/* ==========================================================================
   nav.css — top nav + full-width mega menu dropdown
   Visual style matches v1.0 2d archive (full-width panel, gold left border
   on item hover, dim uppercase category header, no caret arrows).
   ========================================================================== */

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  z-index: var(--z-nav);
  opacity: 0;
  transform: translateY(-12px);
  pointer-events: none;
  transition: opacity var(--dur-slow) var(--ease-out),
              transform var(--dur-slow) var(--ease-out);
  background: rgba(7, 12, 20, 0.7);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

body.page--revealed .site-header {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  padding-inline: clamp(var(--space-5), 4vw, var(--space-7));
}

/* ----- Brand ----- */
.nav__brand {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 1rem;
  letter-spacing: 0.5px;
  color: rgba(255, 255, 255, 0.9);
  white-space: nowrap;
  text-decoration: none;
  opacity: 0.9;
  transition: opacity 0.2s;
}

.nav__brand:hover {
  opacity: 1;
}

/* ----- Nav list (no gap — items are full-height siblings) ----- */
.nav__list {
  display: flex;
  align-items: center;
  gap: 0;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav__item {
  position: relative;
}

/* IMPORTANT: a dropdown parent is `position: static` so the mega-menu panel
   can anchor to .site-header (its nearest positioned ancestor) and span the
   full viewport width. */
.nav__item.has-dropdown {
  position: static;
}

/* ----- Trigger link (plain text, no caret, no pill border — font style only) ----- */
.nav__link {
  display: inline-flex;
  align-items: center;
  height: var(--nav-height);
  padding: 0 1rem;
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 400;
  letter-spacing: 0.3px;
  color: rgba(255, 255, 255, 0.55);
  background: transparent;
  border: none;
  border-radius: 0;
  cursor: pointer;
  white-space: nowrap;
  user-select: none;
  text-decoration: none;
  transition: color 0.25s;
}

.nav__link:hover,
.nav__link.is-open {
  color: rgba(255, 255, 255, 0.85);
  background: transparent;
  border-color: transparent;
}

/* Caret hidden — clean text-only triggers. */
.nav__caret {
  display: none;
}

/* ----- Icon-only link (e.g. GitHub) — square button, icon centered ----- */
.nav__link--icon {
  width: var(--nav-height);
  padding: 0;
  justify-content: center;
  color: rgba(255, 255, 255, 0.55);
}

.nav__link--icon svg {
  display: block;
  opacity: 0.75;
  transition: opacity 0.2s, transform 0.2s;
}

.nav__link--icon:hover,
.nav__link--icon:focus-visible {
  color: rgba(255, 255, 255, 0.95);
  background: transparent;
  border-color: transparent;
}

.nav__link--icon:hover svg,
.nav__link--icon:focus-visible svg {
  opacity: 1;
  transform: scale(1.08);
}

/* ----- Mega menu panel (full viewport width) ----- */
.nav-dropdown {
  position: absolute;
  top: 100%;
  left: 0;
  width: 100vw;
  padding: 2rem 0;
  background: rgba(12, 12, 13, 0.75);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-top: 1px solid rgba(255, 255, 255, 0.06);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transition: opacity 0.25s ease,
              visibility 0s linear 0.25s;
  z-index: var(--z-dropdown);
}

.nav__item.is-open .nav-dropdown {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transition: opacity 0.25s ease,
              visibility 0s linear 0s;
}

.nav-dropdown__inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 clamp(var(--space-5), 4vw, var(--space-7));
  display: flex;
  gap: clamp(var(--space-6), 6vw, var(--space-8));
}

.nav-dropdown__column {
  flex: 0 0 auto;
  min-width: 180px;
}

/* Small uppercase category header — matches archive's h4.dropdown-category */
.nav-dropdown__category {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: rgba(255, 255, 255, 0.3);
  margin: 0 0 0.8rem 0;
  padding: 0;
  border: none;
  background: transparent;
}

/* List inside the panel — flat, no card look */
.nav-dropdown__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: block;
}

.nav-dropdown__item {
  display: block;
  margin: 0;
}

/* Each link: hover shifts right + gold left border — archive signature */
.nav-dropdown__link {
  display: block;
  padding: 0.5rem 0;
  color: rgba(255, 255, 255, 0.6);
  font-size: 0.85rem;
  text-decoration: none;
  border-left: 2px solid transparent;
  padding-left: 0;
  background: transparent;
  transition: color 0.2s,
              padding-left 0.2s,
              border-left-color 0.2s;
  border-radius: 0;
}

.nav-dropdown__link::after {
  display: none;
}

.nav-dropdown__link:hover,
.nav-dropdown__link:focus-visible {
  color: rgba(255, 255, 255, 0.95);
  background: transparent;
  padding-left: 0.5rem;
  border-left-color: var(--color-accent-1); /* warm gold */
}

/* Empty / placeholder state — used while a dropdown is intentionally bare
   (e.g. waiting for sub-sites to launch). Not a link, no hover affordance. */
.nav-dropdown__item--empty {
  pointer-events: none;
}

.nav-dropdown__empty {
  display: block;
  padding: 0.5rem 0;
  color: rgba(255, 255, 255, 0.32);
  font-size: 0.85rem;
  font-style: italic;
  letter-spacing: 0.04em;
  cursor: default;
  user-select: none;
}

/* ----- Language switch (中文 | EN — split switcher, archive v1.0 2d style) ----- */
.nav__lang {
  display: inline-flex;
  align-items: center;
  height: var(--nav-height);
  padding: 0 1rem;
  gap: 0.4rem;
  font-family: var(--font-body);
  font-size: 0.78rem;
  color: rgba(255, 255, 255, 0.4);
  letter-spacing: 0.5px;
  white-space: nowrap;
  user-select: none;
}

.nav__lang-option {
  display: inline-block;
  padding: 0;
  color: rgba(255, 255, 255, 0.4);
  font: inherit;
  letter-spacing: inherit;
  text-decoration: none;
  background: transparent;
  border: none;
  cursor: pointer;
  transition: color 0.2s;
}

.nav__lang-option:hover,
.nav__lang-option:focus-visible {
  color: rgba(255, 255, 255, 0.7);
}

.nav__lang-option.is-active {
  color: rgba(255, 255, 255, 0.85);
  cursor: default;
  pointer-events: none;
}

.nav__lang-divider {
  color: rgba(255, 255, 255, 0.2);
  font-weight: 300;
  user-select: none;
}

/* ----- Mobile menu toggle ----- */
.nav__menu-toggle {
  display: none;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-line);
  border-radius: var(--r-pill);
  color: var(--color-text);
}

@media (max-width: 767px) {
  .nav__list { display: none; }
  .nav__menu-toggle { display: inline-flex; }
}