/* Sticky, translucent site header with section nav and theme toggle. */

.skip-link {
  position: absolute;
  top: var(--space-2);
  left: var(--space-2);
  z-index: 100;
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius);
  background-color: var(--primary);
  color: var(--primary-foreground);
  transform: translateY(-200%);
}

.skip-link:focus-visible {
  transform: none;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  border-bottom: var(--hairline) solid var(--border);
  background-color: var(--header-bg);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
}

.site-header__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  column-gap: var(--space-5);
  min-height: 3.5rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--foreground);
  text-decoration: none;
}

.brand:hover {
  color: var(--foreground);
}

.brand__mark {
  width: 1.75rem;
  height: 1.75rem;
  color: var(--primary);
}

.brand__name {
  font-weight: 650;
  letter-spacing: -0.01em;
}

.site-nav {
  margin-left: auto;
}

.site-nav__list {
  display: flex;
  gap: var(--space-5);
  padding: 0;
  list-style: none;
}

.site-nav a {
  display: block;
  padding-block: var(--space-1);
  /* A transparent border reserves the underline's space so hover doesn't shift text. */
  border-bottom: 2px solid transparent;
  color: var(--muted-foreground);
  font-size: var(--text-sm);
  text-decoration: none;
  white-space: nowrap;
  transition: color 150ms ease, border-color 150ms ease;
}

.site-nav a:hover {
  border-bottom-color: var(--primary);
  color: var(--foreground);
}

.theme-toggle {
  display: inline-grid;
  place-items: center;
  width: 2.25rem;
  height: 2.25rem;
  padding: 0;
  border: var(--hairline) solid var(--border);
  border-radius: var(--radius-pill);
  background-color: var(--card);
  color: var(--muted-foreground);
  cursor: pointer;
  transition: color 150ms ease, border-color 150ms ease;
}

.theme-toggle:hover {
  border-color: var(--primary);
  color: var(--foreground);
}

.theme-toggle__icon {
  width: 1.125rem;
  height: 1.125rem;
}

.theme-toggle__icon--sun,
[data-theme="dark"] .theme-toggle__icon--moon {
  display: none;
}

[data-theme="dark"] .theme-toggle__icon--sun {
  display: block;
}

/* Small screens: nav drops to its own row and scrolls sideways. */
@media (max-width: 40rem) {
  .site-header__inner {
    justify-content: space-between;
    padding-top: var(--space-2);
  }

  .site-nav {
    order: 3;
    flex-basis: 100%;
    margin-left: 0;
    overflow-x: auto;
    border-top: var(--hairline) solid var(--border);
  }

  .site-nav__list {
    gap: var(--space-4);
    padding-block: var(--space-2);
  }
}