/* 头部导航栏样式 */

header {
    background: #ffffff;
    color: var(--primary-dark);
    padding: 0.85rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 1px 0 var(--border-light), 0 4px 16px rgba(13, 31, 60, 0.06);
}

header.scrolled {
    box-shadow: 0 1px 0 var(--border-light), 0 6px 24px rgba(13, 31, 60, 0.1);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.4rem;
    font-weight: 800;
    letter-spacing: -0.5px;
    color: var(--primary-dark);
    line-height: 1;
    text-decoration: none;
}

.logo-cn {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--accent-color);
    margin-top: 0.25rem;
    letter-spacing: 0.04em;
    text-transform: uppercase;
}

nav {
    display: flex;
    gap: 2.5rem;
    list-style: none;
}

nav a {
    color: var(--text-main);
    text-decoration: none;
    transition: color 0.2s;
    font-size: 0.9rem;
    font-weight: 500;
    letter-spacing: 0.01em;
    position: relative;
}

nav a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--primary-main);
    transform: scaleX(0);
    transition: transform 0.2s ease;
    border-radius: 1px;
}

nav a:hover {
    color: var(--primary-main);
}

nav a:hover::after {
    transform: scaleX(1);
}

.mobile-menu-toggle {
    display: none;
    background: transparent;
    color: var(--primary-dark);
    font-size: 1.5rem;
    border: none;
    cursor: pointer;
}

@media (max-width: 768px) {
    nav {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        flex-direction: column;
        gap: 0;
        background: #ffffff;
        padding: 0.5rem 0 1rem;
        border-top: 1px solid var(--border-light);
        box-shadow: 0 8px 24px rgba(13, 31, 60, 0.1);
    }

    nav.active {
        display: flex;
    }

    nav a {
        padding: 0.8rem 1.5rem;
        border-bottom: 1px solid var(--border-light);
    }

    nav a::after {
        display: none;
    }

    .mobile-menu-toggle {
        display: block;
    }
}