.layout {
        display: flex;
        align-items: flex-start; /* 顶部对齐 */
      }

      .sidebar {
        position: sticky; /* 粘性定位 */
        top: 60px;      /* 确保侧边栏总是在距离视口顶部 70px 的位置，避开导航栏 */
        width: 250px;
        background-color: #fff2df;
        padding: 2rem;
        z-index: 1;     /* 设置 z-index，保证不会遮挡或被遮挡 */
        width: 250px;
            /* 调整视距长度 */
        height: 92vh;      
      }

      .main-content {
        flex: 1;
        padding: 2rem;
      }

      
        .sidebar-menu {
            list-style: none;
        }

        .sidebar-menu li {
            margin-bottom: 1rem;
            position: relative;
        }

        .sidebar-menu a {
            display: flex;
            justify-content: space-between;
            align-items: center;
            color: var(--text-color);
            text-decoration: none;
            padding: 8px 12px;
            border-radius: 4px;
            transition: all 0.3s ease;
            background-color: transparent;
            width: 200px;
            font-size: 19px;
        }

        .has-submenu > a::after {
            content: '▼';
            font-size: 0.8em;
            margin-left: 8px;
            transition: transform 0.3s ease;
        }

        .has-submenu.active > a::after {
            transform: rotate(180deg);
        }

        .sidebar-menu a:hover {
            background-color: #FFE4C4;
            color: #8B4513;
        }

        .submenu {
            list-style: none;
            position: static;
            background-color: transparent;
            border: none;
            border-radius: 4px;
            padding: 0;
            margin-left: 12px;
            min-width: 120px;
            max-height: 0;
            overflow: hidden;
            transition: all 0.3s ease-in-out;
            opacity: 0;
        }

        .sidebar-menu li.active > .submenu {
            display: block;
            max-height: 500px;
            padding: 4px 0;
            opacity: 1;
        }

        .submenu li {
            margin-bottom: 0.3rem;
            transform: translateX(-10px);
            opacity: 0;
            transition: all 0.3s ease-in-out;
        }

        .sidebar-menu li.active > .submenu li {
            transform: translateX(0);
            opacity: 1;
            transition-delay: 0.2s;
        }

        .submenu a {
            padding: 4px 12px;
            font-size: 16px;
            white-space: nowrap;
            border-left: 2px solid #DEB887;
            margin-left: 10px;
            width: auto;
            transition: all 0.3s ease;
        }

        .submenu a:hover {
            background-color: #FFE4C4;
            color: #8B4513;
            border-left: 2px solid #8B4513;
        }

        
        .lab-section {
            background-color: #bf8d4e;
            color: var(--white);
            padding: 1rem;
            margin-bottom: 0;
            border-radius: 4px 4px 0 0;
            cursor: pointer;
            display: flex;
            justify-content: space-between;
            align-items: center;
            transition: background-color 0.3s ease;
        }

        /* .lab-section:hover {
            background-color: #ffde7d;
        } */

        .lab-section::after {
            content: '▼';
            font-size: 0.8em;
            transition: transform 0.3s ease;
        }

        .lab-section.active::after {
            transform: rotate(180deg);
        }

        .lab-content {
            font-family: Georgia, 'Times New Roman', Times, serif;
             
            background-color: white;
            padding: 0;
            margin-top: -1rem;
            margin-bottom: 1rem;
            border: 1px solid #ddd;
            border-top: none;
            border-radius: 0 0 4px 4px;
            max-height: 0;
            overflow: hidden;
            transition: all 0.3s ease;
        }

        .lab-content.active {
            padding: 1rem;
            max-height: 10000px;
        }

        .main-content h2 {
            margin: 2rem 0 1rem 0;
            color: #3d3939;
        }

        .main-content h3 {
            color: black;
            /* margin-bottom: 0.5rem; */
            margin-bottom: 10px;
            text-align: center;
            font-size: 25px;
        }

        h1{
            font-size: 32px;
            margin-top: 70px;
        }