/* ===== css/nav.css - 全站统一导航样式（深蓝金商务版）===== */
:root {
    --navy: #0A1A2F;        /* 深蓝背景 */
    --gold: #B8860B;         /* 金色点缀 */
    --light-gold: #D4AF37;   /* 亮金悬停 */
    --white: #FFFFFF;
    --light-bg: #F5F7FA;
    --text-dark: #2c3e50;
    --text-light: #7f8c8d;
    --transition: all 0.25s ease;
}

/* 头部导航 */
header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    background-color: var(--navy);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
    border-bottom: 2px solid var(--gold);
}

.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 30px;
    height: 80px;
}

/* Logo */
.logo {
    display: flex;
    align-items: center;
    text-decoration: none;
    gap: 10px;
}

.brand-logo {
    height: 40px;
    width: auto;
    display: block;
}

.logo-cn {
    font-size: 26px;
    font-weight: 700;
    color: var(--white);
    letter-spacing: 2px;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

/* 桌面导航 */
nav ul {
    display: flex;
    list-style: none;
    gap: 32px;
    margin: 0;
    padding: 0;
}

nav ul li a {
    text-decoration: none;
    color: rgba(255, 255, 255, 0.9);
    font-weight: 500;
    font-size: 16px;
    padding: 8px 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    transition: var(--transition);
    position: relative;
    letter-spacing: 0.5px;
}

nav ul li a .nav-en {
    font-size: 11px;
    color: rgba(255, 255, 255, 0.6);
    font-weight: 400;
    margin-top: 2px;
    transition: var(--transition);
    text-transform: uppercase;
}

/* 悬停 & 激活状态 - 金色 */
nav ul li a:hover,
nav ul li a.active {
    color: var(--light-gold);
}

nav ul li a:hover .nav-en,
nav ul li a.active .nav-en {
    color: var(--light-gold);
}

/* 金色下划线 - 硬朗直线 */
nav ul li a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 3px;
    background-color: var(--gold);
    transition: var(--transition);
    border-radius: 0;
}

nav ul li a:hover::after,
nav ul li a.active::after {
    width: 100%;
}

/* 移动端汉堡菜单 */
.mobile-toggle {
    display: none;
    width: 44px;
    height: 44px;
    align-items: center;
    justify-content: center;
    font-size: 26px;
    color: var(--white);
    cursor: pointer;
    transition: var(--transition);
}

.mobile-toggle:hover {
    color: var(--gold);
}

/* ===== 移动端导航 (≤768px) ===== */
@media (max-width: 768px) {
    body {
        padding-top: 70px;
    }
    
    .header-container {
        height: 70px;
        padding: 0 20px;
    }

    .brand-logo {
        height: 34px;
    }

    .logo-cn {
        font-size: 22px;
    }

    .mobile-toggle {
        display: flex;
    }

    nav {
        position: fixed;
        top: 70px;
        left: 0;
        width: 100%;
        background-color: #0C1E33;
        padding: 20px;
        box-shadow: 0 10px 20px rgba(0, 0, 0, 0.3);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: transform 0.3s ease, opacity 0.3s ease, visibility 0.3s ease;
        border-top: 1px solid var(--gold);
        border-bottom: 2px solid var(--gold);
        max-height: calc(100vh - 70px);
        overflow-y: auto;
    }

    nav.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }

    nav ul {
        flex-direction: column;
        gap: 12px;
    }

    nav ul li a {
        padding: 14px 20px;
        font-size: 18px;
        background-color: rgba(255, 255, 255, 0.05);
        border-radius: 0;
        border-left: 3px solid transparent;
        align-items: flex-start;
        color: rgba(255, 255, 255, 0.9);
    }

    nav ul li a .nav-en {
        display: inline-block;
        margin-left: 8px;
        font-size: 12px;
    }

    nav ul li a.active {
        background-color: rgba(184, 134, 11, 0.15);
        border-left-color: var(--gold);
        color: var(--light-gold);
    }

    nav ul li a.active .nav-en {
        color: var(--light-gold);
    }

    nav ul li a::after {
        display: none;
    }
}

/* 超小屏 */
@media (max-width: 480px) {
    .brand-logo {
        height: 30px;
    }

    .logo-cn {
        font-size: 20px;
    }

    nav ul li a {
        font-size: 16px;
        padding: 12px 16px;
    }
}

/* 为固定导航留出body内边距 */
body {
    padding-top: 80px;
}

@media (max-width: 768px) {
    body {
        padding-top: 70px;
    }
}