* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', Tahoma, Geneva, sans-serif;
        }
        
        body {
            background: #f5f5f5;
            color: #333;
            line-height: 1.6;
            min-height: 100vh;
            padding-top: 70px;
        }
        
        /* 固定导航栏【原始配色完全保留，无修改】 */
        .navbar {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            background: rgba(255, 255, 255, 0.95);
            box-shadow: 0 2px 15px rgba(0, 0, 0, 0.1);
            z-index: 1000;
            padding: 0 20px;
        }
        
        .nav-container {
            max-width: 1200px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            height: 60px;
            position: relative;
        }
        
        .logo {
            font-size: 1.5rem;
            font-weight: bold;
            color: #4a6fcb;
            display: flex;
            align-items: center;
        }
        
        .logo i {
            margin-right: 10px;
            font-size: 1.8rem;
        }
        
        .nav-menu {
            display: flex;
            list-style: none;
        }
        
        .nav-item {
            margin-left: 30px;
            position: relative;
        }
        
        .nav-link {
            text-decoration: none;
            color: #333;
            font-weight: 600;
            padding: 10px 0;
            transition: color 0.3s;
            display: flex;
            align-items: center;
        }
        
        .nav-link i {
            margin-right: 8px;
            font-size: 1.1rem;
        }
        
        .nav-link:hover {
            color: #4a6fcb;
        }
        
        .nav-link.active {
            color: #4a6fcb;
            border-bottom: 2px solid #4a6fcb;
        }

        /* ========== 新增下拉二级菜单（不改动导航原有配色） ========== */
        .submenu {
            position: absolute;
            top: 100%;
            left: 0;
            min-width: 220px;
            background: #ffffff;
            box-shadow: 0 6px 18px rgba(0, 0, 0, 0.12);
            border-radius: 8px;
            overflow: hidden;
            opacity: 0;
            visibility: hidden;
            transform: translateY(10px);
            transition: all 0.25s ease;
            z-index: 999;
            list-style: none;
        }
        .nav-item:hover > .submenu {
            opacity: 1;
            visibility: visible;
            transform: translateY(0);
        }
        .submenu li {
            width: 100%;
        }
        .submenu-link {
            display: flex;
            align-items: center;
            gap: 8px;
            padding: 12px 18px;
            color: #333;
            text-decoration: none;
            font-weight: 500;
            transition: background 0.2s;
        }
        .submenu-link:hover {
            background: #f0f7ff;
            color: #4a6fcb;
        }
        .submenu-link i {
            width: 16px;
            text-align: center;
        }
        
        /* 汉堡菜单样式【原样保留】 */
        .hamburger {
            display: none;
            flex-direction: column;
            cursor: pointer;
            padding: 5px;
        }
        
        .hamburger span {
            width: 25px;
            height: 3px;
            background: #333;
            margin: 3px 0;
            transition: 0.3s;
            border-radius: 2px;
        }
        
        .hamburger.active span:nth-child(1) {
            transform: rotate(-45deg) translate(-5px, 6px);
        }
        
        .hamburger.active span:nth-child(2) {
            opacity: 0;
        }
        
        .hamburger.active span:nth-child(3) {
            transform: rotate(45deg) translate(-5px, -6px);
        }
        
        .container {
            max-width: 1000px;
            margin: 0 auto;
            padding: 20px;
            min-height: calc(100vh - 70px);
            display: flex;
            flex-direction: column;
        }
        
        header {
            text-align: center;
            padding: 30px 0;
            color: #333;
        }
        
        header h1 {
            font-size: 2.5rem;
            margin-bottom: 10px;
            color: #4a6fcb;
        }
        
        header p {
            font-size: 1.1rem;
            max-width: 600px;
            margin: 0 auto;
            color: #666;
        }
        
        .card {
            background: #ffffff;
            border-radius: 15px;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
            overflow: hidden;
            margin-bottom: 30px;
        }
        
        .form-section {
            padding: 30px;
            background: #ffffff;
        }

        /* 物料分类卡片布局 */
        .material-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
            gap: 24px;
            margin-top: 20px;
        }
        .material-card {
            border: 2px solid #e8edf8;
            border-radius: 12px;
            padding: 28px 20px;
            text-align: center;
            transition: all 0.3s ease;
            cursor: pointer;
            text-decoration: none;
            color: #333;
        }
        .material-card:hover {
            border-color: #4a6fcb;
            background: #f0f7ff;
            transform: translateY(-4px);
            box-shadow: 0 8px 20px rgba(74,111,203,0.12);
        }
        .material-card i {
            font-size: 3rem;
            color: #4a6fcb;
            margin-bottom: 16px;
        }
        .material-card h3 {
            font-size: 1.2rem;
            margin-bottom: 8px;
        }
        .material-card p {
            font-size: 0.9rem;
            color: #666;
        }
       
        footer {
            text-align: center;
            padding: 25px 0;
            color: #666;
            font-size: 1rem;
            margin-top: 20px;
        }
        
        @media (max-width: 768px) {
            .form-section {
                padding: 20px 15px;
            }
            .material-grid {
                grid-template-columns: 1fr 1fr;
                gap: 16px;
            }
            header h1 {
                font-size: 2rem;
            }
            /* 移动端导航【原始样式不变】 */
            .hamburger {
                display: flex;
            }
            .nav-menu {
                position: absolute;
                top: 100%;
                left: 0;
                width: 100%;
                background: rgba(255, 255, 255, 0.98);
                flex-direction: column;
                padding: 10px 0;
                box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
                transform: translateY(-10px);
                opacity: 0;
                visibility: hidden;
                transition: all 0.3s ease;
            }
            .nav-menu.active {
                transform: translateY(0);
                opacity: 1;
                visibility: visible;
            }
            .nav-item {
                margin: 10px 0;
                width: 100%;
                text-align: center;
            }
            .nav-link {
                justify-content: center;
                padding: 12px 20px;
            }
            /* 移动端下拉菜单适配 */
            .submenu {
                position: static;
                box-shadow: none;
                opacity: 1;
                visibility: visible;
                transform: none;
                background: #f7f9fc;
                width: 90%;
                margin: 8px auto 0;
                border-radius: 6px;
            }
            .submenu-link {
                justify-content: center;
            }
        }
        
        @media (max-width: 480px) {
            .material-grid {
                grid-template-columns: 1fr;
            }
            .nav-container {
                flex-direction: row;
                height: 60px;
                padding: 0;
            }
            .logo {
                margin-bottom: 0;
            }
            body {
                padding-top: 70px;
            }
        }