/* 头部整体样式 */
.site-header {
    width: 100%;
    background-color: #1a1a1a;
    color: #fff;
    padding: 12px 0;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    position: relative;
    top: 0;
    left: 0;
    z-index: 9999;
    /* 优化1：延长过渡时间，增加贝塞尔曲线让动画更自然 */
    transition: all 0.4s cubic-bezier(0.25, 0.1, 0.25, 1);
    will-change: padding, background-color, box-shadow; /* 告诉浏览器提前准备动画 */
}

/* 滚动固定样式 */
.site-header.sticky {
    position: fixed;
    padding: 8px 0; /* 减少的padding值更小，变化更柔和 */
    background-color: rgba(26, 26, 26, 0.98); /* 更高透明度，变化更细微 */
    box-shadow: 0 3px 12px rgba(0, 0, 0, 0.4);
    /* 优化2：添加微小的缩放效果，视觉上更连贯 */
    transform: translateY(0);
}

/* 未滚动时的初始状态（用于对比过渡） */
.site-header:not(.sticky) {
    transform: translateY(0);
}

/* 内容区补偿（关键：避免布局跳动） */
.site-main {
    /* 优化3：使用精确的初始高度计算，避免跳动 */
    padding-top: calc(12px*2 + 56px); /* 原header总高度（上下padding+内容高度） */
    transition: padding-top 0.4s cubic-bezier(0.25, 0.1, 0.25, 1);
}

/* 当导航固定时，同步调整内容区间距 */
.site-header.sticky ~ .site-main {
    padding-top: calc(8px*2 + 56px); /* 固定后的header总高度 */
}

/* 其他原有样式保持不变 */
.header-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.desktop-nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.site-logo {
    color: #fff;
    text-decoration: none;
    font-size: 24px;
    font-weight: bold;
    display: flex;
    align-items: center;
    gap: 8px;
}

.site-logo i {
    color: #ff4d4d;
    font-size: 28px;
}

.main-nav {
    display: flex;
    list-style: none;
    gap: 25px;
    margin: 0;
    padding: 0;
}

.main-nav li a {
    color: #e0e0e0;
    text-decoration: none;
    font-size: 16px;
    padding: 8px 0;
    position: relative;
}

.main-nav li a:hover {
    color: #fff;
}

.main-nav li a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background-color: #ff4d4d;
    transition: width 0.3s;
}

.main-nav li a:hover::after {
    width: 100%;
}

.search-form {
    display: flex;
    align-items: center;
    position: relative;
}

.search-input {
    padding: 8px 15px;
    border: none;
    border-radius: 4px 0 0 4px;
    font-size: 14px;
    outline: none;
    width: 180px;
    box-sizing: border-box;
    background-color: #333;
    color: #fff;
}

.search-input::placeholder {
    color: #aaa;
}

.search-btn {
    padding: 8px 15px;
    background-color: #ff4d4d;
    color: white;
    border: none;
    border-radius: 0 4px 4px 0;
    cursor: pointer;
    font-size: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.search-btn i {
    margin: 0;
}

.desktop-search {
    width: 220px;
}

.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    color: #fff;
    font-size: 24px;
    cursor: pointer;
}

.mobile-nav {
    display: none;
    padding: 15px 20px;
    background-color: #1a1a1a;
    border-top: 1px solid #333;
}

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

.mobile-nav-list {
    list-style: none;
    margin: 0;
    padding: 0;
}

.mobile-nav-list li {
    margin-bottom: 12px;
}

.mobile-nav-list li a {
    color: #e0e0e0;
    text-decoration: none;
    font-size: 16px;
    display: block;
    padding: 8px 0;
}

.mobile-nav-list li a:hover {
    color: #fff;
}

.mobile-search {
    margin-top: 10px;
    padding-top: 10px;
    border-top: 1px solid #333;
}

.mobile-search .search-input {
    width: calc(100% - 60px);
}

@media (max-width: 768px) {
    .main-nav, .desktop-search {
        display: none;
    }
    
    .mobile-menu-toggle {
        display: block;
    }
    
    /* 移动端滚动样式优化 */
    .site-header.sticky {
        padding: 6px 0;
    }
    
    .site-main {
        padding-top: calc(12px*2 + 50px);
    }
    
    .site-header.sticky ~ .site-main {
        padding-top: calc(6px*2 + 50px);
    }
}