* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: "Microsoft Yahei", Arial, sans-serif;
        }
        
        body {
            line-height: 1.6;
            color: #333;
            background-color: #f5f5f5;
        }
        
        /* 导航栏优化 */
        header {
            background: #fff;
            box-shadow: 0 2px 10px rgba(0,0,0,0.05);
            position: sticky;
            top: 0;
            z-index: 999;
        }
        
        .navbar-container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 5%;
            display: flex;
            justify-content: space-between;
            align-items: center;
            height: 70px;
        }
        
        .nav-brand {
            display: flex;
            align-items: center;
            text-decoration: none;
            color: #333;
            font-weight: 600;
            font-size: clamp(1rem, 2vw, 1.25rem);
            z-index: 1000;
        }
        
        .nav-brand img {
            height: clamp(2rem, 4vw, 3rem);
            margin-right: 0.8rem;
        }
        
        /* 汉堡菜单按钮 */
        .menu-toggle {
            display: none;
            flex-direction: column;
            cursor: pointer;
            z-index: 1000;
        }
        
        .bar {
            width: 22px;
            height: 2.5px;
            background-color: #333;
            margin: 3px 0;
            transition: 0.3s;
            border-radius: 3px;
        }
        
        /* 导航链接容器 */
        .nav-links {
            display: flex;
            gap: 1.5rem;
            align-items: center;
        }
        
        .nav-links a {
            color: #333;
            text-decoration: none;
            font-size: clamp(0.9rem, 1.5vw, 1rem);
            position: relative;
            padding: 0.5rem 0;
        }
        
        .nav-links a:hover {
            color: #007bff;
        }
        
        .nav-links a::after {
            content: '';
            position: absolute;
            bottom: 0;
            left: 0;
            width: 0;
            height: 2px;
            background: #007bff;
            transition: width 0.3s;
        }
        
        .nav-links a:hover::after {
            width: 100%;
        }
        
        /* 主容器 */
        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 2rem 5%;
        }
        
        /* 视频播放器 */
        .video-player {
            width: 100%;
            margin-bottom: 2rem;
            border-radius: 10px;
            overflow: hidden;
            box-shadow: 0 10px 25px rgba(0,0,0,0.1);
            background: #000;
        }
        
        #videoPlayer {
            width: 100%;
            height: auto;
            max-height: 500px;
            display: block;
            margin: 0 auto;
        }
        
        #errorMsg {
            color: #dc3545;
            padding: 1rem;
            background: #f8d7da;
            border-radius: 8px;
            margin-bottom: 1rem;
            display: none;
        }
        
        /* 视频信息 */
        .video-info {
            background: #fff;
            padding: 1.5rem;
            border-radius: 10px;
            box-shadow: 0 5px 15px rgba(0,0,0,0.05);
            margin-bottom: 2rem;
        }
        
        /* 标题字体大小与课程列表标题一致 */
        .video-title {
            font-size: clamp(1.1rem, 2vw, 1.5rem);
            margin-bottom: 0.8rem;
            color: #212529;
        }
        
        .video-description {
            font-size: clamp(0.95rem, 1.5vw, 1rem);
            color: #6c757d;
            line-height: 1.7;
        }
        
        /* 课程列表 */
        .episodes-container {
            background: #fff;
            padding: 1.5rem;
            border-radius: 10px;
            box-shadow: 0 5px 15px rgba(0,0,0,0.05);
            margin-bottom: 2rem;
        }
        
        .episodes-header {
            font-size: clamp(1.1rem, 2vw, 1.5rem);
            margin-bottom: 1rem;
            padding-bottom: 0.5rem;
            border-bottom: 2px solid #007bff;
            color: #212529;
        }
        
        .episodes-list {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
            gap: 1rem;
        }
        
        /* 课程项样式 */
        .episode-item {
            background: #fafafa;
            border: 1px solid #e9ecef;
            border-radius: 8px;
            padding: 0.8rem;
            transition: all 0.3s;
            cursor: pointer;
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;
            text-align: center;
            height: 100%;
        }
        
        .episode-item:hover {
            transform: translateY(-3px);
            box-shadow: 0 8px 15px rgba(0,0,0,0.1);
            border-color: #007bff;
        }
        
        .episode-item img {
            width: 100%;
            height: 120px;
            object-fit: cover;
            border-radius: 4px;
            margin-bottom: 0.5rem;
        }
        
        .episode-title {
            font-size: 0.9rem;
            color: #333;
            font-weight: 500;
        }
        
        /* 文件下载 */
        .file-item {
            display: flex;
            align-items: center;
            padding: 1rem;
            border: 1px solid #e9ecef;
            border-radius: 8px;
            transition: all 0.3s;
            background: #fafafa;
            margin-top: 1rem;
        }
        
        .file-item:hover {
            transform: translateY(-3px);
            box-shadow: 0 8px 15px rgba(0,0,0,0.1);
            border-color: #007bff;
        }
        
        .file-item img {
            height: clamp(2rem, 4vw, 3rem);
            margin-right: 1rem;
        }
        
        .info {
            flex: 1;
            font-size: clamp(0.95rem, 1.5vw, 1rem);
        }
        
        .download-btn {
            display: inline-block;
            padding: 0.5rem 1.25rem;
            background: #007bff;
            color: #fff;
            text-decoration: none;
            border-radius: 6px;
            transition: background 0.3s;
            cursor: pointer;
        }
        
        .download-btn:hover {
            background: #0056b3;
        }
        
        /* 页脚 */
        footer {
            background: #343a40;
            color: #fff;
            text-align: center;
            padding: 2rem 5%;
            margin-top: 3rem;
        }
        
        /* 响应式调整 */
        @media (max-width: 768px) {
            .navbar-container {
                height: 70px;
                position: relative;
            }
            
            .menu-toggle {
                display: flex;
            }
            
            .nav-links {
                position: fixed;
                top: 0;
                right: -100%;
                height: 100vh;
                width: 200px;
                background-color: #fff;
                flex-direction: column;
                justify-content: flex-start;
                padding-top: 80px;
                gap: 1.5rem;
                box-shadow: -2px 0 10px rgba(0,0,0,0.1);
                transition: 0.3s ease;
                z-index: 999;
            }
            
            .nav-links.active {
                right: 0;
            }
            
            .nav-links a {
                font-size: 0.95rem;
                padding: 0.3rem 1rem;
                width: 100%;
                text-align: center;
            }
            
            .episodes-list {
                grid-template-columns: repeat(2, 1fr);
                gap: 0.8rem;
            }
            
            .episode-item {
                padding: 0.5rem;
            }
            
            .episode-item img {
                height: 80px;
            }
            
            .episode-title {
                font-size: 0.8rem;
            }
            
            #videoPlayer {
                max-height: 220px;
            }
            
            .file-item {
                flex-direction: column;
                text-align: center;
                gap: 1rem;
                padding: 1.2rem;
            }
            
            .file-item img {
                margin-right: 0;
            }
            
            .download-btn {
                width: 100%;
                text-align: center;
            }
        }
        
        .loading {
            text-align: center;
            padding: 2rem;
            color: #6c757d;
            grid-column: 1 / -1;
        }