
      line-height: 1;
      margin: 2px 0;
    }

    .digit-h, .digit-o {
      color: #64748b;
    }

    .digit-t-less {
      color: #d97706;
      background: #fef3c7;
      padding: 0 3px;
      border-radius: 4px;
    }

    .digit-t-start {
      color: #0284c7;
      background: #e0f2fe;
      padding: 0 4px;
      border-radius: 5px;
      outline: 1.5px solid #38bdf8;
    }

    .digit-t-more {
      color: #16a34a;
      background: #dcfce7;
      padding: 0 3px;
      border-radius: 4px;
    }

    /* Place Value Sub-label */
    .place-labels {
      display: flex;
      justify-content: space-around;
      width: 100%;
      font-size: 9px;
      font-weight: 700;
      color: #94a3b8;
      border-bottom: 1px solid #f1f5f9;
      padding-bottom: 3px;
    }

    .place-labels span.active-h { color: #64748b; }
    .place-labels span.active-t { color: #0284c7; }
    .place-labels span.active-o { color: #64748b; }

    /* Partitioned H | T | O Visual Area */
    .pto-grid {
      display: grid;
      grid-template-columns: 1fr 1fr 0.6fr;
      width: 100%;
      gap: 3px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 3px;
      min-height: 88px;
      align-items: center;
    }

    .pto-cell {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 3px;
      height: 100%;
    }

    .pto-cell.tens-cell {
      background: #ffffff;
      border-radius: 5px;
      padding: 2px;
      border: 1px dashed #cbd5e1;
    }

    .pto-cell.tens-cell.active-center {
      border-color: #38bdf8;
      background: #f0f9ff;
    }

    .pto-cell.tens-cell.active-less {
      border-color: #fbbf24;
      background: #fffbeb;
    }

    .pto-cell.tens-cell.active-more {
      border-color: #4ade80;
      background: #f0fdf4;
    }

    /* Base-10 SVGs */
    .svg-flat {
      width: 22px;
      height: 22px;
      filter: drop-shadow(0 1px 1px rgba(0,0,0,0.06));
    }

    .svg-rod {
      width: 5px;
      height: 25px;
    }

    .svg-unit {
      width: 6px;
      height: 6px;
    }

    .rods-wrap {
      display: flex;
      gap: 2px;
      align-items: center;
      justify-content: center;
      flex-wrap: wrap;
    }

    .units-wrap {
      display: flex;
      flex-direction: column;
      gap: 3px;
      align-items: center;
      justify-content: center;
    }

    .flats-wrap {
      display: flex;
      flex-direction: column;
      gap: 2px;
      align-items: center;
    }

    /* Bottom Summary Callout */
    .takeaway-banner {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 10px;
      padding: 7px 12px;
      display: flex;
      align-items: center;
      justify-content: space-around;
      font-size: 11.5px;
      color: #334155;
      box-shadow: 0 1px 2px rgba(0,0,0,0.04);
    }

    .pill-tag {
      font-weight: 700;
      padding: 2px 7px;
      border-radius: 6px;
      font-size: 11px;
    }

    .pill-gray { background: #f1f5f9; color: #475569; border: 1px solid #cbd5e1; }
    .pill-blue { background: #e0f2fe; color: #0369a1; border: 1px solid #bae6fd; }

    @media (max-width: 400px) {
      .number-display { font-size: 21px; }
      .svg-flat { width: 18px; height: 18px; }
      .svg-rod { width: 4px; height: 21px; }
      .svg-unit { width: 5px; height: 5px; }
      .col-badge { font-size: 9px; padding: 2px 5px; }
      .takeaway-banner { font-size: 10px; flex-direction: column; gap: 4px; text-align: center; }
      .arrow-badge { font-size: 10px; }
    }
  </style>
</head>
<body>

  
  <div class="nav-arrows">
    <div class="arrow-badge arrow-left">
      <span>← −10</span>
      <span>(4 tens → 3 tens)</span>
    </div>
    <div class="arrow-badge arrow-right">
      <span>+10 →</span>
      <span>(4 tens → 5 tens)</span>
    </div>
  </div>

  
  <div class="columns-grid">

    
    <div class="column-card">
      <span class="col-badge badge-less">−10 Less</span>
      <div class="number-display">
        <span class="digit-h">3</span>
        <span class="digit-t-less">3</span>
        <span class="digit-o">2</span>
      </div>
      
      <div class="place-labels">
        <span>300</span>
        <span style="color:#d97706;">30</span>
        <span>2</span>
      </div>

      <div class="pto-grid">
        
        <div class="pto-cell flats-wrap">
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
        </div>

        
        <div class="pto-cell tens-cell active-less">
          <div class="rods-wrap">
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#fde68a" stroke="#d97706" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#d97706" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#fde68a" stroke="#d97706" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#d97706" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#fde68a" stroke="#d97706" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#d97706" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#d97706" stroke-width="0.3"/>
            </svg>
          </div>
        </div>

        
        <div class="pto-cell units-wrap">
          <svg class="svg-unit" viewBox="0 0 4 4">
            <rect width="4" height="4" fill="#a7f3d0" stroke="#059669" stroke-width="0.8"/>
          </svg>
          <svg class="svg-unit" viewBox="0 0 4 4">
            <rect width="4" height="4" fill="#a7f3d0" stroke="#059669" stroke-width="0.8"/>
          </svg>
        </div>
      </div>
    </div>

    
    <div class="column-card center-start">
      <span class="col-badge badge-start">Start Number</span>
      <div class="number-display">
        <span class="digit-h">3</span>
        <span class="digit-t-start">4</span>
        <span class="digit-o">2</span>
      </div>

      <div class="place-labels">
        <span class="active-h">300</span>
        <span class="active-t">40</span>
        <span class="active-o">2</span>
      </div>

      <div class="pto-grid">
        
        <div class="pto-cell flats-wrap">
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
        </div>

        
        <div class="pto-cell tens-cell active-center">
          <div class="rods-wrap">
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bae6fd" stroke="#0284c7" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#0284c7" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bae6fd" stroke="#0284c7" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#0284c7" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bae6fd" stroke="#0284c7" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#0284c7" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bae6fd" stroke="#0284c7" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#0284c7" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#0284c7" stroke-width="0.3"/>
            </svg>
          </div>
        </div>

        
        <div class="pto-cell units-wrap">
          <svg class="svg-unit" viewBox="0 0 4 4">
            <rect width="4" height="4" fill="#a7f3d0" stroke="#059669" stroke-width="0.8"/>
          </svg>
          <svg class="svg-unit" viewBox="0 0 4 4">
            <rect width="4" height="4" fill="#a7f3d0" stroke="#059669" stroke-width="0.8"/>
          </svg>
        </div>
      </div>
    </div>

    
    <div class="column-card">
      <span class="col-badge badge-more">+10 More</span>
      <div class="number-display">
        <span class="digit-h">3</span>
        <span class="digit-t-more">5</span>
        <span class="digit-o">2</span>
      </div>

      <div class="place-labels">
        <span>300</span>
        <span style="color:#16a34a;">50</span>
        <span>2</span>
      </div>

      <div class="pto-grid">
        
        <div class="pto-cell flats-wrap">
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
          <svg class="svg-flat" viewBox="0 0 10 10">
            <rect width="10" height="10" fill="#a7f3d0" stroke="#059669" stroke-width="0.8" />
            <path d="M1,0 V10 M2,0 V10 M3,0 V10 M4,0 V10 M5,0 V10 M6,0 V10 M7,0 V10 M8,0 V10 M9,0 V10 M0,1 H10 M0,2 H10 M0,3 H10 M0,4 H10 M0,5 H10 M0,6 H10 M0,7 H10 M0,8 H10 M0,9 H10" stroke="#059669" stroke-width="0.25" opacity="0.6"/>
          </svg>
        </div>

        
        <div class="pto-cell tens-cell active-more">
          <div class="rods-wrap">
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bbf7d0" stroke="#16a34a" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#16a34a" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bbf7d0" stroke="#16a34a" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#16a34a" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bbf7d0" stroke="#16a34a" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#16a34a" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bbf7d0" stroke="#16a34a" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#16a34a" stroke-width="0.3"/>
            </svg>
            <svg class="svg-rod" viewBox="0 0 2 10">
              <rect width="2" height="10" fill="#bbf7d0" stroke="#16a34a" stroke-width="0.5"/>
              <line x1="0" y1="2" x2="2" y2="2" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="4" x2="2" y2="4" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="6" x2="2" y2="6" stroke="#16a34a" stroke-width="0.3"/>
              <line x1="0" y1="8" x2="2" y2="8" stroke="#16a34a" stroke-width="0.3"/>
            </svg>
          </div>
        </div>

        
        <div class="pto-cell units-wrap">
          <svg class="svg-unit" viewBox="0 0 4 4">
            <rect width="4" height="4" fill="#a7f3d0" stroke="#059669" stroke-width="0.8"/>
          </svg>
          <svg class="svg-unit" viewBox="0 0 4 4">
            <rect width="4" height="4" fill="#a7f3d0" stroke="#059669" stroke-width="0.8"/>
          </svg>
        </div>
      </div>
    </div>

  </div>

  
  <div class="takeaway-banner">
    <div>
      Hundreds &amp; Ones stay unchanged: <span class="pill-tag pill-gray">3 _ 2</span>
    </div>
    <div>
      Only Tens change: <span class="pill-tag pill-blue">3 ➔ 4 ➔ 5</span>
    </div>
  </div>

</body>
</html>

OGM.4.NBT.2

Aligned learning resources

Related diagrams