:root {
            --main-color: #333;
            --active-color: #FF9800; /* 修改为暖橙色 */
            --active-light: #FFF3E0; /* 浅橙色背景 */
            --bg-color: #ffffff;
            --border-color: #f0f0f0;
        }

        body {
            margin: 0;
            background-color: #f5f5f5;
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
            color: var(--main-color);
        }

        .app-wrapper {
            max-width: 500px;
            margin: 0 auto;
            background-color: var(--bg-color);
            min-height: 100vh;
        }

        /* 顶部标题栏 */
        .top-bar {
            padding: 12px;
            text-align: center;
            font-size: 18px;
            font-weight: bold;
            color: var(--active-color);
            border-bottom: 1px solid var(--border-color);
        }

        /* 搜索框 */
        .search-area {
            padding: 10px 15px;
            display: flex;
        }

        .search-area input {
            flex: 1;
            padding: 8px 12px;
            border: 1px solid #ddd;
            border-radius: 4px 0 0 4px;
            font-size: 14px;
            outline: none;
            background: #f9f9f9;
        }

        .search-area button {
            padding: 0 15px;
            background: var(--active-color);
            color: white;
            border: none;
            border-radius: 0 4px 4px 0;
            font-size: 14px;
        }

        /* --- 优化的 Tab 导航栏 --- */
        .nav-container {
            display: flex;
            align-items: center;
            border-bottom: 1px solid var(--border-color);
            background: #fff;
            position: sticky;
            top: 0;
            z-index: 10;
        }

        .tab-wrapper {
            flex: 1;
            display: flex;
            overflow-x: auto;
            white-space: nowrap;
            -webkit-overflow-scrolling: touch;
            padding: 0 10px;
        }

        .tab-wrapper::-webkit-scrollbar {
            display: none;
        }

        .tab-item {
            padding: 12px 15px;
            font-size: 15px;
            color: #666;
            text-decoration: none;
            position: relative;
            display: inline-block;
        }

        .tab-item.active {
            color: var(--active-color);
            font-weight: bold;
        }

        /* 选中态的下划线 */
        .tab-item.active::after {
            content: "";
            position: absolute;
            bottom: 0;
            left: 20%;
            right: 20%;
            height: 3px;
            background: var(--active-color);
            border-radius: 2px;
        }

        /* 全部分类固定按钮 */
        .all-cat-btn {
            padding: 12px 15px;
            font-size: 14px;
            color: #888;
            border-left: 1px solid #eee;
            background: linear-gradient(to right, rgba(255, 255, 255, 0), #fff 20%);
            cursor: pointer;
            display: flex;
            align-items: center;
        }

        /* 列表区域 */
        .list-section {
            padding: 10px 15px;
        }

        .list-title {
            font-size: 16px;
            font-weight: bold;
            padding-bottom: 8px;
            border-bottom: 2px solid var(--active-light);
            margin-bottom: 5px;
            color: #333;
        }

        .book-item {
            padding: 15px 0;
            border-bottom: 1px solid #f9f9f9;
            display: block;
            text-decoration: none;
            color: inherit;
        }

        .book-name {
            font-size: 16px;
            font-weight: bold;
            color: #333;
        }

        .book-item:active .book-name {
            color: var(--active-color);
        }

        .book-intro {
            font-size: 13px;
            color: #777;
            margin-top: 6px;
            line-height: 1.5;
            display: -webkit-box;
            -webkit-line-clamp: 2;
            -webkit-box-orient: vertical;
            overflow: hidden;
        }

        /* 强力推荐 */
        .text-only-row {
            padding: 10px 0;
            font-size: 14px;
            border-bottom: 1px solid #f9f9f9;
            display: flex;
            align-items: center;
        }

        .tag {
            color: var(--active-color);
            background: var(--active-light);
            padding: 2px 6px;
            border-radius: 3px;
            font-size: 11px;
            margin-right: 8px;
        }

        /* 侧边栏 */
        .side-mask {
            position: fixed;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background: rgba(0, 0, 0, 0.4);
            display: none;
            z-index: 100;
        }

        .side-menu {
            position: fixed;
            top: 0;
            right: -80%;
            width: 80%;
            height: 100%;
            background: #fff;
            z-index: 101;
            transition: 0.3s;
            overflow-y: auto;
        }

        .side-menu.active {
            right: 0;
        }

        .side-mask.active {
            display: block;
        }

        .side-head {
            padding: 15px;
            background: #f8f8f8;
            font-weight: bold;
            display: flex;
            justify-content: space-between;
            color: var(--active-color);
            border-bottom: 1px solid #eee;
        }

        .cat-group {
            padding: 10px 0;
        }

        .cat-l1 {
            padding: 10px 15px;
            background: #fcfcfc;
            font-size: 13px;
            color: #999;
            border-left: 3px solid var(--active-color);
            margin-bottom: 5px;
        }

        .cat-l2-list {
            display: flex;
            flex-wrap: wrap;
        }

        .cat-l2-item {
            width: 50%;
            padding: 15px;
            box-sizing: border-box;
            border-bottom: 1px solid #f0f0f0;
            border-right: 1px solid #f0f0f0;
            text-decoration: none;
            color: #444;
            font-size: 15px;
        }

        .cat-l2-item:active {
            background-color: var(--active-light);
            color: var(--active-color);
        }