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

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            line-height: 1.8;
            color: #333;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            padding: 20px;
        }

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

        header {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 40px;
            text-align: center;
        }

        header h1 {
            font-size: 2.5em;
            margin-bottom: 10px;
        }

        header p {
            font-size: 1.2em;
            opacity: 0.9;
        }

        nav {
            background: #f8f9fa;
            padding: 20px 40px;
            border-bottom: 2px solid #e9ecef;
        }

        nav a {
            color: #667eea;
            text-decoration: none;
            font-size: 1.1em;
            transition: color 0.3s;
        }

        nav a:hover {
            color: #764ba2;
        }

        .content {
            padding: 40px;
        }

        .intro-section {
            background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
            padding: 30px;
            border-radius: 15px;
            margin-bottom: 40px;
        }

        .intro-section h2 {
            color: #667eea;
            margin-bottom: 20px;
            font-size: 2em;
        }

        .intro-section h3 {
            color: #667eea;
            margin-top: 25px;
            margin-bottom: 15px;
            font-size: 1.4em;
        }

        .intro-section p {
            font-size: 1.1em;
            line-height: 1.8;
            margin-bottom: 15px;
        }

        .course-intro {
            background: #fff;
            padding: 30px;
            border-radius: 15px;
            margin-bottom: 40px;
            border-left: 5px solid #667eea;
        }

        .course-intro h2 {
            color: #667eea;
            margin-bottom: 20px;
            font-size: 1.8em;
        }

        .course-intro h3 {
            color: #667eea;
            margin-bottom: 15px;
            font-size: 1.5em;
        }

        .course-intro p {
            margin-bottom: 15px;
        }

        .sections {
            margin-top: 30px;
        }

        .section {
            background: #fff;
            border: 2px solid #e9ecef;
            border-radius: 15px;
            padding: 30px;
            margin-bottom: 30px;
            transition: transform 0.3s, box-shadow 0.3s;
        }

        .section:hover {
            transform: translateY(-5px);
            box-shadow: 0 10px 30px rgba(102, 126, 234, 0.2);
        }

        .section-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 20px;
        }

        .section-info h4 {
            color: #667eea;
            font-size: 1.5em;
            margin-bottom: 10px;
        }

        .section-info p {
            color: #666;
            font-size: 1.05em;
        }

        .download-btn {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 12px 30px;
            border-radius: 25px;
            text-decoration: none;
            display: inline-flex;
            align-items: center;
            gap: 10px;
            transition: transform 0.3s, box-shadow 0.3s;
            font-weight: bold;
        }

        .download-btn:hover {
            transform: scale(1.05);
            box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
        }

        .exercises {
            background: #f8f9fa;
            padding: 25px;
            border-radius: 10px;
            margin-top: 20px;
        }

        .exercises h5 {
            color: #667eea;
            margin-bottom: 15px;
            font-size: 1.3em;
        }

        .exercise-item {
            background: white;
            padding: 20px;
            border-radius: 8px;
            margin-bottom: 15px;
            border-left: 4px solid #667eea;
        }

        .exercise-item:last-child {
            margin-bottom: 0;
        }

        .exercise-item h6 {
            color: #333;
            margin-bottom: 10px;
            font-size: 1.1em;
        }

        .exercise-item p {
            color: #666;
            line-height: 1.6;
        }

        footer {
            background: #2c3e50;
            color: white;
            text-align: center;
            padding: 20px;
        }

        @media (max-width: 768px) {
            .section-header {
                flex-direction: column;
                align-items: flex-start;
            }

            header h1 {
                font-size: 1.8em;
            }

            .content {
                padding: 20px;
            }
        }