body {
            margin: 0;
            font-family: Arial, sans-serif;
            background-color: #f4f4f4;
        }

        header {
            background-color: #202945;
            padding: 10px 20px;
            display: flex;
            align-items: center;
        }

        .logo {
            width: 240px;
        }

        .container {
            display: flex;
            height: calc(100vh - 60px);
        }

        .sidebar {
            width: 260px;
            background-color: #eceff1;
            padding: 20px;
            overflow-y: auto;
        }

        .sidebar h3 {
            font-size: 14px;
            margin-top: 20px;
            color: #333;
        }

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

        .sidebar .menu-item {
            padding: 8px 12px;
            margin: 4px 0;
            background-color: #fff;
            border: 1px solid #ccc;
            border-radius: 4px;
            cursor: pointer;
            font-size: 14px;
        }

        .sidebar .menu-item:hover {
            background-color: #00A0DE;
            color: #fff;
        }

        main {
            flex: 1;
            display: flex;
            flex-direction: row;
            padding: 20px;
            gap: 20px;
        }

        .content-area {
            flex: 3;
            background-color: #fff;
            padding: 20px;
            border-radius: 8px;
            overflow-y: auto;
        }

        #content-area * img {
            display: block;
            margin-left: auto;
            margin-right: auto;
            margin-top: 20px;
            margin-bottom: 20px;
        }

        .doc-panel {
            flex: 1;
            background-color: #f9f9f9;
            border-left: 1px solid #ddd;
            padding: 20px;
            border-radius: 8px;
        }

        .btn-download {
            display: inline-block;
            margin-top: 12px;
            padding: 10px 20px;
            background-color: #00A0DE;
            color: white;
            text-decoration: none;
            border-radius: 4px;
        }

        .btn-download:hover {
            background-color: #007eae;
        }