/* 底部导航 */
        .bottom-nav {
            position: fixed;
            bottom: 0;
            left: 0;
            width: 100%;
            background-color: white;
            padding: 12px 20px;
            display: flex;
            justify-content: space-around;
            align-items: center;
            box-shadow: 0 -4px 20px rgba(0, 0, 0, 0.08);
            z-index: 100;
            border-top: 1px solid #f0f0f0;
        }
        
        .nav-item {
            display: flex;
            flex-direction: column;
            align-items: center;
            text-decoration: none;
            color: #999;
            transition: all 0.3s ease;
            padding: 5px 10px;
            border-radius: 10px;
            position: relative;
        }
        
        .nav-item.active {
            color: #2a5bd7;
        }
        
        .nav-item:active {
            background-color: #f0f7ff;
        }
        
        .nav-icon {
            font-size: 20px;
            margin-bottom: 4px;
        }
        
        .nav-text {
            font-size: 11px;
            font-weight: 600;
        }
        
        .nav-item.active .nav-icon {
            color: #2a5bd7;
        }
        
        /* 二级菜单 */
        .submenu-overlay {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, 0.5);
            z-index: 1000;
            display: none;
            opacity: 0;
            transition: opacity 0.3s ease;
        }
        
        .submenu-overlay.active {
            display: block;
            opacity: 1;
        }
        
        .submenu-container {
            position: fixed;
            bottom: 0;
            left: 0;
            width: 100%;
            background-color: white;
            border-radius: 24px 24px 0 0;
            padding: 20px;
            z-index: 1001;
            transform: translateY(100%);
            transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
            box-shadow: 0 -10px 40px rgba(0, 0, 0, 0.15);
        }
        
        .submenu-container.active {
            transform: translateY(0);
        }
        
        .submenu-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 20px;
            padding-bottom: 15px;
            border-bottom: 1px solid #f0f0f0;
        }
        
        .submenu-title {
            font-size: 18px;
            font-weight: 700;
            color: #1a3a8f;
            display: flex;
            align-items: center;
            gap: 8px;
        }
        
        .submenu-close {
            width: 36px;
            height: 36px;
            border-radius: 50%;
            background-color: #f0f7ff;
            display: flex;
            align-items: center;
            justify-content: center;
            color: #2a5bd7;
            font-size: 16px;
            border: none;
            cursor: pointer;
        }
        
        .submenu-grid {
            display: grid;
            grid-template-columns: repeat(2, 1fr);
            gap: 15px;
        }
        
        .submenu-item {
            background-color: white;
            border-radius: 16px;
            padding: 18px;
            box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
            transition: all 0.3s ease;
            display: flex;
            flex-direction: column;
            align-items: center;
            text-align: center;
            border: 1px solid #eef5ff;
            text-decoration: none;
            color: inherit;
        }
        
        .submenu-item:active {
            transform: scale(0.96);
            box-shadow: 0 2px 8px rgba(0, 0, 0, 0.12);
        }
        
        .submenu-icon {
            width: 48px;
            height: 48px;
            border-radius: 12px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 20px;
            margin-bottom: 12px;
            color: white;
        }
        
        .submenu-item-title {
            font-size: 15px;
            font-weight: 700;
            color: #1a3a8f;
            margin-bottom: 6px;
        }
        
        .submenu-item-desc {
            font-size: 12px;
            color: #666;
        }