header{
  position:sticky;
  top:0;
  z-index:50;
  backdrop-filter: blur(14px);
  background:rgba(255,255,255,.92);
  border-bottom:1px solid rgba(16,35,63,.06);
  box-shadow:0 4px 20px rgba(24,55,110,.08);
}

.nav{
  height:78px;
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:20px;
}

.brand{
  font-size:30px;
  font-weight:800;
  color:#153666;
  letter-spacing:-.04em;
}

.nav-links{
  display:flex;
  align-items:center;
  gap:28px;
  color:#244064;
  font-weight:500;
}

.nav-links a{
  position:relative;
  padding:6px 0;
}

.nav-links a::after{
  content:"";
  position:absolute;
  left:0;
  bottom:-2px;
  width:0;
  height:2px;
  border-radius:4px;
  background:var(--blue);
  transition:.25s ease;
}

.nav-links a:hover::after{width:100%}

.nav-item{position:relative}
.nav-parent{position:relative}

.nav-dropdown{
  position:fixed;
  left:0;
  right:0;
  top:78px;
  background:#fff;
  box-shadow:0 8px 32px rgba(24,55,110,.12);
  padding:32px 0;
  opacity:0;
  visibility:hidden;
  transform:translateY(-10px);
  transition:.3s ease;
  z-index:100;
}

.nav-item:hover .nav-dropdown,
.nav-dropdown:hover{
  opacity:1;
  visibility:visible;
  transform:translateY(0);
}

.dropdown-grid{
  display:grid;
  grid-template-columns:repeat(4, 1fr);
  gap:20px;
  max-width:1200px;
  margin:0 auto;
  padding:0 24px;
}

.dropdown-item{
  display:flex;
  flex-direction:column;
  padding:16px 20px 16px 32px;
  border-radius:12px;
  transition:.2s ease;
}

.dropdown-item:hover{
  background:var(--blue-soft);
}

.dropdown-title{
  font-size:16px;
  font-weight:600;
  color:var(--text);
  padding-left:10px;
}

.dropdown-desc{
  font-size:13px;
  color:var(--muted);
  margin-top:4px;
  padding-left:10px;
}

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

.search-toggle{
  background:none;
  border:none;
  cursor:pointer;
  padding:8px;
  color:var(--text);
  display:flex;
  align-items:center;
  justify-content:center;
  transition:.2s ease;
}

.search-toggle:hover{
  color:var(--blue);
}

.search-box{
  position:absolute;
  right:100%;
  top:50%;
  transform:translateY(-50%);
  display:flex;
  align-items:center;
  background:#fff;
  border-radius:8px;
  box-shadow:0 4px 20px rgba(24,55,110,.15);
  padding:8px 12px;
  opacity:0;
  visibility:hidden;
  margin-right:10px;
  transition:.3s ease;
}

.nav-search.active .search-box{
  opacity:1;
  visibility:visible;
}

.search-box input{
  border:none;
  outline:none;
  font-size:14px;
  width:200px;
  padding:8px;
}

.search-close{
  background:none;
  border:none;
  cursor:pointer;
  padding:4px;
  color:var(--muted);
  display:flex;
}

.search-close:hover{
  color:var(--text);
}

header .container{
  width:min(calc(100% - 40px), 1240px);
  margin:auto;
}

@media (max-width: 768px) {
  .nav { height: 70px; }
  .nav-links { display: none; }
  header .container {
    width: min(calc(100% - 28px), 1240px);
  }
}

/* 移动端汉堡菜单按钮 */
.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 16px;
  z-index: 101;
  position: relative;
  margin-left: auto;
  margin-right: 0;
  width: 48px;
  height: 48px;
  box-sizing: border-box;
}

.mobile-menu-toggle span {
  width: 24px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: all 0.3s ease;
  position: relative;
}

.mobile-menu-toggle.active span:nth-child(1) {
  transform: rotate(45deg) translateY(6px) translateX(6px);
}

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

.mobile-menu-toggle.active span:nth-child(3) {
  transform: rotate(-45deg) translateY(-6px) translateX(6px);
}

/* 移动端导航菜单 */
.mobile-nav {
  display: none;
  position: absolute;
  top: calc(100% + 0px);
  left: 0;
  right: 0;
  background: #fff;
  box-shadow: 0 8px 32px rgba(24, 55, 110, 0.12);
  flex-direction: column;
  padding: 16px 0;
  z-index: 100;
}

.mobile-nav a {
  padding: 14px 24px;
  color: var(--text);
  font-weight: 500;
  border-bottom: 1px solid rgba(23, 64, 124, 0.06);
  text-decoration: none;
}

.mobile-nav a:last-child {
  border-bottom: none;
}

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

@media (max-width: 768px) {
  .mobile-menu-toggle {
    display: flex;
  }
  .mobile-nav {
    display: none;
  }
  .mobile-nav.active {
    display: flex;
  }
}