/* ==========================================================================
   Site header, navigation, language switch, theme toggle
   ========================================================================== */

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--color-bg) 88%, transparent);
  backdrop-filter: saturate(160%) blur(10px);
  -webkit-backdrop-filter: saturate(160%) blur(10px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--dur-fast) ease;
}
.site-header.is-scrolled {
  border-bottom-color: var(--color-border);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  min-height: 4.25rem;
}

/* Brand */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
  text-decoration: none;
  color: var(--color-text);
  min-height: 2.75rem;
}
.brand__mark {
  color: var(--color-brand);
  width: 2rem;
  height: 2rem;
}
:root[data-theme='dark'] .brand__mark {
  color: var(--color-accent);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme='light']) .brand__mark {
    color: var(--color-accent);
  }
}
.brand__text {
  display: flex;
  flex-direction: column;
  line-height: 1.1;
}
.brand__name {
  font-weight: 800;
  letter-spacing: var(--tracking-tight);
  font-size: 1.05rem;
  white-space: nowrap;
}
.brand__role {
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: var(--tracking-wide);
  text-transform: uppercase;
  color: var(--color-text-faint);
}

/* Navigation (desktop) */
.site-nav {
  display: flex;
  align-items: center;
  gap: var(--space-5);
}
.site-nav__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  align-items: center;
  gap: var(--space-1);
}
.site-nav__link {
  display: inline-flex;
  align-items: center;
  min-height: 2.75rem;
  padding: 0.4rem 0.7rem;
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-muted);
  text-decoration: none;
  position: relative;
  white-space: nowrap;
}
.site-nav__link:hover {
  color: var(--color-text);
  background: var(--color-surface-2);
}
.site-nav__link.is-active {
  color: var(--color-text);
}
.site-nav__link.is-active::after {
  content: '';
  position: absolute;
  left: 0.7rem;
  right: 0.7rem;
  bottom: 0.3rem;
  height: 2px;
  background: var(--color-accent);
  border-radius: 2px;
}
.site-nav__tools {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

/* Language switch */
.lang-switch__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: inline-flex;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  overflow: hidden;
}
.lang-switch__item {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 2.5rem;
  min-height: 2.25rem;
  padding: 0 0.5rem;
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
  text-decoration: none;
  border-right: 1px solid var(--color-border);
}
.lang-switch__list li:last-child .lang-switch__item {
  border-right: 0;
}
a.lang-switch__item:hover {
  background: var(--color-surface-2);
  color: var(--color-text);
}
.lang-switch__item.is-current {
  background: var(--color-brand);
  color: var(--color-on-brand);
}
:root[data-theme='dark'] .lang-switch__item.is-current {
  background: var(--color-accent);
  color: #06201d;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme='light']) .lang-switch__item.is-current {
    background: var(--color-accent);
    color: #06201d;
  }
}

/* Theme toggle */
.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.75rem;
  height: 2.75rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  color: var(--color-text-muted);
}
.theme-toggle:hover {
  color: var(--color-text);
  border-color: var(--color-border-strong);
}
.theme-toggle__icon {
  display: none;
  line-height: 0;
}
.theme-toggle__icon--dark {
  display: inline-flex;
}
:root[data-theme='dark'] .theme-toggle__icon--dark {
  display: none;
}
:root[data-theme='dark'] .theme-toggle__icon--light {
  display: inline-flex;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme='light']) .theme-toggle__icon--dark {
    display: none;
  }
  :root:not([data-theme='light']) .theme-toggle__icon--light {
    display: inline-flex;
  }
}

/* Mobile toggle */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 0.6rem;
  min-height: 2.75rem;
  padding: 0.4rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  font-size: var(--text-sm);
  font-weight: 700;
}
.nav-toggle__icon {
  position: relative;
  width: 1.1rem;
  height: 0.875rem;
  display: inline-block;
}
.nav-toggle__bar {
  position: absolute;
  left: 0;
  width: 100%;
  height: 2px;
  background: currentColor;
  border-radius: 2px;
  transition:
    transform var(--dur) var(--ease-out),
    opacity var(--dur-fast) ease;
}
.nav-toggle__bar:nth-child(1) {
  top: 0;
}
.nav-toggle__bar:nth-child(2) {
  top: 6px;
}
.nav-toggle__bar:nth-child(3) {
  top: 12px;
}
.nav-toggle[aria-expanded='true'] .nav-toggle__bar:nth-child(1) {
  transform: translateY(6px) 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(-6px) rotate(-45deg);
}

@media (max-width: 64rem) {
  .site-nav__cta {
    display: none;
  }
  .site-nav {
    gap: var(--space-3);
  }
  .site-nav__link {
    padding-inline: 0.5rem;
  }
}

@media (max-width: 56rem) {
  .nav-toggle {
    display: inline-flex;
  }
  .site-nav {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: var(--space-4);
    padding: var(--space-4) var(--gutter) var(--space-6);
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow);
    max-height: calc(100dvh - 4.25rem);
    overflow-y: auto;
  }
  .site-nav.is-open {
    display: flex;
  }
  .site-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }
  .site-nav__link {
    display: flex;
    min-height: 3rem;
    font-size: var(--text-base);
    padding-inline: var(--space-2);
    border-bottom: 1px solid var(--color-border);
    border-radius: 0;
  }
  .site-nav__link.is-active::after {
    display: none;
  }
  .site-nav__link.is-active {
    color: var(--color-accent-text);
  }
  .site-nav__tools {
    flex-wrap: wrap;
    justify-content: space-between;
  }
  .site-nav__cta {
    display: inline-flex;
    width: 100%;
    min-height: 3rem;
    font-size: var(--text-sm);
  }
  .brand__role {
    display: none;
  }
}