/* Header on scroll (10/23): see-through only at the very top of a page.
   Scrolling down slides the whole header away, Book button included;
   scrolling up brings it back on a solid dark bar so it never sits on text. */
header {
  border-bottom: 1px solid transparent;
  transition: transform 0.35s ease, background-color 0.35s ease, border-color 0.35s ease;
}
body.header-scrolled header {
  background: rgba(10,15,26,0.96);
  -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px);
  border-bottom-color: rgba(184,196,212,0.12);
}
body.header-hidden header { transform: translateY(-100%); }
body.menu-open header { transform: none; }