.site-header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: var(--nav-height);
    background: rgba(253, 253, 253, 0.95); 
    backdrop-filter: blur(10px); 
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 5%;
    z-index: 1000;
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
    box-sizing: border-box;
    transition: var(--transition);
}

/* --- 2. Logo 样式 --- */
.site-logo a {
    font-size: 36px;
    font-weight: 700;
    color: var(--sino-gold);
    text-decoration: none;
    display: flex;
    align-items: baseline;
}

.site-logo small {
    font-size: 18px;
    color: var(--sino-black);
    font-weight: 400;
    margin-left: 2px;
}

/* --- 3. 导航菜单 --- */
.main-navigation ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    gap: 40px;
    align-items: center;
}

.nav-item {
    position: relative;
}

.nav-link {
    text-decoration: none;
    color: var(--sino-black);
    font-family: sans-serif;
    font-size: 14px;
    transition: var(--transition);
    padding: 10px 0;
    position: relative;
}

/* 导航悬停特效：金色下划线自中间向两边展开 */
.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 1.5px;
    background-color: var(--sino-gold);
    transition: var(--transition);
    transform: translateX(-50%);
}

.nav-link:hover {
    color: var(--sino-gold);
}

.nav-link:hover::after {
    width: 100%;
}

/* --- 4. Selection 购物车数字角标 --- */
.badge {
    position: absolute;
    top: -8px;
    right: -18px;
    background-color: var(--sino-gold);
    color: #fff;
    font-size: 9px;
    min-width: 16px;
    height: 16px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-family: sans-serif;
    font-weight: 700;
    box-shadow: 0 2px 5px rgba(197, 160, 89, 0.4);
    pointer-events: none;
}

/* --- 5. 响应式处理 --- */
@media (max-width: 768px) {
    .site-header {
        height: 70px;
        padding: 0 20px;
    }
    
    .site-logo a {
        font-size: 18px;
    }

    .main-navigation ul {
        gap: 20px;
    }

    .nav-link {
        font-size: 10px;
        letter-spacing: 1px;
    }
}