/* 通用样式 */
        body {
            margin: 0;
            font-family: Arial, sans-serif;
        }

        .back-button {
            margin-left: auto;
            cursor: pointer;
        }

        .back-button i {
            color: white;
            font-size: 20px;
        }

        .main-container {
            display: flex;
            flex: 1;
            gap: 0;
            overflow: hidden;
            padding: 0;
        }

        .column {
            border: none;
            border-radius: 0;
            box-shadow: none;
            overflow-y: auto;
        }

        .version-column {
            width: 24%;
            background-color: #ffebd5;
            height: calc(100vh - 160px);
        }

        .grade-column {
            width: 27%;
            background-color: #fff4e5;
            height: calc(100vh - 160px);
        }

        .unit-column {
            width: 49%;
            background-color: #f8f8f8;
            height: calc(100vh - 160px);
        }

        .version-item,
        .grade-item {
            padding: 18px 8px;
            margin: 0;
            border-radius: 0;
            font-size: 17px;
            font-weight: 500;
            border: none;
            transition: all 0.3s ease;
            background-color: transparent;
        }

        /* 未选中的版本文字颜色改为白色 */
        .version-item:not(.active) {
            color: gray;
        }

        /* 未选中的年级文字颜色改为绿色 */
        .grade-item:not(.active) {
            color: gray;
        }

        .version-item:hover,
        .grade-item:hover {
            background-color: rgba(255, 255, 255, 0.1);
            border-color: transparent;
            box-shadow: none;
            transform: none;
        }

        .unit-link {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 10px;
            padding: 10px;
            margin: 0;
            border-radius: 0;
            border: none;
            transition: all 0.3s ease;
            text-decoration: none;
            color: #333;
            background-color: #f8f8f8;
        }

        .unit-thumb {
            width: 100%;
            height: 100%; /* 固定图片容器高度 */
            background: #f0f0f0;
            border-radius: 0;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .unit-thumb img {
            max-width: 100%;
            max-height: 100%;
            object-fit: contain;
        }

        .unit-content {
            text-align: center;
            width: 100%; /* 确保按钮容器占满宽度 */
        }

        .unit-title {
            font-size: 16px;
            margin-bottom: 10px;
        }

        .unit-description {
            font-size: 15px;
            color: #777;
        }

        /* 新增课标题样式 */
        .lesson-title {
            font-size: 15px;
            line-height: 1.5;
            display: block;
            margin-bottom: 5px;
        }

        /* 课程按钮样式 */
        .lesson-button {
            display: block;
            width: 100%;
            padding: 12px 24px;
            margin-bottom: 10px;
            border: none;
            border-radius: 25px; /* 优化圆角比例 */
            background-color: #ffe3c5;
            color: gray;
            font-size: 14px;
            cursor: pointer;
            transition: background-color 0.3s ease, transform 0.2s ease;
            box-sizing: border-box; /* 确保内边距不影响宽度 */
            max-width: 100%; /* 防止文字过长溢出 */
        }

        .lesson-button:hover {
            background-color: #ffd9b1;
            transform: translateY(-1px);
            box-shadow: 0 2px 4px rgba(255, 153, 0, 0.2);
        }

        .active {
            background-color: white;
            color: #ff9900;
            box-shadow: none;
            transform: none;
        }

        .version-item.active:hover,
        .grade-item.active:hover {
            background-color: white;
            box-shadow: none;
        }

        .bottom-button a {
            display: flex;
            flex-direction: column;
            align-items: center;
            text-decoration: none;
            color: #ff9900;
            transition: color 0.3s ease;
        }

        .bottom-button a:hover {
            color: #e68a00;
        }

        .bottom-button i {
            font-size: 26px;
        }

        /* 底部栏样式 */
        .bottom-bar {
            display: flex;
            justify-content: space-around;
            background-color: white;
            padding: 10px 0;
        }

        /* 头部样式 */
        .header.bottom {
            width: 100%;
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 20px;
            background-color: #fff;
            color: white;
			border-bottom: 1px solid #ccc;
        }

        .header.bottom img {
            height: 30px;
        }

        .header.bottom a {
            color: #ff9900;
            text-decoration: none;
            margin-left: auto;
        }