/* ==========================================================================
   Header — sticky glass bar, primary nav, mega menu, theme toggle, mobile nav.
   ========================================================================== */

.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  background: var(--header-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
}

.site-header__inner {
  display: flex;
  align-items: center;
  gap: var(--space-5);
  height: 4.25rem;
}

/* ---- Brand --------------------------------------------------------------- */

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.7rem;
  flex: none;
}

.brand__mark { width: 2rem; height: 2rem; display: grid; }
.brand__mark svg { width: 100%; height: 100%; }
.brand__logo { width: 2.25rem; height: 2.25rem; border-radius: 0.5rem; object-fit: contain; }

.brand__text { display: grid; line-height: 1.15; }
.brand__name { font-weight: 700; font-size: var(--text-sm); color: var(--text-strong); letter-spacing: -0.01em; }
.brand__sub  { font-size: var(--text-xs); color: var(--text-faint); letter-spacing: 0.08em; text-transform: uppercase; }

/* ---- Primary nav ---------------------------------------------------------- */

.site-nav { margin-inline: auto; }

.site-nav__list {
  display: flex;
  align-items: center;
  gap: 0.15rem;
}

.site-nav__item { position: relative; }

.site-nav__link {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.55rem 0.85rem;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--text-muted);
  transition: color var(--duration-fast) var(--ease-out),
              background-color var(--duration-fast) var(--ease-out);
}

.site-nav__link:hover,
.site-nav__link.is-active {
  color: var(--text-strong);
  background: var(--surface);
}

.site-nav__link[aria-current="page"] { color: var(--text-strong); }

.site-nav__chevron {
  width: 0.8rem;
  height: 0.8rem;
  transition: transform var(--duration-base) var(--ease-out);
}

.site-nav__item--mega:hover .site-nav__chevron,
.site-nav__item--mega:focus-within .site-nav__chevron {
  transform: rotate(180deg);
}

/* ---- Mega menu ------------------------------------------------------------- */

.mega {
  position: absolute;
  top: calc(100% + 0.6rem);
  left: 50%;
  transform: translateX(-50%) translateY(-6px);
  width: min(56rem, 92vw);
  background: var(--glass);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-3);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--duration-base) var(--ease-out),
              transform var(--duration-base) var(--ease-out),
              visibility var(--duration-base);
  z-index: var(--z-mega);
}

.site-nav__item--mega:hover .mega,
.site-nav__item--mega:focus-within .mega,
.mega[data-open="true"] {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) translateY(0);
}

.mega__inner {
  display: grid;
  grid-template-columns: 15rem 1fr;
  gap: var(--space-6);
  padding: var(--space-6);
}

.mega__intro {
  display: grid;
  gap: var(--space-3);
  align-content: start;
  padding-right: var(--space-5);
  border-right: 1px solid var(--border);
}

.mega__intro-title { font-weight: 650; color: var(--text-strong); font-size: var(--text-sm); }
.mega__intro-text  { font-size: var(--text-sm); color: var(--text-muted); line-height: var(--leading-snug); }

.mega__columns {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-5);
}

.mega__column-title {
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  margin-bottom: var(--space-3);
}

.mega__items { display: grid; gap: 0.2rem; }

.mega__item {
  display: grid;
  gap: 0.15rem;
  padding: 0.55rem 0.7rem;
  border-radius: var(--radius-md);
  transition: background-color var(--duration-fast) var(--ease-out);
}

.mega__item:hover { background: var(--surface-2); }

.mega__item-label { font-size: var(--text-sm); font-weight: 600; color: var(--text-strong); }
.mega__item-desc  { font-size: var(--text-xs); color: var(--text-muted); line-height: var(--leading-snug); }

/* ---- Header actions ---------------------------------------------------------- */

.site-header__actions {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex: none;
}

.theme-toggle {
  display: inline-grid;
  place-items: center;
  width: 2.35rem;
  height: 2.35rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  color: var(--text-muted);
  transition: color var(--duration-fast) var(--ease-out),
              border-color var(--duration-fast) var(--ease-out),
              background-color var(--duration-fast) var(--ease-out);
}

.theme-toggle:hover {
  color: var(--text-strong);
  border-color: var(--border-strong);
  background: var(--surface);
}

.theme-toggle .icon { width: 1.05rem; height: 1.05rem; }

/* Show moon in dark (click -> light), sun in light */
.theme-toggle .icon--sun  { display: none; }
.theme-toggle .icon--moon { display: block; }
[data-theme="light"] .theme-toggle .icon--sun  { display: block; }
[data-theme="light"] .theme-toggle .icon--moon { display: none; }

/* ---- Burger -------------------------------------------------------------------- */

.nav-burger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 2.35rem;
  height: 2.35rem;
  padding: 0.55rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
}

.nav-burger__line {
  display: block;
  height: 1.5px;
  width: 100%;
  background: var(--text-strong);
  border-radius: var(--radius-full);
  transition: transform var(--duration-base) var(--ease-out),
              opacity var(--duration-base) var(--ease-out);
}

.nav-burger[aria-expanded="true"] .nav-burger__line:nth-child(1) { transform: translateY(6.5px) rotate(45deg); }
.nav-burger[aria-expanded="true"] .nav-burger__line:nth-child(2) { opacity: 0; }
.nav-burger[aria-expanded="true"] .nav-burger__line:nth-child(3) { transform: translateY(-6.5px) rotate(-45deg); }

/* ---- Mobile nav ------------------------------------------------------------------ */

.mobile-nav {
  position: fixed;
  inset: 4.25rem 0 0 0;
  z-index: var(--z-mobile);
  background: var(--bg);
  border-top: 1px solid var(--border);
  overflow-y: auto;
  padding: var(--space-5) var(--gutter) var(--space-8);
}

.mobile-nav__list { display: grid; gap: 0.25rem; }

.mobile-nav__link,
.mobile-nav__heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: 0.9rem 0.4rem;
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--text-strong);
  border-bottom: 1px solid var(--border);
  text-align: left;
}

.mobile-nav__heading .icon { width: 1rem; height: 1rem; color: var(--text-muted); transition: transform var(--duration-base) var(--ease-out); }
.mobile-nav__heading[aria-expanded="true"] .icon { transform: rotate(180deg); }

.mobile-nav__sub { padding: 0.4rem 0 0.8rem 0.4rem; display: grid; gap: 0.15rem; }
.mobile-nav__sub a {
  display: block;
  padding: 0.6rem 0.6rem;
  border-radius: var(--radius-md);
  color: var(--text-muted);
  font-size: var(--text-sm);
}
.mobile-nav__sub a:hover { background: var(--surface); color: var(--text-strong); }

.mobile-nav__actions { margin-top: var(--space-6); }

/* ---- Responsive -------------------------------------------------------------------- */

@media (max-width: 61.99rem) {
  .site-nav { display: none; }
  .site-header__actions .btn { display: none; }
  .nav-burger { display: inline-flex; }
}

@media (min-width: 62rem) {
  .mobile-nav { display: none !important; }
}