/* ============================================
   Layout — 导航栏、页脚、网格布局
   ============================================ */

/* ---- 导航栏 ---- */
.site-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: var(--z-header);
    height: var(--header-height);
    display: flex;
    align-items: center;
    transition: all var(--transition-base);
}

.site-header.transparent {
    background: transparent;
}

.site-header.scrolled {
    background: rgba(10, 14, 26, 0.92);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    max-width: var(--container-wide);
    margin: 0 auto;
    padding: 0 var(--space-xl);
}

.header-logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    text-decoration: none;
}

.header-logo img {
    height: 32px;
    width: auto;
}

.header-logo-text {
    font-size: var(--text-xl);
    font-weight: var(--font-bold);
    color: var(--color-text-light);
    letter-spacing: -0.01em;
}

/* 主导航 */
.main-nav {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
}

.nav-item {
    position: relative;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 4px;
    padding: var(--space-sm) var(--space-md);
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    color: rgba(255, 255, 255, 0.75);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    cursor: pointer;
    text-decoration: none;
}

.nav-link:hover,
.nav-item.active .nav-link {
    color: #FFFFFF;
    background: rgba(255, 255, 255, 0.08);
}

.nav-link .chevron {
    width: 14px;
    height: 14px;
    transition: transform var(--transition-fast);
}

.nav-item.active .nav-link .chevron {
    transform: rotate(180deg);
}

/* 下拉菜单 */
.dropdown-menu {
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%) translateY(8px);
    min-width: 320px;
    background: rgba(17, 24, 39, 0.96);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-xl);
    padding: var(--space-md);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.4);
    z-index: 1000;
}

.nav-item.active .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateX(-50%) translateY(0);
}

.dropdown-group {
    padding: var(--space-sm) var(--space-md);
}

.dropdown-group-label {
    font-size: var(--text-xs);
    font-weight: var(--font-semibold);
    color: var(--color-text-light-3);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: var(--space-sm);
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-md);
    text-decoration: none;
    transition: background var(--transition-fast);
}

.dropdown-item:hover {
    background: rgba(255, 255, 255, 0.06);
}

.dropdown-item-icon {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-md);
    background: var(--gradient-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 16px;
    flex-shrink: 0;
}

.dropdown-item-text {
    flex: 1;
}

.dropdown-item-name {
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    color: var(--color-text-light);
}

.dropdown-item-desc {
    font-size: var(--text-xs);
    color: var(--color-text-light-3);
    margin-top: 1px;
}

.dropdown-divider {
    height: 1px;
    background: rgba(255, 255, 255, 0.06);
    margin: var(--space-sm) 0;
}

/* Header右侧 */
.header-actions {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

/* 汉堡菜单 */
.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: var(--space-sm);
    cursor: pointer;
}

.hamburger span {
    width: 22px;
    height: 2px;
    background: #FFFFFF;
    border-radius: 1px;
    transition: all var(--transition-base);
}

.hamburger.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.hamburger.active span:nth-child(2) {
    opacity: 0;
}

.hamburger.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
}

/* 移动端导航 */
.mobile-nav {
    display: none;
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(10, 14, 26, 0.98);
    backdrop-filter: blur(20px);
    padding: var(--space-xl);
    overflow-y: auto;
    z-index: var(--z-overlay);
}

.mobile-nav.open {
    display: block;
}

.mobile-nav-group {
    margin-bottom: var(--space-xl);
}

.mobile-nav-group-title {
    font-size: var(--text-xs);
    font-weight: var(--font-semibold);
    color: var(--color-text-light-3);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: var(--space-md);
}

.mobile-nav-link {
    display: block;
    padding: var(--space-md) 0;
    font-size: var(--text-lg);
    font-weight: var(--font-medium);
    color: var(--color-text-light);
    text-decoration: none;
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.mobile-nav-link:hover {
    color: var(--color-accent);
}

/* ---- 页脚 ---- */
.site-footer {
    background: var(--color-bg-dark);
    color: var(--color-text-light-2);
    padding: var(--space-4xl) 0 var(--space-2xl);
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr 1fr;
    gap: var(--space-3xl);
    margin-bottom: var(--space-3xl);
}

.footer-brand {
    max-width: 280px;
}

.footer-brand-logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    margin-bottom: var(--space-lg);
}

.footer-brand-logo img {
    height: 48px;
    max-width: 160px;
    object-fit: contain;
}

.footer-brand p {
    font-size: var(--text-sm);
    color: var(--color-text-light-3);
    line-height: var(--leading-relaxed);
}

.footer-col h4 {
    font-size: var(--text-sm);
    font-weight: var(--font-semibold);
    color: var(--color-text-light);
    margin-bottom: var(--space-lg);
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.footer-col ul {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.footer-col a {
    font-size: var(--text-sm);
    color: var(--color-text-light-3);
    transition: color var(--transition-fast);
}

.footer-col a:hover {
    color: var(--color-text-light);
}

.footer-bottom {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    padding-top: var(--space-2xl);
    border-top: 1px solid rgba(255, 255, 255, 0.06);
}

.footer-copyright {
    font-size: var(--text-sm);
    color: var(--color-text-light-3);
}

.footer-beian {
    flex-basis: 100%;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: var(--space-lg);
    margin-top: var(--space-sm);
    font-size: 12px;
    line-height: 1.6;
    color: var(--color-text-light-3);
}

.footer-beian a {
    color: inherit;
    text-decoration: none;
    transition: color var(--transition-base);
}

.footer-beian a:hover {
    color: var(--color-primary);
}

.footer-social {
    display: flex;
    gap: var(--space-md);
}

.footer-social a {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-md);
    background: rgba(255, 255, 255, 0.06);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--color-text-light-3);
    transition: all var(--transition-fast);
}

.footer-social a:hover {
    background: var(--color-primary);
    color: #FFFFFF;
}

/* ---- 通用Section ---- */
.section {
    padding: var(--space-5xl) 0;
}

.section-dark {
    background: var(--color-bg-dark);
}

.section-dark-2 {
    background: var(--color-bg-dark-2);
}

.section-light {
    background: var(--color-bg-light);
}

.section-light-2 {
    background: var(--color-bg-light-2);
}

/* 网格布局 */
.grid-2 {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-2xl);
}

.grid-3 {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-2xl);
}

.grid-4 {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-2xl);
}

.grid-auto {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--space-2xl);
}

/* 两列图文布局 */
.split-layout {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-3xl);
    align-items: center;
}

.split-layout.reverse {
    direction: rtl;
}

.split-layout.reverse > * {
    direction: ltr;
}

/* ---- 响应式 ---- */
@media (max-width: 1024px) {
    .footer-grid {
        grid-template-columns: 1fr 1fr;
        gap: var(--space-2xl);
    }

    .footer-brand {
        grid-column: 1 / -1;
        max-width: none;
    }

    .grid-4 {
        grid-template-columns: repeat(2, 1fr);
    }

    .split-layout {
        gap: var(--space-2xl);
    }
}

@media (max-width: 768px) {
    .main-nav,
    .header-actions .btn {
        display: none;
    }

    .hamburger {
        display: flex;
    }

    .section {
        padding: var(--space-3xl) 0;
    }

    .grid-2,
    .grid-3,
    .grid-4,
    .split-layout {
        grid-template-columns: 1fr;
    }

    .footer-grid {
        grid-template-columns: 1fr;
        gap: var(--space-xl);
    }

    .footer-bottom {
        flex-direction: column;
        gap: var(--space-md);
        text-align: center;
    }
}