body, html {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            margin: 0;
            padding: 0;
            height: 100%;
            background-color: #f0f2f5;
        }

        .container {
            display: flex;
            height: 100%;
        }

        .sidebar {
            width: 280px;
            background-color: #ffffff;
            box-shadow: 2px 0 5px rgba(0, 0, 0, 0.1);
            padding: 20px;
            overflow-y: auto;
            transition: transform 0.3s ease-in-out;
            z-index: 10;
        }

        .sidebar.hidden {
            transform: translateX(-100%);
        }

        .content {
            flex: 1;
            padding: 20px;
            display: flex;
            flex-direction: column;
            align-items: center;
            overflow-y: auto;
        }

        .content-wrapper {
            display: flex;
            width: 100%;
            max-width: 1600px;
            gap: 20px;
            flex-wrap: wrap;
        }

        .sidebar h2 {
            margin-top: 0;
            margin-left: 50px;
            padding-bottom: 15px;
            border-bottom: 2px solid #e0e0e0;
            color: #333;
        }

        .sidebar ul {
            list-style-type: none;
            padding: 0;
        }

        .sidebar li {
            padding: 12px 15px;
            cursor: pointer;
            border-radius: 5px;
            margin-bottom: 5px;
            transition: background-color 0.3s;
        }

        .sidebar li:hover {
            background-color: #f0f0f0;
        }

        .sidebar li.active {
            background-color: #e0e0e0;
            font-weight: bold;
        }

        .video-container {
            flex: 1;
            min-width: 300px;
            background-color: #fff;
            border-radius: 10px;
            box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
            overflow: hidden;
            margin-bottom: 20px;
            transition: opacity 0.3s ease-in-out;
        }

        .video-container:nth-child(2) {
            display: none;
            opacity: 0;
        }

        .video-player {
            width: 100%;
            background-color: #000;
        }

        .video-controls {
            padding: 15px;
            background-color: #fff;
            display: flex;
            align-items: center;
            flex-wrap: wrap;
        }

        .video-controls button {
            background: none;
            border: none;
            color: #333;
            font-size: 18px;
            cursor: pointer;
            margin-right: 15px;
            transition: color 0.3s;
        }

        .video-controls button:hover {
            color: #007bff;
        }

        .seek-bar {
            flex-grow: 1;
            height: 6px;
            margin: 0 15px;
            -webkit-appearance: none;
            background: #e0e0e0;
            outline: none;
            border-radius: 3px;
            transition: background 0.2s;
        }

        .seek-bar::-webkit-slider-thumb {
            -webkit-appearance: none;
            appearance: none;
            width: 15px;
            height: 15px;
            border-radius: 50%;
            background: #007bff;
            cursor: pointer;
        }

        .seek-bar::-moz-range-thumb {
            width: 15px;
            height: 15px;
            border-radius: 50%;
            background: #007bff;
            cursor: pointer;
        }

        .time-display {
            color: #666;
            font-size: 14px;
            margin-left: 15px;
        }

        select {
            background-color: #f0f0f0;
            color: #333;
            border: none;
            padding: 5px 10px;
            margin-left: 15px;
            border-radius: 3px;
            cursor: pointer;
        }

        .pdf-container {
            flex: 1;
            min-width: 300px;
            height: 600px;
            position: relative;
            display: none;
        }

        #pdfViewer {
            width: 100%;
            height: 100%;
            border: none;
            border-radius: 10px;
            box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
        }

        .close-pdf-btn {
            position: absolute;
            top: 10px;
            right: 10px;
            background-color: rgba(0, 0, 0, 0.5);
            color: white;
            border: none;
            border-radius: 50%;
            width: 30px;
            height: 30px;
            font-size: 20px;
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: center;
            transition: background-color 0.3s;
        }

        .close-pdf-btn:hover {
            background-color: rgba(0, 0, 0, 0.7);
        }

        #fileInput {
            display: none;
        }

        .add-content-btn {
            display: block;
            width: 100%;
            padding: 10px;
            background-color: #007bff;
            color: white;
            text-align: center;
            cursor: pointer;
            border-radius: 5px;
            margin-top: 20px;
        }

        .add-content-btn:hover {
            background-color: #0056b3;
        }

        .toggle-sidebar-btn {
            position: fixed;
            top: 20px;
            left: 20px;
            z-index: 1000;
            background-color: #007bff;
            color: white;
            border: none;
            padding: 10px 15px;
            font-size: 20px;
            cursor: pointer;
            border-radius: 5px;
            transition: background-color 0.3s;
        }

        .toggle-sidebar-btn:hover {
            background-color: #0056b3;
        }

        .video-container {
            flex: 1;
            min-width: 300px;
            background-color: #fff;
            border-radius: 10px;
            box-shadow: 0 4px 6px rgba(0,0,0,0.1);
            overflow: hidden;
            margin-bottom: 20px;
            transition: opacity 0.3s ease-in-out;
            display: none;
            opacity: 0;
        }
        .video-container.active {
            display: block;
            opacity: 1;
        }
        .close-video-btn {
            position: absolute;
            top: 10px;
            right: 10px;
            background-color: rgba(0, 0, 0, 0.5);
            color: white;
            border: none;
            border-radius: 50%;
            width: 30px;
            height: 30px;
            font-size: 20px;
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: center;
            transition: background-color 0.3s;
        }
        .close-video-btn:hover {
            background-color: rgba(0, 0, 0, 0.7);
        }