/* Let the island's white border fade to transparent while the navigation
 * expands into its flat top-of-page state. The scrolled border utility keeps
 * higher specificity and therefore remains unchanged at rest. */
header > nav {
  border-color: transparent;
}

@media (prefers-reduced-motion: reduce) {
  header > nav {
    transition-duration: 0.01ms !important;
  }
}