/* ==========================================================================
   Aged Science LLC — Navigation
   Fixed hairline bar on desktop; full-screen overlay on mobile.
   ========================================================================== */

.nav {
  position: fixed;
  top: 0;
  right: 0;
  left: 0;
  z-index: 100;
  border-bottom: 1px solid var(--color-line);
  background-color: rgba(10, 10, 10, 0.86);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  padding-top: env(safe-area-inset-top);
}

.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  height: 4.25rem;
}

/* Wordmark ------------------------------------------------------------- */

.nav__brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  font-size: 0.8125rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  white-space: nowrap;
  transition: color var(--duration-fast) var(--ease-out);
}

.nav__brand:hover {
  color: var(--color-accent-bright);
}

.nav__brand-mark {
  width: 0.5rem;
  height: 0.5rem;
  background-color: var(--color-accent);
  transition: background-color var(--duration-fast) var(--ease-out);
}

.nav__brand:hover .nav__brand-mark {
  background-color: var(--color-accent-bright);
}

/* Desktop links -------------------------------------------------------- */

.nav__list {
  display: none;
  align-items: center;
  gap: 2rem;
}

.nav__link {
  position: relative;
  display: block;
  padding-block: 0.35rem;
  font-size: var(--text-small);
  font-weight: 500;
  color: var(--color-text-muted);
  transition: color var(--duration-fast) var(--ease-out);
}

.nav__link:hover {
  color: var(--color-text);
}

.nav__link.is-active {
  color: var(--color-accent-bright);
}

.nav__link.is-active::after {
  content: "";
  position: absolute;
  right: 0;
  bottom: -0.35rem;
  left: 0;
  height: 2px;
  background-color: var(--color-accent);
}

/* Menu toggle ---------------------------------------------------------- */

.nav__toggle {
  display: inline-flex;
  flex: none;
  flex-direction: column;
  justify-content: center;
  gap: 0.3rem;
  width: 2.75rem;
  height: 2.75rem;
  padding: 0 0.55rem;
  border: 1px solid var(--color-line);
  background-color: transparent;
  cursor: pointer;
  transition: border-color var(--duration-fast) var(--ease-out);
}

.nav__toggle:hover {
  border-color: var(--color-accent);
}

.nav__toggle-bar {
  display: block;
  width: 100%;
  height: 1px;
  background-color: var(--color-text);
  transition: transform var(--duration-normal) var(--ease-out),
    opacity var(--duration-fast) var(--ease-out);
}

.nav__toggle[aria-expanded="true"] .nav__toggle-bar:nth-child(1) {
  transform: translateY(0.4rem) rotate(45deg);
}

.nav__toggle[aria-expanded="true"] .nav__toggle-bar:nth-child(2) {
  opacity: 0;
}

.nav__toggle[aria-expanded="true"] .nav__toggle-bar:nth-child(3) {
  transform: translateY(-0.4rem) rotate(-45deg);
}

/* Mobile overlay ------------------------------------------------------- */

.nav__overlay {
  position: fixed;
  inset: 0;
  z-index: 99;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 5rem max(var(--space-gutter), env(safe-area-inset-left))
    calc(2rem + env(safe-area-inset-bottom));
  background-color: var(--color-bg);
  overscroll-behavior: contain;
  overflow-y: auto;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-0.75rem);
  transition: opacity var(--duration-normal) var(--ease-out),
    transform var(--duration-normal) var(--ease-out),
    visibility var(--duration-normal) var(--ease-out);
}

.nav__overlay.is-open {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.nav__overlay-list {
  border-top: 1px solid var(--color-line);
}

.nav__overlay-item {
  border-bottom: 1px solid var(--color-line);
}

.nav__overlay-link {
  display: flex;
  align-items: baseline;
  gap: 1rem;
  padding-block: 1.15rem;
  font-size: clamp(1.75rem, 8vw, 2.5rem);
  font-weight: 700;
  letter-spacing: -0.035em;
  text-transform: uppercase;
  transition: color var(--duration-fast) var(--ease-out);
}

.nav__overlay-link:hover {
  color: var(--color-accent-bright);
}

.nav__overlay-link.is-active {
  color: var(--color-accent-bright);
}

.nav__overlay-index {
  font-family: var(--font-mono);
  font-size: var(--text-label);
  font-variant-numeric: tabular-nums;
  font-weight: 500;
  letter-spacing: 0.16em;
  color: var(--color-text-dim);
}

.nav__overlay-meta {
  margin-top: 2.5rem;
  font-family: var(--font-mono);
  font-size: var(--text-label);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--color-text-dim);
}

/* Locks background scroll while the overlay is open. */
body.is-nav-open {
  overflow: hidden;
}

/* Desktop breakpoint --------------------------------------------------- */

@media (min-width: 52rem) {
  .nav__list {
    display: flex;
  }

  .nav__toggle {
    display: none;
  }

  .nav__overlay {
    display: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  .nav__overlay {
    transform: none;
  }
}