.site-header {
  position: sticky;
  top: 0;
  background: var(--color-background);
  border-bottom: 1px solid var(--color-border);
  z-index: 50;
  transition: background var(--transition-normal);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}
.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 1.2rem;
}
.logo svg {
  color: var(--color-primary);
}
.nav-menu {
  display: flex;
  gap: 1.2rem;
}
.nav-menu a {
  font-size: 0.9rem;
  color: var(--color-muted);
  padding: 0.3rem 0;
  border-bottom: 2px solid transparent;
  transition: color var(--transition-fast), border-color var(--transition-fast);
}
.nav-menu a:hover,
.nav-menu a[aria-current="page"] {
  color: var(--color-text);
  border-color: var(--color-primary);
}
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: space-around;
  width: 30px;
  height: 24px;
  padding: 0;
}
.nav-toggle .bar {
  width: 100%;
  height: 2px;
  background: var(--color-text);
  transition: transform var(--transition-fast), opacity var(--transition-fast);
}
.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}
.icon-sun, .icon-moon {
  display: none;
}
[data-theme="dark"] .icon-sun { display: block; }
[data-theme="dark"] .icon-moon { display: none; }
[data-theme="light"] .icon-sun { display: none; }
[data-theme="light"] .icon-moon { display: block; }