/* =========================================================
   导航栏 — 固定顶部、LOGO 居左+菜单居中+操作区居右
   ========================================================= */

.site-nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height);
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: saturate(180%) blur(14px);
    -webkit-backdrop-filter: saturate(180%) blur(14px);
    border-bottom: 1px solid transparent;
    z-index: var(--z-nav);
    transition: height var(--transition),
                background var(--transition),
                border-color var(--transition),
                box-shadow var(--transition);
}

/* 滚动后的状态：更紧凑、增加分割线 */
.site-nav.is-scrolled {
    height: var(--nav-height-scrolled);
    background: rgba(255, 255, 255, 0.97);
    border-bottom-color: var(--color-border);
    box-shadow: var(--shadow-sm);
}

.site-nav__inner {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--container-padding);
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-4);
}

/* ---------- Logo（独立元素，居左）---------- */
.site-nav__logo {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    flex-shrink: 0;
    font-family: var(--font-serif);
    font-weight: var(--weight-bold);
    font-size: 26px;
    color: var(--color-primary);
    letter-spacing: -0.02em;
    text-decoration: none;
    white-space: nowrap;
    padding: 0 var(--space-4);
    height: var(--nav-height);
    transform: translateY(-14px); /* LOGO上移，底部与菜单项文字中间对齐 */
    transition: height var(--transition);
}
.site-nav.is-scrolled .site-nav__logo {
    height: var(--nav-height-scrolled);
}
.site-nav__logo-mark {
    width: 42px;
    height: 42px;
    border-radius: 12px;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-secondary) 100%);
    display: grid;
    place-items: center;
    color: #fff;
    font-family: var(--font-serif);
    font-weight: var(--weight-bold);
    font-size: 19px;
    box-shadow: var(--shadow-sm);
}

/* ---------- 菜单（居中）---------- */
.site-nav__menu {
    display: flex;
    align-items: center;
    gap: var(--space-1);
    flex: 1 1 auto;
    justify-content: center;
    flex-wrap: nowrap;
    list-style: none;
    min-width: 0;
    overflow: visible;
}

.site-nav__item {
    position: relative;
}

.site-nav__link {
    display: inline-flex;
    align-items: center;
    height: var(--nav-height);
    padding: 0 var(--space-2);
    font-size: var(--font-size-small);
    font-weight: var(--weight-medium);
    color: var(--color-text);
    letter-spacing: 0.01em;
    white-space: nowrap;
    transition: color var(--transition-fast), height var(--transition);
    position: relative;
}
.site-nav.is-scrolled .site-nav__link {
    height: var(--nav-height-scrolled);
}
.site-nav__link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: var(--space-2);
    right: var(--space-2);
    height: 2px;
    background: var(--color-primary);
    transform: scaleX(0);
    transform-origin: left;
    transition: transform var(--transition);
    border-radius: 2px 2px 0 0;
}
.site-nav__link:hover,
.site-nav__item.is-active .site-nav__link {
    color: var(--color-primary);
}
.site-nav__link:hover::after,
.site-nav__item.is-active .site-nav__link::after {
    transform: scaleX(1);
}

/* 下拉子菜单 */
.site-nav__dropdown {
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%) translateY(8px);
    min-width: 240px;
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-pop);
    padding: var(--space-3);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition);
    list-style: none;
}
.site-nav__item:hover .site-nav__dropdown {
    opacity: 1;
    visibility: visible;
    transform: translateX(-50%) translateY(0);
}
.site-nav__dropdown a {
    display: block;
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius);
    font-size: var(--font-size-small);
    color: var(--color-text-body);
    transition: all var(--transition-fast);
}
.site-nav__dropdown a:hover {
    background: var(--color-primary-light);
    color: var(--color-primary);
}

/* ---------- 右侧功能区 ---------- */
.site-nav__actions {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    flex-shrink: 0;
    justify-content: flex-end;
}

/* 搜索框 */
.site-nav__search {
    position: relative;
    display: flex;
    align-items: center;
}
.site-nav__search-input {
    width: 90px;
    height: 40px;
    padding: 0 var(--space-3) 0 36px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-full);
    background: var(--color-bg-soft);
    font-size: var(--font-size-small);
    color: var(--color-text);
    outline: none;
    transition: all var(--transition-fast);
}
.site-nav__search-input::placeholder {
    color: var(--color-text-muted);
}
.site-nav__search-input:focus {
    border-color: var(--color-secondary);
    background: #fff;
    width: 120px;
    box-shadow: 0 0 0 4px rgba(30, 111, 217, 0.08);
}
.site-nav__search-icon {
    position: absolute;
    left: 14px;
    top: 50%;
    transform: translateY(-50%);
    width: 16px;
    height: 16px;
    color: var(--color-text-muted);
    pointer-events: none;
}

/* 语言切换 */
.site-nav__lang {
    display: inline-flex;
    align-items: center;
    gap: var(--space-1);
    height: 40px;
    padding: 0 var(--space-3);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-full);
    font-size: var(--font-size-small);
    color: var(--color-text);
    transition: all var(--transition-fast);
}
.site-nav__lang:hover {
    border-color: var(--color-primary);
    color: var(--color-primary);
}

/* 移动端汉堡按钮 */
.site-nav__toggle {
    display: none;
    width: 40px;
    height: 40px;
    border-radius: var(--radius);
    align-items: center;
    justify-content: center;
    color: var(--color-text);
}
.site-nav__toggle:hover { background: var(--color-bg-soft); }

/* ---------- 为固定导航给 body 让出空间 ---------- */
body { padding-top: var(--nav-height); }

/* =========================================================
   导航响应式
   ========================================================= */
@media (max-width: 1024px) {
    .site-nav__search-input { width: 70px; }
    .site-nav__search-input:focus { width: 90px; }
    .site-nav__link { padding: 0 var(--space-2); font-size: 13px; }
    .site-nav__menu { gap: 0; }
    .site-nav__inner { gap: var(--space-2); }
}

@media (max-width: 768px) {
    .site-nav__toggle { display: inline-flex; }
    .site-nav__menu {
        position: fixed;
        top: var(--nav-height);
        left: 0; right: 0;
        flex-direction: column;
        align-items: stretch;
        justify-content: flex-start;
        background: #fff;
        border-bottom: 1px solid var(--color-border);
        padding: var(--space-4) var(--space-6);
        gap: 0;
        transform: translateY(-10px);
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition);
        box-shadow: var(--shadow);
    }
    .site-nav.is-open .site-nav__menu {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }
    .site-nav__link {
        height: 48px !important;
        border-bottom: 1px solid var(--color-border);
    }
    .site-nav__link::after { display: none; }
    .site-nav__search,
    .site-nav__lang { display: none; }
}