.container {
            max-width: 900px;
            margin: 0 auto;
            background-color: #fff;
            min-height: 100vh;
            box-shadow: 0 0 20px rgba(0,0,0,0.1);
        }

        /* Sticky Header */
        .header {
            position: sticky;
            top: 0;
            background-color: #f8f9fa;
            padding: 25px 30px;
            display: flex;
            align-items: center;
            gap: 15px;
            box-shadow: 0 2px 5px rgba(0,0,0,0.1);
            z-index: 100;
        }

        .back-btn {
            background-color: #fff;
            border: 1px solid #ddd;
            width: 40px;
            height: 40px;
            cursor: pointer;
            transition: all 0.3s;
            border-radius: 8px;
            display: flex;
            align-items: center;
            justify-content: center;
            box-shadow: 0 2px 4px rgba(0,0,0,0.1);
        }

        .back-btn:hover {
            background-color: #f0f0f0;
            transform: translateX(-2px);
        }

        .back-btn img {
            width: 20px;
            height: 20px;
        }

        .header-title {
            font-size: 25px;
            font-weight: 600;
            color: #333;
        }

        /* Content Section */
        .content {
            padding: 30px 20px;
        }

        .intro-text {
            margin-bottom: 30px;
            font-size: 16px;
            color: #555;
            line-height: 1.8;
        }

        /* Accordion Styles */
        .accordion {
            background: #fff;
            border-radius: 8px;
            overflow: hidden;
            box-shadow: 0 1px 3px rgba(0,0,0,0.1);
        }

        .accordion-item {
            border-bottom: 1px solid #e0e0e0;
        }

        .accordion-item:last-child {
            border-bottom: none;
        }

        .accordion-header {
            background: #fff;
            padding: 18px 20px;
            cursor: pointer;
            display: flex;
            justify-content: space-between;
            align-items: center;
            transition: background 0.2s;
        }

        .accordion-header:hover {
            background: #f9f9f9;
        }

        .accordion-header.active {
            background: #f0f0f0;
        }

        .chapter-title {
            font-size: 18px;
            font-weight: 600;
            color: #0066CC;
        }

        .accordion-icon {
            font-size: 20px;
            color: #666;
            transition: transform 0.3s;
        }

        .accordion-header.active .accordion-icon {
            transform: rotate(180deg);
        }

        .accordion-content {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.3s ease;
            background: #fafafa;
        }

        .accordion-content.active {
            max-height: 1200px;
        }

        .sub-chapter {
            padding: 12px 20px 12px 40px;
            cursor: pointer;
            border-top: 1px solid #e8e8e8;
            display: flex;
            align-items: center;
            transition: background 0.2s;
        }

        .sub-chapter:hover {
            background: #f0f0f0;
        }

        .play-icon {
            margin-right: 10px;
            color: #4CAF50;
        }

        .sub-chapter-title {
            color: #555;
            font-size: 14px;
        }

        /* Modal Styles */
        .modal {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background: rgba(0,0,0,0.9);
            z-index: 2000;
            justify-content: center;
            align-items: center;
        }

        .modal.active {
            display: flex;
        }

        .modal-content {
            position: relative;
            width: 90%;
            max-width: 900px;
            background: #000;
            border-radius: 8px;
            overflow: hidden;
        }

        .close-btn {
            position: absolute;
            top: 10px;
            right: 10px;
            background: rgba(255,255,255,0.9);
            border: none;
            border-radius: 50%;
            width: 40px;
            height: 40px;
            font-size: 24px;
            cursor: pointer;
            z-index: 10;
            display: flex;
            align-items: center;
            justify-content: center;
            transition: background 0.2s;
        }

        .close-btn:hover {
            background: #fff;
        }

        .video-player {
            width: 100%;
            display: block;
            max-height: 80vh;
        }

        /* Footer */
        .footer {
            text-align: center;
            padding: 30px 20px;
            color: #888;
            font-size: 14px;
        }
		
		/* Floating Subscribe Button */
        .subscribe-btn {
            position: fixed;
            bottom: 30px;
            right: 30px;
            background-color: #ff4757;
            color: #fff;
            border: none;
            padding: 15px 30px;
            border-radius: 50px;
            font-size: 16px;
            font-weight: 600;
            cursor: pointer;
            box-shadow: 0 4px 15px rgba(255,71,87,0.4);
            transition: all 0.3s;
            z-index: 99;
        }

        .subscribe-btn:hover {
            background-color: #ff3838;
            transform: translateY(-3px);
            box-shadow: 0 6px 20px rgba(255,71,87,0.5);
        }

        /* Responsive */
        @media (max-width: 768px) {
            .container {
                padding: 15px;
            }

            .header-title {
                font-size: 18px;
            }

            .chapter-title {
                font-size: 18px;
            }

            .sub-chapter-title {
                font-size: 13px;
            }

            .modal-content {
                width: 95%;
            }
        }

        @media (max-width: 480px) {
            .header {
                padding: 0 15px;
            }

            .accordion-header {
                padding: 15px;
            }

            .sub-chapter {
                padding: 10px 15px 10px 30px;
            }
        }