* { margin: 0; padding: 0; box-sizing: border-box; }
        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
            background: linear-gradient(135deg, #10b981 0%, #059669 100%);
            min-height: 100vh;
            color: #333;
            padding: 20px;
        }
        .container { max-width: 1200px; margin: 0 auto; }
        header {
            background: rgba(255, 255, 255, 0.98);
            border-radius: 16px;
            padding: 20px 30px;
            margin-bottom: 20px;
            box-shadow: 0 10px 40px rgba(0,0,0,0.2);
        }
        h1 {
            font-size: 28px;
            background: linear-gradient(135deg, #10b981, #059669);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            margin-bottom: 10px;
        }
        .subtitle { color: #666; font-size: 14px; }
        .main-content {
            background: rgba(255, 255, 255, 0.98);
            border-radius: 16px;
            padding: 30px;
            box-shadow: 0 10px 40px rgba(0,0,0,0.2);
        }
        .pedagogy-badge {
            display: inline-block;
            padding: 8px 16px;
            background: linear-gradient(135deg, #10b981, #059669);
            color: white;
            border-radius: 20px;
            font-size: 12px;
            font-weight: 600;
            text-transform: uppercase;
            margin-bottom: 20px;
        }
        .description {
            background: linear-gradient(135deg, #10b98115, #05966915);
            padding: 20px;
            border-radius: 12px;
            margin-bottom: 25px;
            border-left: 4px solid #10b981;
        }
        .comparison-container {
            margin: 25px 0;
            padding: 20px;
            background: #f8fafc;
            border-radius: 12px;
        }
        .method-header {
            padding: 12px 20px;
            border-radius: 8px;
            font-weight: 600;
            margin-bottom: 15px;
            font-size: 16px;
            color: white;
        }
        .blocked-header {
            background: linear-gradient(135deg, #dc2626, #991b1b);
        }
        .interleaved-header {
            background: linear-gradient(135deg, #10b981, #059669);
        }
        .problem-sequence {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
            gap: 10px;
            margin: 15px 0;
        }
        .problem-card {
            padding: 15px 10px;
            border-radius: 8px;
            text-align: center;
            font-weight: 600;
            font-size: 13px;
            border: 2px solid;
        }
        .cube { background: linear-gradient(135deg, #6a11cb10, #2575fc10); border-color: #6a11cb; color: #6a11cb; }
        .cylinder { background: linear-gradient(135deg, #f5961410, #fbbf2410); border-color: #f59e0b; color: #f59e0b; }
        .sphere { background: linear-gradient(135deg, #dc262610, #99 1b1b10); border-color: #dc2626; color: #dc2626; }
        .insight-box {
            background: linear-gradient(135deg, #10b98110, #05966910);
            padding: 15px;
            border-radius: 8px;
            border-left: 3px solid #10b981;
            margin: 15px 0;
        }
        .warning-box {
            background: linear-gradient(135deg, #dc262610, #991b1b10);
            padding: 15px;
            border-radius: 8px;
            border-left: 3px solid #dc2626;
            margin: 15px 0;
        }
        .benefits-section {
            background: linear-gradient(135deg, #10b98110, #05966910);
            padding: 20px;
            border-radius: 12px;
            border-left: 4px solid #10b981;
            margin-top: 25px;
        }
        .benefits-section h3 {
            color: #10b981;
            margin-bottom: 15px;
            font-size: 16px;
        }
        .benefits-section ul {
            list-style: none;
            padding: 0;
        }
        .benefits-section li {
            padding: 8px 0;
            color: #444;
            font-size: 14px;
            line-height: 1.6;
        }
        .benefits-section li::before {
            content: "✓";
            color: #10b981;
            font-weight: bold;
            margin-right: 10px;
        }
        .action-bar {
            display: flex;
            gap: 15px;
            justify-content: center;
            padding: 20px 0;
            border-top: 1px solid #e0e0e0;
            margin-top: 20px;
        }
        .action-btn {
            padding: 12px 30px;
            border: none;
            border-radius: 10px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            font-size: 14px;
        }
        .nav-btn {
            background: white;
            color: #10b981;
            border: 2px solid #10b981;
        }
        .nav-btn:hover {
            background: #10b981;
            color: white;
            transform: translateY(-2px);
        }
        .formula-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 15px;
            margin: 20px 0;
        }
        .formula-card {
            background: white;
            padding: 15px;
            border-radius: 8px;
            text-align: center;
        }