* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            padding: 20px;
            line-height: 1.6;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            background: white;
            border-radius: 25px;
            padding: 40px;
            box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
        }

        h1 {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
            font-size: 2.8em;
            margin-bottom: 10px;
            text-align: center;
            font-weight: 700;
        }

        .subtitle {
            text-align: center;
            color: #718096;
            font-size: 1.2em;
            margin-bottom: 30px;
        }

        .video-container {
            position: relative;
            width: 100%;
            max-width: 800px;
            margin: 30px auto;
            padding-bottom: 56.25%;
            height: 0;
            overflow: hidden;
            border-radius: 15px;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
        }

        .video-container iframe {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            border: none;
        }

        .section {
            margin-bottom: 35px;
            padding: 25px;
            background: #f8f9fa;
            border-radius: 15px;
            border-left: 5px solid #667eea;
        }

        h2 {
            color: #2d3748;
            font-size: 1.8em;
            margin-bottom: 15px;
            display: flex;
            align-items: center;
            gap: 10px;
        }

        h3 {
            color: #4a5568;
            font-size: 1.4em;
            margin-top: 25px;
            margin-bottom: 15px;
        }

        .icon {
            font-size: 1.2em;
        }

        p {
            color: #4a5568;
            margin-bottom: 15px;
            font-size: 1.05em;
        }

        .info-box {
            background: linear-gradient(135deg, #e3f2fd 0%, #bbdefb 100%);
            padding: 20px;
            border-radius: 12px;
            margin: 20px 0;
            border-left: 4px solid #2196f3;
        }

        .info-box strong {
            color: #1565c0;
            display: block;
            margin-bottom: 8px;
            font-size: 1.1em;
        }

        .success-box {
            background: linear-gradient(135deg, #e8f5e9 0%, #c8e6c9 100%);
            padding: 20px;
            border-radius: 12px;
            margin: 20px 0;
            border-left: 4px solid #4caf50;
        }

        .success-box strong {
            color: #2e7d32;
            display: block;
            margin-bottom: 8px;
            font-size: 1.1em;
        }

        .warning-box {
            background: linear-gradient(135deg, #fff3e0 0%, #ffe0b2 100%);
            padding: 20px;
            border-radius: 12px;
            margin: 20px 0;
            border-left: 4px solid #ff9800;
        }

        .warning-box strong {
            color: #e65100;
            display: block;
            margin-bottom: 8px;
            font-size: 1.1em;
        }

        pre {
            background: #2d3748;
            color: #f7fafc;
            padding: 20px;
            border-radius: 12px;
            overflow-x: auto;
            margin: 20px 0;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
        }

        code {
            font-family: 'Courier New', monospace;
            font-size: 0.95em;
            line-height: 1.6;
        }

        .keyword {
            color: #c792ea;
        }

        .function {
            color: #82aaff;
        }

        .string {
            color: #c3e88d;
        }

        .comment {
            color: #546e7a;
            font-style: italic;
        }

        .highlight {
            background: linear-gradient(135deg, #ffeaa7 0%, #fdcb6e 100%);
            padding: 3px 8px;
            border-radius: 5px;
            font-weight: 600;
        }

        .visual-demo {
            background: white;
            padding: 30px;
            border-radius: 12px;
            margin: 25px 0;
            text-align: center;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
        }

        .checkbox-demo {
            display: inline-flex;
            align-items: center;
            gap: 10px;
            margin: 10px 20px;
            padding: 12px 20px;
            background: #f8f9fa;
            border-radius: 8px;
            cursor: pointer;
            transition: all 0.3s ease;
        }

        .checkbox-demo:hover {
            background: #e9ecef;
            transform: scale(1.05);
        }

        .checkbox-square {
            width: 20px;
            height: 20px;
            border: 2px solid #667eea;
            border-radius: 4px;
            position: relative;
            transition: all 0.3s ease;
        }

        .checkbox-square.checked {
            background: #667eea;
        }

        .checkbox-square.checked::after {
            content: '✓';
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            color: white;
            font-weight: bold;
            font-size: 14px;
        }

        .comparison-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
            gap: 20px;
            margin: 25px 0;
        }

        .comparison-card {
            background: white;
            padding: 25px;
            border-radius: 12px;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
            transition: transform 0.3s ease;
        }

        .comparison-card:hover {
            transform: translateY(-5px);
            box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
        }

        .comparison-card h4 {
            color: #667eea;
            font-size: 1.3em;
            margin-bottom: 15px;
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .key-concept {
            background: linear-gradient(135deg, #f3e5f5 0%, #e1bee7 100%);
            padding: 20px;
            border-radius: 12px;
            margin: 20px 0;
            border-left: 4px solid #9c27b0;
        }

        .key-concept strong {
            color: #6a1b9a;
            display: block;
            margin-bottom: 10px;
            font-size: 1.1em;
        }

        .flow-diagram {
            background: white;
            padding: 25px;
            border-radius: 12px;
            margin: 20px 0;
            text-align: center;
        }

        .flow-step {
            display: inline-block;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 12px 20px;
            border-radius: 8px;
            margin: 5px;
            font-weight: 600;
        }

        .flow-arrow {
            display: inline-block;
            font-size: 1.5em;
            color: #667eea;
            margin: 0 10px;
        }

        .step-card {
            background: white;
            padding: 20px;
            border-radius: 12px;
            margin: 15px 0;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
            border-left: 4px solid #667eea;
        }

        .step-number {
            display: inline-block;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            width: 35px;
            height: 35px;
            border-radius: 50%;
            text-align: center;
            line-height: 35px;
            font-weight: bold;
            margin-right: 10px;
            font-size: 1.1em;
        }

        .navigation {
            display: flex;
            justify-content: space-between;
            margin-top: 40px;
            gap: 20px;
        }

        .nav-button {
            flex: 1;
            padding: 15px 25px;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            text-decoration: none;
            border-radius: 12px;
            text-align: center;
            font-weight: 600;
            transition: transform 0.3s ease, box-shadow 0.3s ease;
            box-shadow: 0 4px 15px rgba(102, 126, 234, 0.3);
        }

        .nav-button:hover {
            transform: translateY(-3px);
            box-shadow: 0 8px 25px rgba(102, 126, 234, 0.5);
        }

        .code-highlight {
            background: #fff3cd;
            color: #856404;
            padding: 2px 6px;
            border-radius: 4px;
            font-family: 'Courier New', monospace;
            font-size: 0.9em;
        }

        @media (max-width: 768px) {
            .container {
                padding: 25px 20px;
            }

            h1 {
                font-size: 2em;
            }

            h2 {
                font-size: 1.4em;
            }

            .section {
                padding: 20px 15px;
            }

            pre {
                padding: 15px;
                font-size: 0.85em;
            }

            .comparison-grid {
                grid-template-columns: 1fr;
            }

            .navigation {
                flex-direction: column;
            }

            .flow-diagram {
                padding: 15px;
            }

            .flow-step {
                display: block;
                margin: 10px 0;
            }

            .flow-arrow {
                display: block;
                transform: rotate(90deg);
            }
        }