/* Shared ZB.DEV header — one set of dimensions for both Home and Labs.
   Both EJS layouts load this last. Only the theme tokens change between pages. */
body.site-body {
  --nav-ink: var(--ink);
  --nav-accent: var(--accent-dark);
  --nav-rule: var(--rule);
  --nav-fine-rule: var(--fine-rule);
  --nav-bg: var(--bg);
}
body.labs {
  --nav-ink: var(--lab-ink);
  --nav-accent: var(--lab-accent);
  --nav-rule: var(--lab-rule);
  --nav-fine-rule: var(--lab-faint);
  --nav-bg: var(--lab-bg);
}

/* Keep the centered navigation in the same position on pages with and
   without a vertical scrollbar (where the browser supports it). */
html { scrollbar-gutter: stable; }

.frame-corner {
  position: fixed;
  z-index: 50;
  width: 26px;
  height: 26px;
  pointer-events: none;
}
.frame-corner::before, .frame-corner::after {
  content: '';
  position: absolute;
  background: var(--nav-ink);
}
.frame-corner::before { width: 26px; height: 1.5px; }
.frame-corner::after { width: 1.5px; height: 26px; }
.frame-corner.tl { top: 19px; left: 24px; }
.frame-corner.tr { top: 19px; right: 24px; transform: scaleX(-1); }
.frame-corner.bl { bottom: 19px; left: 24px; transform: scaleY(-1); }
.frame-corner.br { bottom: 19px; right: 24px; transform: scale(-1,-1); }

.site-header { position: relative; z-index: 60; }
.header-inner {
  max-width: 1220px;
  min-height: 77px;
  padding: 0 24px;
  margin: auto;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
}
.site-brand {
  justify-self: start;
  font: 600 12px 'IBM Plex Mono', ui-monospace, SFMono-Regular, Consolas, monospace;
  letter-spacing: .02em;
  color: var(--nav-ink);
  white-space: nowrap;
  text-decoration: none;
}
.site-brand:hover { color: var(--nav-accent); }
.top-nav {
  grid-column: 2;
  display: flex;
  align-items: center;
  gap: clamp(17px, 3vw, 45px);
  font: 500 12px 'IBM Plex Mono', ui-monospace, SFMono-Regular, Consolas, monospace;
  letter-spacing: .005em;
  text-transform: uppercase;
}
.top-nav a {
  display: flex;
  align-items: center;
  gap: 9px;
  position: relative;
  padding: 24px 0 20px;
  color: var(--nav-ink);
  white-space: nowrap;
  text-decoration: none;
  border-bottom: 2px solid transparent;
  transition: color .18s, border-color .18s;
}
.top-nav a.active { color: var(--nav-accent); border-color: var(--nav-ink); }
.top-nav a:hover { color: var(--nav-accent); }
.nav-num { color: inherit; }
.nav-divider { width: 1px; height: 29px; background: var(--nav-ink); margin: 0 0 0 7px; }
.nav-lab { margin-left: 2px; }
.nav-toggle { display: none; }

@media (max-width: 1100px) {
  .header-inner { max-width: 1020px; }
}
@media (max-width: 820px) {
  .frame-corner { display: none; }
  .header-inner { grid-template-columns: 1fr auto; min-height: 69px; }
  .nav-toggle {
    display: flex;
    z-index: 3;
    grid-column: 2;
    width: 42px;
    height: 42px;
    border: 1px solid var(--nav-rule);
    background: transparent;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    align-items: center;
    cursor: pointer;
    color: var(--nav-ink);
  }
  .nav-toggle span { display: block; width: 20px; height: 1.5px; background: var(--nav-ink); }
  .top-nav {
    display: none;
    position: absolute;
    top: 68px;
    left: 24px;
    right: 24px;
    grid-column: auto;
    background: var(--nav-bg);
    border: 1px solid var(--nav-rule);
    padding: 14px 25px;
    box-shadow: 0 17px 35px #0002;
    z-index: 2;
  }
  .top-nav.is-open { display: flex; flex-direction: column; align-items: stretch; gap: 0; }
  .top-nav a { padding: 14px 0; border-bottom: 1px solid var(--nav-fine-rule); }
  .top-nav a.active { border-bottom-color: var(--nav-accent); }
  .nav-divider { display: none; }
}
@media (max-width: 560px) {
  .header-inner { padding-left: 18px; padding-right: 18px; }
  .top-nav { left: 18px; right: 18px; }
}
@media (prefers-reduced-motion: reduce) {
  .top-nav a { transition: none; }
}