/**
 * 头部导航栏样式
 * 
 * 包含顶部导航栏、Logo、菜单和用户操作的样式
 */

/* ========== 头部容器 ========== */
.site-header {
    background: white;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
    height: 70px;
}

.site-header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
}

/* ========== Logo ========== */
.logo a {
    display: flex;
    align-items: center;
    text-decoration: none;
}

.logo-text {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    letter-spacing: 2px;
}

/* ========== 主导航 ========== */
/* 导航整体靠右，向右侧的登录/注册按钮靠近 */
.main-nav {
    margin-left: auto;
    margin-right: 40px;
}

.main-nav ul {
    display: flex;
    list-style: none;
    gap: var(--spacing-xl);
}

.main-nav > ul > li {
    position: relative;
}

.main-nav a {
    color: var(--text-primary);
    font-weight: 500;
    padding: var(--spacing-sm) 0;
    display: block;
    transition: color var(--transition-fast);
}

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

/* 下拉菜单 */
.main-nav .dropdown {
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    background: white;
    box-shadow: var(--shadow-lg);
    border-radius: var(--radius-md);
    min-width: 180px;
    padding: var(--spacing-sm) 0;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-fast);
    z-index: 100;
}

.main-nav li:hover .dropdown {
    opacity: 1;
    visibility: visible;
}

.main-nav .dropdown a {
    display: block;
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-primary);
}

.main-nav .dropdown a:hover {
    background-color: var(--bg-light);
    color: var(--primary-color);
}

/* ========== 用户操作 ========== */
.user-actions {
    display: flex;
    gap: var(--spacing-md);
    align-items: center;
}

.btn-login,
.btn-register {
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    font-weight: 500;
    transition: all var(--transition-fast);
}

.btn-login {
    color: var(--text-primary);
}

.btn-login:hover {
    color: var(--primary-color);
    background-color: var(--bg-light);
}

.btn-register {
    background-color: var(--primary-color);
    color: white;
}

.btn-register:hover {
    background-color: var(--primary-dark);
    color: white;
}

/* ========== 移动端响应式 ========== */
@media (max-width: 768px) {
    .site-header {
        height: auto;
        padding: var(--spacing-md) 0;
    }
    
    .site-header .container {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .main-nav {
        margin-left: 0;
        margin-right: 0;
    }

    .main-nav ul {
        flex-direction: column;
        gap: var(--spacing-md);
        align-items: center;
    }
    
    .main-nav .dropdown {
        position: static;
        transform: none;
        box-shadow: none;
        background: transparent;
        padding-left: var(--spacing-md);
    }
    
    .user-actions {
        justify-content: center;
    }
}