/* 顶部导航样式 */
.nav-link {
    color: rgba(255,255,255,0.8);
    font-weight: 500;
    transition: all 0.3s;
}

.nav-link:hover, .nav-link.active {
    color: #ffffff;
}

.navbar.fixed-top {
    background: linear-gradient(90deg, #ef7928, #fb6c3a);
}

.navbar .sub-menu {
    position: absolute;
    top: 100%;
    left: 0;
    background: rgba(0,0,0,0.85);
    border-radius: 6px;
    padding: 8px 0;
    min-width: 140px;
    opacity: 0;
    visibility: hidden;
    transform: translateY(8px);
    transition: opacity 0.25s ease, transform 0.25s ease, visibility 0.25s ease;
    will-change: opacity, transform, visibility;
    z-index: 1000;
}

.navbar .sub-menu a {
    display: block;
    padding: 8px 16px;
    color: #fff;
    text-decoration: none;
    white-space: nowrap;
    transition: background-color 0.2s ease, color 0.2s ease;
}

.navbar .sub-menu a:hover { background: rgba(255,255,255,0.1); }

.navbar .nav-item.position-relative:hover .sub-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

/* 移动端：禁用 hover 展开，改为点击展开 */
@media (max-width: 991.98px) {
    .navbar .sub-menu {
        position: static;
        background: transparent;
        border-radius: 0;
        padding: 0;
        margin-top: 0;
        min-width: auto;
        opacity: 0;
        visibility: hidden;
        
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.35s ease, opacity 0.25s ease, visibility 0.25s ease;
        will-change: max-height, opacity, visibility;
    }

    .navbar .nav-item.position-relative:hover .sub-menu {
        opacity: 0;
        visibility: hidden;
        
        max-height: 0;
        overflow: hidden;
    }

    .navbar .nav-item.position-relative.show-submenu .sub-menu {
        opacity: 1;
        visibility: visible;
        max-height: 320px;
        overflow: visible;
        
    }

    .navbar .sub-menu a {
        padding: 10px 0;
        color: #fff;
    }

    /* 移动端：下拉项不高亮 */
    .navbar .sub-menu a:hover {
        background: transparent;
    }

    .navbar .nav-item.position-relative.show-submenu .dropdown-toggle .caret-icon {
        transform: rotate(180deg);
    }
}