/* ============================================
   导航栏样式
   ============================================ */

header {
    position: fixed;
    top: 0;
    width: 100%;
    padding: 30px 50px;
    box-sizing: border-box;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: #000000;
    z-index: 100;
}

.logo {
    font-size: 3.0rem;
    font-weight: 900;
    text-decoration: none;
    color: var(--text-color);
    letter-spacing: -1px;
    white-space: nowrap;
}

nav {
    display: flex;
    gap: 0;
}

nav a {
    color: var(--text-color);
    text-decoration: none;
    margin-left: 30px;
    font-size: 1.6rem; /* 再放大一些，改善可见性 */
    text-transform: uppercase;
    transition: color 0.18s cubic-bezier(.2,.8,.2,1), transform 0.12s ease;
    will-change: transform, color;
    padding: 6px 4px;
    border-radius: 4px;
}

nav a:hover, nav a:focus {
    color: var(--accent-color);
    transform: translateY(-4px) scale(1.02); /* 更明显的悬停反馈 */
}

nav a:active {
    transform: scale(0.985);
}

nav a:focus {
    outline: 2px solid rgba(136,136,136,0.12);
    outline-offset: 4px;
}

/* 下拉菜单 */
.dropdown {
    display: inline-flex;
    align-items: center; /* 与其他 nav 项垂直居中 */
    position: relative;
}

/* 扩大 dropdown 的悬停区域，包括菜单下方 */
.dropdown::after {
    content: '';
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    height: 12px; /* 扩大触发器和菜单之间的区域 */
    pointer-events: auto;
}


.dropdown-content {
    /* 下拉位置调整，使用透明度与浮动阴影 */
    display: block;
    position: absolute;
    background-color: #0f0f0f;
    min-width: 220px;
    top: calc(100% + 4px); /* 缩小间隙 */
    left: 50%;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 6px 0;
    opacity: 0;
    transform: translateX(-50%) translateY(-8px);
    pointer-events: auto; /* 改为 auto，始终可交互 */
    transition: opacity 0.15s ease, transform 0.15s ease, visibility 0.15s ease;
    box-shadow: 0 6px 18px rgba(0,0,0,0.6);
    z-index: 200;
    visibility: hidden; /* 隐藏时用 visibility 而不是只用 opacity */
}

.dropdown-content a {
    display: block;
    padding: 10px 14px;
    margin: 0;
    font-size: 0.95rem;
    color: var(--text-color);
    transition: background-color 0.12s ease, color 0.12s ease;
}

.dropdown-content a:hover {
    background-color: rgba(136,136,136,0.06);
    color: var(--accent-color);
}

/* 在 hover 或 .open 时显示下拉（支持点击切换 .open） */
.dropdown:hover .dropdown-content,
.dropdown.open .dropdown-content {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
    visibility: visible; /* 显示时恢复 visibility */
}

/* 更好的位置与尺寸在小屏上 */
@media (max-width: 768px) {
    .dropdown-content {
        position: fixed;
        left: 12px;
        right: 12px;
        top: 72px; /* 显示在 header 下方的固定位置 */
        transform: translateY(0);
        min-width: auto;
        width: auto;
        border-radius: 8px;
    }
    .dropdown:hover .dropdown-content,
    .dropdown.open .dropdown-content {
        opacity: 1;
        pointer-events: auto;
    }
}

/* 响应式 - 大屏幕 */
@media (min-width: 1400px) {
    header {
        padding: 30px 80px;
    }
}

@media (min-width: 1800px) {
    header {
        padding: 30px 100px;
    }
}

/* 中等屏幕 */
@media (max-width: 1024px) {
    header {
        padding: 25px 40px;
    }
    
    .logo {
        font-size: 2.2rem;
    }
    
    nav a {
        font-size: 1.2rem;
        margin-left: 25px;
    }
}

/* 平板 */
@media (max-width: 768px) {
    header {
        padding: 20px 30px;
    }
    
    .logo {
        font-size: 1.6rem;
    }
    
    nav a {
        margin-left: 18px;
        font-size: 0.9rem;
    }
    
    .dropdown-content {
        font-size: 0.85rem;
    }
}

/* 手机 */
@media (max-width: 480px) {
    header {
        padding: 15px 20px;
    }
    
    .logo {
        font-size: 1.2rem;
        letter-spacing: -0.5px;
    }
    
    nav {
        width: 100%;
        justify-content: space-between;
        gap: 8px;
    }
    
    nav a {
        margin-left: 0;
        font-size: 0.65rem;
        padding: 4px 6px;
    }
    
    .dropdown-content {
        font-size: 0.75rem;
        padding: 4px 0;
    }
    
    .dropdown-content a {
        padding: 8px 12px;
    }
}