@keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }
        @keyframes fadeInUp { from { opacity: 0; transform: translateY(30px); } to { opacity: 1; transform: translateY(0); } }
        @keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
        
        .video-wrapper { position: relative; display: inline-block; width: 100%; max-width: 100%; }
        .chamelearn-lesson-button-container { text-align: center; margin: 30px auto 20px; padding: 30px 25px; background: linear-gradient(135deg, #eff6ff 0%, #dbeafe 100%); border-radius: 24px; border: 2px solid #bfdbfe; box-shadow: 0 10px 35px rgba(102, 126, 234, 0.15); max-width: 650px; width: 95%; animation: fadeInUp 0.6s ease; }
        .sm-start-lesson-btn { padding: 16px 40px; background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); color: white; border: none; border-radius: 50px; font-size: 20px; font-weight: 800; cursor: pointer; box-shadow: 0 10px 30px rgba(102, 126, 234, 0.4); transition: all 0.3s; display: inline-flex; align-items: center; justify-content: center; gap: 12px; width: 100%; max-width: 400px; }
        .sm-start-lesson-btn:hover { transform: translateY(-4px) scale(1.03); box-shadow: 0 15px 40px rgba(102, 126, 234, 0.6); color: white; }
        .sm-close-btn:hover { transform: scale(1.1) rotate(90deg) !important; }
        .section-card { background: white; border-radius: 20px; padding: 30px 25px; box-shadow: 0 4px 15px rgba(0,0,0,0.08); border: 2px solid #e2e8f0; transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1); cursor: pointer; }
        .section-card:hover { transform: translateY(-6px); box-shadow: 0 12px 30px rgba(102, 126, 234, 0.15); border-color: #667eea; }
        .section-card[data-completed="true"] { border-color: #10b981; }
        .section-card[data-completed="true"]:hover { transform: none; }
        .action-btn { width: 100%; padding: 14px; border: none; border-radius: 14px; font-weight: 700; font-size: 16px; cursor: pointer; transition: all 0.2s; display: flex; align-items: center; justify-content: center; gap: 8px; }
        .action-btn:hover { transform: translateY(-2px); box-shadow: 0 6px 15px rgba(0,0,0,0.15); }
        
        @media (max-width: 768px) {
            .chamelearn-lesson-button-container { max-width: 100% !important; margin: 20px 10px !important; padding: 25px 20px !important; }
            .sm-start-lesson-btn { width: 100%; font-size: 18px !important; padding: 14px 30px !important; }
            .section-card { padding: 25px 20px !important; }
            .chamelearn-student-interface { padding: 10px !important; }
        }

@keyframes spin { to { transform: rotate(360deg); } }