/* ===== 顶部导航 ===== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: rgba(255, 255, 255, 0.96);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid transparent;
  transition: all var(--transition-base);
}

.header.is-scrolled {
  border-bottom-color: var(--color-border);
  box-shadow: var(--shadow-sm);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--fs-2xl);
  font-weight: var(--fw-bold);
  color: var(--color-primary);
  letter-spacing: -0.02em;
}

.logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 2px 10px;
  background: linear-gradient(135deg, var(--color-primary) 0%, #4ba9f5 100%);
  color: #fff;
  border-radius: var(--radius-sm);
  font-style: italic;
}

.logo-text {
  color: var(--color-text);
}

.logo-tag {
  font-size: var(--fs-xs);
  color: var(--color-primary);
  font-weight: var(--fw-medium);
  vertical-align: super;
  margin-left: 2px;
}

/* Nav */
.nav {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

.nav-item {
  position: relative;
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: var(--fs-base);
  color: var(--color-text);
  padding: var(--space-2) 0;
  transition: color var(--transition-fast);
}

.nav-item:hover,
.nav-item.is-active {
  color: var(--color-primary);
}

.nav-item.is-active::after {
  content: "";
  position: absolute;
  left: 50%;
  bottom: -4px;
  transform: translateX(-50%);
  width: 24px;
  height: 2px;
  background-color: var(--color-primary);
  border-radius: 1px;
}

.nav-caret {
  font-size: 10px;
  transition: transform var(--transition-fast);
}

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

/* 下拉 */
.nav-dropdown {
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%) translateY(8px);
  min-width: 180px;
  background-color: #fff;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  padding: var(--space-2) 0;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-base);
}

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

.nav-dropdown a {
  display: block;
  padding: var(--space-3) var(--space-5);
  font-size: var(--fs-sm);
  color: var(--color-text-secondary);
  transition: all var(--transition-fast);
}

.nav-dropdown a:hover {
  background-color: var(--color-primary-light);
  color: var(--color-primary);
}

/* 右侧工具区 */
.header-tools {
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.lang-switch {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: var(--fs-sm);
  color: var(--color-text-secondary);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.lang-switch:hover {
  color: var(--color-primary);
  background-color: var(--color-bg-soft);
}

.lang-caret {
  font-size: 10px;
}

/* 移动端菜单按钮 */
.menu-toggle {
  display: none;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  font-size: var(--fs-xl);
  color: var(--color-text);
}

@media (max-width: 1024px) {
  .nav {
    display: none;
  }
  .menu-toggle {
    display: flex;
  }

  .header.is-mobile-open .nav {
    display: flex;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background-color: #fff;
    border-top: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
    padding: var(--space-2) 0;
  }

  .header.is-mobile-open .nav-item {
    padding: var(--space-4) var(--container-pad);
    border-bottom: 1px solid var(--color-border-light);
  }

  .header.is-mobile-open .nav-dropdown {
    position: static;
    transform: none;
    box-shadow: none;
    opacity: 1;
    visibility: visible;
    padding-left: var(--container-pad);
  }
}