/* ================= 核心变量定义 ================= */
        :root {
            --primary: #003366;      /* 工业深蓝：稳重、科技 */
            --primary-light: #004d99;
            --accent: #ff6600;       /* 安全橙：警示、行动 */
            --bg-body: #f4f7fa;      /* 浅灰背景 */
            --text-main: #333333;
            --text-light: #666666;
            --white: #ffffff;
            --border: #e0e0e0;
            --shadow: 0 4px 12px rgba(0,0,0,0.08);
        }

        /* ================= 基础重置 ================= */
        * { margin: 0; padding: 0; box-sizing: border-box; outline: none; }
        body { 
            font-family: 'Roboto', sans-serif; 
            background-color: var(--bg-body); 
            color: var(--text-main); 
            line-height: 1.6; 
            overflow-x: hidden; 
            display: flex;
            flex-direction: column;
            min-height: 100vh;
        }
        a { text-decoration: none; color: inherit; transition: 0.3s; }
        ul { list-style: none; }
        img { max-width: 100%; display: block; }

        /* ================= 布局系统 (宽屏满屏) ================= */
        .container-fluid {
            width: 100%;
            padding: 0 4%; /* 左右保留 4% 的呼吸空间 */
            margin: 0 auto;
            max-width: 1920px; /* 限制超大屏的最大宽度 */
        }
        
        /* 响应式断点控制 */
        @media (max-width: 768px) {
            .container-fluid { padding: 0 15px; }
        }

        /* ================= 顶部与导航 ================= */
        .top-bar {
            background: #f0f2f5;
            border-bottom: 1px solid var(--border);
            font-size: 13px;
            padding: 8px 0;
            color: var(--text-light);
        }
        .top-bar-flex { display: flex; justify-content: space-between; align-items: center; }

        header { background: var(--white); padding: 15px 0; box-shadow: var(--shadow); position: relative; z-index: 100; }
        .header-content { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 20px; }
        
        .logo { 
            font-family: 'Oswald', sans-serif; 
            font-size: 28px; 
            font-weight: 700; 
            color: var(--primary); 
            display: flex; 
            align-items: center; 
            gap: 12px; 
            cursor: pointer;
        }
        .logo i { color: var(--accent); font-size: 32px; }
        .logo-text div:last-child { font-size: 12px; color: var(--text-light); font-weight: 400; letter-spacing: 1px; font-family: 'Roboto'; }

        /* 导航菜单 */
        .nav-wrapper { background: var(--primary); color: var(--white); position: sticky; top: 0; z-index: 999; }
        .nav-list { display: flex; overflow-x: auto; }
        .nav-item { cursor: pointer; padding: 16px 25px; font-weight: 500; font-size: 15px; white-space: nowrap; transition: 0.3s; border-bottom: 3px solid transparent; }
        .nav-item:hover, .nav-item.active { background: var(--primary-light); border-bottom-color: var(--accent); }
        .mobile-menu-btn { display: none; color: white; font-size: 24px; cursor: pointer; padding: 15px; }

        /* ================= 通用组件 ================= */
        .btn { padding: 10px 25px; border-radius: 4px; cursor: pointer; font-weight: bold; border: none; transition: 0.3s; display: inline-flex; align-items: center; gap: 8px; }
        .btn-primary { background: var(--primary); color: white; }
        .btn-primary:hover { background: var(--primary-light); }
        .btn-accent { background: var(--accent); color: white; }
        .btn-accent:hover { background: #e65c00; }
        .btn-outline { background: transparent; border: 1px solid var(--primary); color: var(--primary); }
        .btn-outline:hover { background: var(--primary); color: white; }

        .section-header { 
            margin: 40px 0 25px; 
            border-left: 6px solid var(--primary); 
            padding-left: 15px; 
            font-family: 'Oswald'; 
            font-size: 26px; 
            color: var(--text-main);
            display: flex;
            justify-content: space-between;
            align-items: center;
        }
        .section-header span { font-size: 14px; color: var(--text-light); font-family: 'Roboto'; font-weight: normal; cursor: pointer; }

        /* ================= 页面特定样式 ================= */
        
        /* 首页 Hero */
        .hero-layout { display: grid; grid-template-columns: 1.2fr 1fr; gap: 30px; padding: 40px 0; }
        .hero-banner { 
            background: linear-gradient(135deg, rgba(0,51,102,0.9), rgba(0,30,60,0.8)), url('https://images.unsplash.com/photo-1581091226825-a6a2a5aee158?auto=format&fit=crop&w=1920&q=80');
            background-size: cover;
            background-position: center;
            border-radius: 8px;
            padding: 60px;
            color: white;
            display: flex;
            flex-direction: column;
            justify-content: center;
            box-shadow: var(--shadow);
        }
        
        /* 选型计算器 */
        .selection-panel { background: white; padding: 30px; border-radius: 8px; box-shadow: var(--shadow); border-top: 5px solid var(--accent); }
        .selection-title { font-family: 'Oswald'; font-size: 22px; margin-bottom: 20px; color: var(--primary); display: flex; align-items: center; gap: 10px; }
        .selection-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 15px; }
        .input-group label { font-size: 12px; font-weight: bold; color: var(--text-light); margin-bottom: 5px; display: block; }
        .input-group input, .input-group select { width: 100%; padding: 10px; border: 1px solid var(--border); border-radius: 4px; font-size: 14px; background: #f9f9f9; }
        .input-group input:focus { border-color: var(--primary); background: white; }

        /* 卡片网格 */
        .grid-cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 20px; }
        .card { background: white; border: 1px solid var(--border); transition: 0.3s; padding: 0; overflow: hidden; position: relative; }
        .card:hover { transform: translateY(-5px); box-shadow: var(--shadow); border-color: var(--accent); }
        .card-img { height: 180px; background: #f4f7fa; display: flex; align-items: center; justify-content: center; color: #cbd5e0; }
        .card-body { padding: 20px; }
        
        /* 表格样式 */
        .data-table { width: 100%; border-collapse: collapse; background: white; font-size: 14px; }
        .data-table th { background: var(--primary); color: white; padding: 15px; text-align: left; }
        .data-table td { padding: 15px; border-bottom: 1px solid var(--border); }
        .data-table tr:hover { background-color: #f9f9f9; }

        /* 论坛列表 */
        .forum-item { background: white; padding: 20px; border-bottom: 1px solid var(--border); display: flex; gap: 20px; align-items: flex-start; }
        .forum-stat { background: #f0f2f5; padding: 10px; border-radius: 4px; text-align: center; min-width: 60px; }
        
        /* 底部 */
        footer { background: #1a202c; color: #a0aec0; padding: 60px 0 20px; margin-top: auto; }
        .footer-cols { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 40px; margin-bottom: 40px; }
        .footer-title { color: white; font-family: 'Oswald'; font-size: 18px; margin-bottom: 20px; border-bottom: 1px solid #2d3748; padding-bottom: 10px; display: inline-block; }

        /* ================= 移动端适配 ================= */
        @media (max-width: 992px) {
            .hero-layout { grid-template-columns: 1fr; }
            .selection-grid { grid-template-columns: repeat(2, 1fr); }
        }
        @media (max-width: 768px) {
            .nav-list { display: none; flex-direction: column; position: absolute; top: 100%; left: 0; width: 100%; background: var(--primary); }
            .nav-list.show { display: flex; }
            .nav-item { width: 100%; border-bottom: 1px solid rgba(255,255,255,0.1); }
            .mobile-menu-btn { display: block; }
            .logo { font-size: 22px; }
            .selection-grid { grid-template-columns: 1fr; } /* 手机端单列 */
            .header-content { justify-content: center; text-align: center; }
        }