.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: var(--z-sticky);
  height: var(--header-height);
  transition: var(--transition);
}

.header-inner {
  margin: 0 auto;
  padding: 0 clamp(1rem, 3vw, 3rem);
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

/* Glass effect lives on .header-inner (sibling of .mobile-nav), never on .site-header:
   backdrop-filter on the header would turn it into the containing block for the
   fixed-position mobile menu and collapse the menu to the header's height. */
.header-inner.header-glass {
  background: rgba(255, 255, 255, 0.72);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  transition: background 0.3s ease, box-shadow 0.3s ease;
}
.site-header.scrolled .header-inner,
.site-header.menu-open .header-inner {
  background: rgba(255, 255, 255, 0.96);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}

.header-logo {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  font-size: 1.125rem;
  font-weight: var(--fw-bold);
  color: var(--primary-dark);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.header-logo img {
  height: 28px;
  width: auto;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: 0;
}

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

.nav-item {
  /*position: relative;*/
  padding: 0 1.125rem;
  height: var(--header-height);
  display: flex;
  align-items: center;
}

.nav-link {
  font-size: var(--fs-small);
  font-weight: var(--fw-medium);
  color: var(--text-primary);
  transition: var(--transition-fast);
  white-space: nowrap;
}

.nav-link:hover {
  color: var(--accent);
}

.nav-item.active .nav-link {
  color: #1138D4;
}

.nav-link .arrow {
  display: inline-block;
  margin-left: 4px;
  font-size: 0.625rem;
  transition: var(--transition-fast);
}

.nav-item:hover .arrow {
  transform: rotate(180deg);
}

.mega-menu {
  position: fixed;      /* 修改点1：改为 fixed 定位，彻底脱离父级排版限制 */
  top: var(--header-height);
  left: 50%;
  transform: translateX(-50%);
  width: 1000px;
  max-width: 95vw;
  background: var(--bg-white);
  border-radius: 0 0 var(--radius-lg) var(--radius-lg);
  box-shadow: var(--shadow-xl);
  padding: 2rem;
  opacity: 0;
  visibility: hidden;
  transform: translateX(-50%) translateY(-8px);
  transition:
    opacity 0.25s ease,
    transform 0.25s ease,
    visibility 0.25s;
  border-top: 2px solid var(--accent);
}

.nav-item:hover .mega-menu {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) translateY(0);
}

.mega-menu-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
}

.mega-menu-group h4 {
  font-size: var(--fs-xs);
  font-weight: var(--fw-bold);
  color: rgba(17, 56, 212, 1);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 0.75rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border-light);
}

.mega-menu-group a {
  display: block;
  padding: 0.375rem 0;
  font-size: var(--fs-small);
  color: var(--text-secondary);
  transition: var(--transition-fast);
}

.mega-menu-group a:hover {
  color: var(--accent);
  padding-left: 4px;
}

.header-cta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.header-contact-btn {
  padding: 0.5rem 1.25rem;
  font-size: var(--fs-xs);
  font-weight: var(--fw-semibold);
  background: #1138D4;
  color: white;
  border-radius: var(--radius-full);
  transition: var(--transition);
}

.header-contact-btn:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
}

/* 默认状态：三条横杠 */
.mobile-toggle {
  display: none; /* 默认桌面端隐藏 */
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  z-index: 1001; /* 确保在最上层 */
  padding: 10px;
}

.mobile-toggle span {
  width: 25px;
  height: 2px;
  background-color: var(--primary-dark);
  transition: all 0.3s ease-in-out;
  display: block;
}

/* 激活状态：变成 X */
.mobile-toggle.open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.mobile-toggle.open span:nth-child(2) {
  opacity: 0;
}

.mobile-toggle.open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.mobile-nav {
  position: fixed;
  top: var(--header-height);
  left: 0;
  right: 0;
  bottom: 0;
  background: white;
  padding: 2rem;
  z-index: 1000;
  
  /* 初始隐藏状态：位移到右侧或渐隐 */
  opacity: 0;
  visibility: hidden;
  transform: translateX(100%); 
  transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.mobile-nav.open {
  opacity: 1;
  visibility: visible;
  transform: translateX(0); /* 点击后滑入 */
  overflow-y: auto;          /* 菜单项过多时在面板内滚动 */
}

/* 菜单打开时锁定页面滚动，避免背景页面跟着滚 */
body.menu-open {
  overflow: hidden;
}

/* 移动端菜单内的链接样式 */
.mobile-nav a {
  display: block;
  padding: 1.25rem 0;
  font-size: 1.25rem;
  font-weight: 500;
  color: var(--text-primary);
  border-bottom: 1px solid #eee;
  text-decoration: none;
}

@media (max-width: 960px) {
  /* 1. 隐藏桌面导航栏 */
  .header-nav {
    display: none !important;
  }

  /* 2. 彻底禁用 Mega Menu，防止代码冲突 */
  .mega-menu {
    display: none !important;
  }

  /* 3. 显示汉堡按钮 */
  .mobile-toggle {
    display: flex;
  }

  /* 4. 调整 Logo 尺寸（可选） */
  .header-logo img {
    height: 28px;
  }

  /* 5. 隐藏桌面端的 Contact Us 按钮（如果空间不够的话） */
  /* .header-cta { display: none; } */
}