/* 顶栏与二级下拉菜单 */
#site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: transparent;
  backdrop-filter: none;
  border-bottom: none;
  box-shadow: none;
}

.nav-inner {
  width: min(1120px, 100% - 32px);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: var(--header-h);
  gap: 16px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--color-text);
  text-decoration: none;
  flex-shrink: 0;
}

.nav-brand:hover {
  text-decoration: none;
}

.nav-logo {
  width: auto;
  height: 44px;
  object-fit: contain;
}

.nav-brand-text {
  font-weight: 700;
  font-size: 1.125rem;
  color: var(--color-primary-dark);
}

.nav-main {
  display: flex;
  align-items: stretch;
  gap: 4px;
}

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

.nav-link {
  display: block;
  padding: 12px 14px;
  color: var(--color-text);
  font-weight: 500;
  font-size: 0.9375rem;
  border-radius: 6px;
  text-decoration: none;
  white-space: nowrap;
}

.nav-link:hover,
.nav-item.is-active > .nav-link {
  color: var(--color-primary);
  background: rgba(10, 79, 140, 0.06);
  text-decoration: none;
}

.nav-link--parent {
  position: relative;
  padding-right: 28px;
}

.nav-chevron {
  position: absolute;
  right: 10px;
  top: 50%;
  margin-top: -2px;
  width: 0;
  height: 0;
  border-left: 4px solid transparent;
  border-right: 4px solid transparent;
  border-top: 5px solid var(--color-muted);
}

.nav-item--has-sub:hover .nav-chevron,
.nav-item--has-sub:focus-within .nav-chevron {
  border-top-color: var(--color-primary);
}

/* 二级下拉 */
.nav-dropdown {
  position: absolute;
  left: 0;
  top: 100%;
  min-width: 200px;
  padding: 8px 0;
  background: #fff;
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
  border: 1px solid rgba(10, 79, 140, 0.1);
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: opacity 0.2s, transform 0.2s, visibility 0.2s;
  z-index: 1001;
}

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

.nav-sublink {
  display: block;
  padding: 10px 18px;
  color: var(--color-text);
  font-size: 0.9375rem;
  text-decoration: none;
}

.nav-sublink:hover {
  background: rgba(10, 79, 140, 0.08);
  color: var(--color-primary);
  text-decoration: none;
}

/* 移动端汉堡 */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 44px;
  height: 44px;
  padding: 0;
  border: none;
  background: transparent;
  cursor: pointer;
  border-radius: 8px;
}

.nav-toggle-bar {
  display: block;
  height: 3px;
  width: 24px;
  background: var(--color-primary-dark);
  border-radius: 2px;
  margin: 0 auto;
}

.nav-toggle:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

.nav-error {
  margin: 0;
  padding: 16px;
  color: #b00020;
}

@media (max-width: 959px) {
  .nav-toggle {
    display: flex;
  }

  .nav-main {
    position: fixed;
    top: var(--header-h);
    left: 0;
    right: 0;
    bottom: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 16px;
    background: rgba(255, 255, 255, 0.98);
    overflow-y: auto;
    transform: translateX(100%);
    transition: transform 0.25s ease;
    box-shadow: -4px 0 24px rgba(0, 0, 0, 0.08);
  }

  .nav-main.is-open {
    transform: translateX(0);
  }

  .nav-item {
    flex-direction: column;
    align-items: stretch;
    border-bottom: 1px solid rgba(0, 0, 0, 0.06);
  }

  .nav-link {
    white-space: normal;
    padding: 14px 12px;
  }

  .nav-link--parent {
    position: relative;
  }

  .nav-chevron {
    right: 12px;
    transform: rotate(0deg);
    transition: transform 0.2s;
  }

  .nav-link--parent[aria-expanded="true"] .nav-chevron {
    transform: rotate(180deg);
  }

  /* 移动端下拉为折叠 */
  .nav-dropdown {
    position: static;
    opacity: 1;
    visibility: visible;
    transform: none;
    box-shadow: none;
    border: none;
    padding: 0 0 8px 12px;
    display: none;
    min-width: auto;
  }

  .nav-dropdown.is-open {
    display: block;
  }

  .nav-item--has-sub:hover .nav-dropdown {
    display: none;
  }

  .nav-item--has-sub .nav-dropdown.is-open {
    display: block;
  }

  body.nav-mobile-open {
    overflow: hidden;
  }
}