/* ============================================
   Header — Fixed navigation bar
   ============================================ */

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-h);
  background: var(--color-header-bg);
  border-bottom: 1px solid var(--color-border-subtle);
  z-index: var(--z-header);
  backdrop-filter: var(--blur-glass);
  -webkit-backdrop-filter: var(--blur-glass);
}

.site-header__inner {
  max-width: var(--container-max);
  height: 100%;
  margin: 0 auto;
  padding: 0 var(--space-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-6);
}

.site-header__brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-family: var(--font-display);
  font-size: var(--text-md);
  font-weight: 400;
  letter-spacing: 0.18em;
  color: var(--color-text-primary);
  padding-left: var(--space-3);
  border-left: 2px solid rgba(86, 190, 211, 0.5);
}

.site-header__brand img {
  width: 36px;
  height: 36px;
  filter: drop-shadow(0 2px 6px rgba(0, 0, 0, 0.4));
  flex-shrink: 0;
}

.site-header__nav {
  display: flex;
  align-items: center;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: 0;
}

.site-header__nav li {
  position: relative;
}

.site-header__nav li:not(:last-child)::after {
  content: '';
  position: absolute;
  right: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 1px;
  height: 14px;
  background: var(--color-text-dim);
}

.site-header__nav a {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: 0 var(--space-5);
  font-family: var(--font-nav);
  font-size: var(--text-sm);
  font-weight: 400;
  letter-spacing: 0.18em;
  color: var(--color-text-secondary);
  text-transform: uppercase;
  transition: color var(--transition-fast);
}

.site-header__nav a:hover,
.site-header__nav a.is-active {
  color: var(--color-cyan-bright);
}

.site-header__nav a .chevron {
  width: 8px; height: 8px;
  border-right: 1.5px solid currentColor;
  border-bottom: 1.5px solid currentColor;
  transform: translateY(-2px) rotate(45deg);
  transition: transform var(--transition-fast);
}

.site-header__nav li:hover .chevron { transform: translateY(0) rotate(45deg); }

/* ---- Dropdown ---- */
.site-header__dropdown {
  position: absolute;
  top: calc(100% + 0px);
  left: 50%;
  transform: translateX(-50%) translateY(-8px);
  min-width: 200px;
  padding: var(--space-3) 0;
  background: var(--color-header-bg);
  border: 1px solid var(--color-border-subtle);
  border-top: none;
  list-style: none;
  margin: 0;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-base);
  z-index: var(--z-dropdown);
}

.site-header__nav li:hover .site-header__dropdown,
.site-header__nav li:focus-within .site-header__dropdown {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) translateY(0);
}

.site-header__dropdown li::after { display: none; }

.site-header__dropdown a {
  padding: var(--space-3) var(--space-5);
  font-size: var(--text-xs);
  letter-spacing: 0.15em;
  white-space: nowrap;
}

/* ---- Mobile toggle ---- */
.site-header__toggle {
  display: none;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 5px;
  /* iOS Safari renders <button> with default border/background;
     reset so only the three spans are visible. */
  background: transparent;
  border: 0;
  padding: 0;
  cursor: pointer;
  -webkit-appearance: none;
  appearance: none;
}

.site-header__toggle span {
  display: block;
  width: 22px;
  height: 1.5px;
  background: var(--color-text-primary);
  transition: all var(--transition-fast);
}

/* ---- Mobile ---- */
@media (max-width: 900px) {
  .site-header__toggle { display: flex; }

  .site-header__nav {
    position: fixed;
    top: var(--header-h);
    right: 0;
    bottom: 0;
    /* Explicit height: backdrop-filter on .site-header creates a containing
       block, so top/bottom alone collapse to the header's 72px box. */
    height: calc(100vh - var(--header-h));
    height: calc(100dvh - var(--header-h));
    width: 280px;
    background: var(--color-header-bg);
    flex-direction: column;
    align-items: stretch;
    padding: var(--space-6) 0;
    transform: translateX(100%);
    transition: transform var(--transition-base);
    overflow-y: auto;
  }

  .site-header__nav.is-open { transform: translateX(0); }

  .site-header__nav li::after { display: none !important; }

  .site-header__nav a {
    padding: var(--space-4) var(--space-6);
    border-bottom: 1px solid var(--color-border-subtle);
  }

  /* Accordion behavior - dropdowns are collapsed by default on mobile.
     The :hover/:focus-within rules above are overridden here. */
  .site-header__nav li:hover .site-header__dropdown,
  .site-header__nav li:focus-within .site-header__dropdown {
    opacity: 0;
    visibility: hidden;
    transform: none;
  }

  .site-header__dropdown {
    position: static;
    transform: none;
    min-width: 0;
    background: rgba(0, 0, 0, 0.3);
    border: none;
    padding: 0;
    max-height: 0;
    opacity: 0;
    visibility: hidden;
    overflow: hidden;
    transition: max-height var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
  }

  .site-header__nav li.is-expanded > .site-header__dropdown,
  .site-header__nav li.has-dropdown.is-expanded:hover > .site-header__dropdown {
    max-height: 500px;
    opacity: 1;
    visibility: visible;
  }

  .site-header__dropdown a {
    padding-left: var(--space-10);
    font-size: var(--text-xs);
  }

  .site-header__nav li.has-dropdown > a {
    cursor: pointer;
    position: relative;
  }

  .site-header__nav li.has-dropdown > a .chevron {
    transition: transform var(--transition-base);
  }

  .site-header__nav li.has-dropdown.is-expanded > a .chevron {
    transform: translateY(0) rotate(-135deg);
  }
}