* { margin: 0; padding: 0; box-sizing: border-box; }
        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 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, #667eea, #764ba2);
            -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, #667eea, #764ba2);
            color: white;
            border-radius: 20px;
            font-size: 12px;
            font-weight: 600;
            text-transform: uppercase;
            margin-bottom: 20px;
        }
        .description {
            background: linear-gradient(135deg, #667eea15, #764ba215);
            padding: 20px;
            border-radius: 12px;
            margin-bottom: 25px;
            border-left: 4px solid #667eea;
        }
        .problem-box {
            background: white;
            padding: 20px;
            border-radius: 10px;
            margin: 20px 0;
            border: 2px solid #667eea;
            font-size: 24px;
            text-align: center;
        }
        .step-container {
            margin-bottom: 20px;
        }
        .step-box {
            background: #f8fafc;
            padding: 15px;
            border-radius: 8px;
            margin: 10px 0;
            border-left: 4px solid #667eea;
        }
        .step-correct {
            background: linear-gradient(135deg, #10b98110, #05966910);
            border-left-color: #10b981;
        }
        .step-error {
            background: linear-gradient(135deg, #dc262620, #dc262610);
            border-left-color: #dc2626;
        }
        .student-work {
            font-size: 18px;
            font-weight: 600;
            margin-bottom: 10px;
            color: #2c3e50;
        }
        .ai-intervention {
            background: linear-gradient(135deg, #f5961410, #fbbf2410);
            padding: 12px;
            border-radius: 8px;
            margin: 10px 0;
            border-left: 3px solid #f59e0b;
            font-size: 14px;
        }
        .cognitive-model {
            background: white;
            padding: 20px;
            border-radius: 10px;
            margin: 20px 0;
            border: 2px solid #764ba2;
        }
        .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: #667eea;
            border: 2px solid #667eea;
        }
        .nav-btn:hover {
            background: #667eea;
            color: white;
            transform: translateY(-2px);
        }