/* ============================================================
   MASTHEAD — wordmark, section nav, theme toggle
   ============================================================ */

.masthead {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1.1rem var(--gutter);
  backdrop-filter: blur(14px) saturate(1.1);
  -webkit-backdrop-filter: blur(14px) saturate(1.1);
  border-bottom: 1px solid transparent;
  transition: border-color 300ms ease, background-color 300ms ease;
}
.masthead.is-stuck {
  border-bottom-color: var(--line-2);
  background: color-mix(in srgb, var(--bg-1) 72%, transparent);
}
@media (min-width: 960px) {
  .masthead { padding-left: calc(var(--rail) + 1.5rem); }
}

.wordmark {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  text-decoration: none;
  color: var(--ink);
}
.wordmark svg { width: 26px; height: 26px; overflow: visible; }
.wordmark svg [stroke] { stroke: var(--accent); }
.wordmark-text {
  font-family: var(--f-display);
  font-weight: 600;
  font-size: 1.02rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  line-height: 1;
}
.wordmark-text i {
  font-style: normal;
  color: var(--ink-3);
  font-weight: 400;
}

.nav { display: none; gap: 1.9rem; align-items: center; }
@media (min-width: 760px) { .nav { display: flex; } }
.nav a {
  font-family: var(--f-mono);
  font-size: 0.68rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-2);
  text-decoration: none;
  padding: 0.35rem 0;
  border-bottom: 1px solid transparent;
  transition: color 180ms ease, border-color 180ms ease;
}
.nav a:hover { color: var(--ink); border-bottom-color: var(--accent); }

.theme-toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  background: none;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.34rem 0.8rem;
  cursor: pointer;
  font-family: var(--f-mono);
  font-size: 0.62rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-2);
  transition: border-color 180ms ease, color 180ms ease;
}
.theme-toggle:hover { border-color: var(--accent); color: var(--ink); }