/* ── Header ─────────────────────────────── */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  padding: 18px 0;
  border-bottom: 1px solid var(--border);
  background: rgba(247,250,251,0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: border-color 0.3s;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand-logo { height: 28px; width: auto; }

@media (min-width: 640px) {
  .brand-logo { height: 34px; }
}

nav ul {
  display: flex;
  gap: 32px;
  list-style: none;
  align-items: center;
}

nav a {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--ink-muted);
  transition: color 0.2s;
  letter-spacing: 0.02em;
}

nav a:hover, nav a.active { color: var(--coral); }