/* 导航二级菜单（下拉）。电脑端鼠标悬停或键盘聚焦时展开；手机端在菜单里直接展开显示。 */
.nav-dropdown {
    position: relative;
    display: flex;
    align-self: stretch;
}

.nav-submenu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    z-index: 110;
    min-width: 240px;
    padding: 8px;
    background: var(--nav-bg, #ffffff);
    border: 1px solid var(--nav-border, #e2e8f0);
    border-radius: 14px;
    box-shadow: 0 12px 32px rgba(15, 23, 42, 0.12);
}

.nav-dropdown:hover .nav-submenu,
.nav-dropdown:focus-within .nav-submenu {
    display: block;
}

.nav-subitem {
    display: block;
    padding: 10px 14px;
    border-radius: 10px;
    color: var(--text-primary, #1e293b);
    font-size: 0.9rem;
    font-weight: 600;
    text-decoration: none;
    white-space: nowrap;
    transition: background 0.18s ease, color 0.18s ease;
}

.nav-subitem:hover,
.nav-subitem.active {
    background: #f1f5f9;
    color: #1d4ed8;
}

body.dark .nav-subitem:hover,
body.dark .nav-subitem.active {
    background: #1e293b;
    color: #60a5fa;
}

@media (max-width: 768px) {
    .nav-dropdown {
        flex-direction: column;
        align-self: auto;
        width: 100%;
    }

    .nav-submenu {
        display: block;
        position: static;
        min-width: 0;
        padding: 0 0 6px 60px;
        background: transparent;
        border: 0;
        box-shadow: none;
    }

    .nav-subitem {
        padding: 8px 12px;
        font-size: 0.85rem;
    }
}