/* ============================================
   布局:导航栏 / 页脚 / 栅格
   ============================================ */

/* ── 顶部全局导航(固定) ── */
.global-nav {
    position: fixed;
    top: 0; left: 0; right: 0;
    height: var(--nav-height);
    background: rgba(15, 23, 42, 0.85);
    backdrop-filter: saturate(180%) blur(12px);
    -webkit-backdrop-filter: saturate(180%) blur(12px);
    border-bottom: 1px solid var(--color-border);
    z-index: 1000;
    display: flex;
    align-items: center;
}
.global-nav .nav-inner {
    max-width: 100%;
    margin: 0;
    padding: 0 var(--space-lg);
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-md);
}
/* 中间菜单绝对居中(不被 logo/用户区宽度影响) */
.global-nav .nav-menu {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
}

/* Logo + 品牌名 */
.nav-brand {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    color: var(--color-text);
    font-weight: 700;
    font-size: 16px;
}
.nav-brand:hover { color: var(--color-text); }
.nav-brand img.brand-logo {
    width: 32px; height: 32px;
    border-radius: var(--radius-full);
    border: 2px solid var(--color-accent);
    object-fit: cover;
    box-shadow: 0 0 12px rgba(6, 182, 212, 0.4);
}
.nav-brand .brand-name {
    letter-spacing: 0.5px;
    background: var(--gradient-brand);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

/* 课程下拉 */
.nav-menu {
    display: flex;
    align-items: center;
    gap: var(--space-lg);
}
.nav-link {
    color: var(--color-text-secondary);
    font-size: 14px;
    font-weight: 500;
    padding: var(--space-sm) 0;
    position: relative;
    cursor: pointer;
}
.nav-link:hover { color: var(--color-accent); }

/* 课程下拉菜单 */
.nav-dropdown { position: relative; }
.nav-dropdown .dropdown-toggle::after {
    content: '▾';
    margin-left: 4px;
    font-size: 10px;
}
.dropdown-menu {
    position: absolute;
    top: calc(100% + 8px);
    left: 50%;
    transform: translateX(-50%);
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    min-width: 280px;
    padding: var(--space-sm);
    display: none;
    flex-direction: column;
    gap: 2px;
}
.nav-dropdown:hover .dropdown-menu,
.nav-dropdown.open .dropdown-menu { display: flex; }
.dropdown-item {
    display: block;
    padding: var(--space-sm) var(--space-md);
    color: var(--color-text-secondary);
    border-radius: var(--radius-sm);
    font-size: 13px;
    transition: all var(--transition-fast);
}
.dropdown-item:hover {
    background: var(--color-bg-surface);
    color: var(--color-accent);
}

/* 用户区 */
.nav-user {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}
.btn-login {
    background: var(--gradient-brand);
    color: #fff;
    padding: 8px 20px;
    border-radius: var(--radius-full);
    font-size: 13px;
    font-weight: 600;
    transition: all var(--transition-fast);
}
.btn-login:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-brand);
    color: #fff;
}

/* 右上角用户下拉菜单 */
.user-dropdown-wrap { position: relative; }
.user-trigger {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    padding: 2px;
    border-radius: 50%;
    cursor: pointer;
    transition: background var(--transition-fast), border-color var(--transition-fast), transform var(--transition-fast);
    border: 1px solid transparent;
    background: transparent;
}
.user-trigger:hover {
    background: var(--color-bg-surface);
    border-color: var(--color-border);
    transform: translateY(-1px);
}
.user-trigger:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}
.user-trigger-avatar {
    display: block;
    width: 34px;
    height: 34px;
    border-radius: 50%;
    object-fit: cover;
}

/* 用户下拉面板 */
.user-dropdown {
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    min-width: 248px;
    max-width: calc(100vw - 24px);
    padding: var(--space-sm);
    display: none;
    flex-direction: column;
    gap: 2px;
    z-index: 1100;
}
.user-dropdown.open { display: flex; }
.user-dropdown-header {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-md);
    border-bottom: 1px solid var(--color-border);
    margin-bottom: var(--space-xs);
}
.user-dropdown-name {
    color: var(--color-text);
    font-size: 14px;
    font-weight: 600;
}
.user-dropdown-sub {
    color: var(--color-text-muted);
    font-size: 12px;
}
.user-account-meta {
    display: grid;
    gap: var(--space-xs);
    padding: var(--space-sm) var(--space-md) var(--space-md);
    border-bottom: 1px solid var(--color-border);
    margin-bottom: var(--space-xs);
}
.user-account-meta > div {
    display: grid;
    grid-template-columns: 52px minmax(0, 1fr);
    align-items: baseline;
    gap: var(--space-sm);
}
.user-account-meta span {
    color: var(--color-text-muted);
    font-size: 12px;
}
.user-account-meta strong {
    min-width: 0;
    overflow: hidden;
    color: var(--color-text-secondary);
    font-size: 12px;
    font-weight: 500;
    text-align: right;
    text-overflow: ellipsis;
    white-space: nowrap;
}
.user-dropdown-item {
    display: block;
    width: 100%;
    padding: var(--space-sm) var(--space-md);
    border: 0;
    background: transparent;
    color: var(--color-text-secondary);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-family: inherit;
    font-size: 13px;
    text-align: left;
    transition: all var(--transition-fast);
}
.user-dropdown-item:hover {
    background: var(--color-bg-surface);
    color: var(--color-accent);
}
.user-dropdown-logout:hover {
    color: #f87171 !important;
    background: rgba(248, 113, 113, 0.1) !important;
}

/* 点击外部关闭下拉菜单 */
body:has(.user-dropdown.open) { cursor: default; }

/* ── 移动端汉堡 ── */
.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    cursor: pointer;
    padding: var(--space-sm);
}
.nav-toggle span {
    width: 22px; height: 2px;
    background: var(--color-text);
    transition: var(--transition-fast);
}

/* ── 页脚 ── */
.global-footer {
    background: var(--color-bg-elevated);
    border-top: 1px solid var(--color-border);
    padding: var(--space-2xl) var(--space-lg) var(--space-lg);
    margin-top: var(--space-3xl);
}
.footer-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: var(--space-2xl);
    margin-bottom: var(--space-xl);
}
.footer-brand {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}
.footer-brand img {
    width: 56px; height: 56px;
    border-radius: var(--radius-md);
}
.footer-brand-text { display: flex; flex-direction: column; gap: 4px; }
.footer-brand-name {
    font-size: 18px;
    font-weight: 900;
    letter-spacing: -0.5px;
    background: var(--gradient-brand);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}
.footer-brand-sub {
    font-size: 11px;
    color: var(--color-text-muted);
    letter-spacing: 2px;
    font-weight: 600;
}
.footer-brand p {
    color: var(--color-text-muted);
    font-size: 13px;
    line-height: 1.7;
    max-width: 320px;
}
.footer-col h4 {
    color: var(--color-text);
    font-size: 14px;
    font-weight: 600;
    margin-bottom: var(--space-md);
}
.footer-col ul { list-style: none; padding: 0; }
.footer-col li { margin-bottom: var(--space-sm); }
.footer-col a {
    color: var(--color-text-muted);
    font-size: 13px;
}
.footer-col a:hover { color: var(--color-accent); }
.footer-bottom {
    max-width: var(--max-width);
    margin: 0 auto;
    padding-top: var(--space-lg);
    border-top: 1px solid var(--color-border);
    text-align: center;
    color: var(--color-text-muted);
    font-size: 12px;
}

/* ── 响应式 ── */
@media (max-width: 768px) {
    .nav-menu, .nav-user .btn-login { display: none; }
    .nav-toggle { display: flex; }
    .nav-menu.mobile-open {
        display: flex;
        position: absolute;
        top: var(--nav-height);
        left: 0; right: 0;
        transform: none;
        background: var(--color-bg-elevated);
        flex-direction: column;
        padding: var(--space-md);
        border-bottom: 1px solid var(--color-border);
    }
    .footer-inner { grid-template-columns: 1fr; gap: var(--space-lg); }
}

/* 占位:防止内容被固定导航遮挡 */
.nav-placeholder { height: var(--nav-height); }