* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: "Microsoft YaHei", "思源黑体", sans-serif;
        }
        body {
            background-color: #f5f7fa;
            color: #2c3e50;
            line-height: 1.6;
        }
        .container {
            max-width: 1280px;
            margin: 0 auto;
            padding: 0 20px;
        }

 /* ========== 顶部导航 ========== */
        .site-header {
            width: 100%;
            background: #ffffff;
            box-shadow: 0 2px 8px rgba(0, 42, 90, 0.08);
            position: sticky;
            top: 0;
            z-index: 9999;
        }
        .nav-container {
            height: 66px;
            display: flex;
            align-items: center;
            justify-content: space-between;
        }
        .site-logo {
            font-size: 20px;
            font-weight: 700;
            color: #0052d9;
            letter-spacing: 1px;
            width:180px;
            height: 26px;
            background: url(../images/blue-logo.png) no-repeat center;
            background-size: 100% 100%;
        }
        .nav-list {
            display: flex;
            list-style: none;
            height: 100%;
        }
        .nav-list > li {
            position: relative;
            height: 66px;
            padding: 0 22px;
            line-height: 66px;
            cursor: pointer;
            transition: background 0.2s ease;
        }
        .nav-list > li > a {
            display: block;
            color: #2c3e50;
            text-decoration: none;
            font-size: 16px;
            font-weight: 500;
        }
        .nav-list > li:hover, .nav-list > li.active {
            background: #f0f6ff;
        }
        .nav-list > li:hover > a, .nav-list > li.active > a {
            color: #0052d9;
        }
        .nav-list > li:hover {
            background: #f0f6ff;
        }
        .nav-list > li:hover > a {
            color: #0052d9;
        }
        .sub-menu {
            position: absolute;
            top: 100%;
            left: 0;
            min-width: 210px;
            background: #ffffff;
            box-shadow: 0 6px 16px rgba(0, 42, 90, 0.12);
            list-style: none;
            display: none;
            padding: 8px 0;
            border-radius: 0 0 4px 4px;
        }
        .sub-menu li {
            position: relative;
            line-height: 44px;
            padding: 0 22px;
            transition: background 0.2s ease;
        }
        .sub-menu li a {
            display: block;
            color: #4a5a6b;
            text-decoration: none;
            font-size: 15px;
        }
        .sub-menu li:hover {
            background: #f0f6ff;
        }
        .sub-menu li:hover > a {
            color: #0052d9;
        }
        .third-menu {
            position: absolute;
            top: 0;
            left: 100%;
            min-width: 190px;
            background: #ffffff;
            box-shadow: 0 6px 16px rgba(0, 42, 90, 0.12);
            list-style: none;
            display: none;
            padding: 8px 0;
            border-radius: 0 4px 4px 0;
        }
        .nav-list > li:hover > .sub-menu {
            display: block;
        }
        .sub-menu li:hover > .third-menu {
            display: block;
        }
        .has-sub > a::after {
            content: "▾";
            margin-left: 6px;
            font-size: 12px;
            color: #94a3b8;
        }
        .has-third > a::after {
            content: "▸";
            float: right;
            font-size: 12px;
            color: #94a3b8;
            margin-top: 1px;
        }
        .nav-cta {
            background: #0052d9;
            color: #fff !important;
            padding: 8px 18px;
            border-radius: 4px;
            line-height: normal;
        }
        .nav-cta:hover {
            background: #0041b0;
        }
/* ========== 页脚 ========== */
        .site-footer {
            background: #0f1d30;
            color: #94a3b8;
            padding: 60px 0 30px;
        }
        .footer-grid {
            display: grid;
            grid-template-columns: 2fr 1fr 1fr 1fr;
            gap: 40px;
            margin-bottom: 40px;
        }
        .footer-logo {
            font-size: 22px;
            font-weight: 700;
            color: #fff;
            margin-bottom: 16px;
        }
        .footer-desc {
            font-size: 14px;
            line-height: 1.8;
            margin-bottom: 20px;
        }
        .footer-col h4 {
            color: #fff;
            font-size: 16px;
            margin-bottom: 20px;
            font-weight: 500;
        }
        .footer-col ul {
            list-style: none;
        }
        .footer-col ul li {
            margin-bottom: 10px;
        }
        .footer-col ul li a {
            color: #94a3b8;
            text-decoration: none;
            font-size: 14px;
            transition: color 0.2s ease;
        }
        .footer-col ul li a:hover {
            color: #fff;
        }
        .footer-contact li {
            font-size: 14px;
            margin-bottom: 12px;
            line-height: 1.7;
        }
        .footer-copyright {
            border-top: 1px solid #1e2f45;
            padding-top: 24px;
            text-align: center;
            font-size: 13px;
            color: #64748b;
        }

        /* 回到顶部 */
        .back-top {
            position: fixed;
            bottom: 40px;
            right: 30px;
            width: 44px;
            height: 44px;
            background: #0052d9;
            color: #fff;
            border-radius: 4px;
            display: flex;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            box-shadow: 0 4px 12px rgba(0, 82, 217, 0.3);
        }