/* ==========================================================================
   Header & Navigation — CSI Dry Eye
   ========================================================================== */

/* ---- Header shell ---- */

.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: var(--z-header);
  transition: background-color 0.3s ease,
              box-shadow 0.3s ease;
}

/* Transparent state (over hero) */
.header--transparent {
  background-color: transparent;
}

.header--transparent .header__nav-link {
  color: var(--color-text-inverse);
}

.header--transparent .header__nav-link:hover {
  color: var(--color-accent);
}

/* Scrolled state */
.header--transparent.header--scrolled {
  background-color: rgba(255, 255, 255, 0.98);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: 0 1px 8px rgba(0, 0, 0, 0.06);
}

.header--scrolled .header__nav-link {
  color: var(--color-text);
}

.header--scrolled .header__nav-link:hover {
  color: var(--color-primary);
}

/* Non-transparent (sub-pages without hero) */
.header:not(.header--transparent) {
  background-color: var(--color-bg);
  box-shadow: 0 1px 8px rgba(0, 0, 0, 0.06);
}

/* ---- Inner layout ---- */

.header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
  max-width: 1200px;
  margin-inline: auto;
  padding-inline: var(--space-lg);
}

/* ---- Logo ---- */

.header__logo img {
  height: 48px;
  width: auto;
}

/* White logo visible on dark/transparent header, hidden when scrolled */
.header__logo-white {
  display: none;
}

.header__logo-color {
  display: block;
}

.header--transparent .header__logo-white {
  display: block;
}

.header--transparent .header__logo-color {
  display: none;
}

/* When scrolled, swap back to color logo */
.header--transparent.header--scrolled .header__logo-white {
  display: none;
}

.header--transparent.header--scrolled .header__logo-color {
  display: block;
}

/* ---- Desktop nav ---- */

.header__nav {
  display: none;
  align-items: center;
  gap: var(--space-2xl);
}

@media (min-width: 1024px) {
  .header__nav {
    display: flex;
  }
}

.header__nav-link {
  font-size: var(--fs-sm);
  font-weight: var(--fw-semibold);
  text-decoration: none;
  color: var(--color-text);
  background: none;
  border: none;
  cursor: pointer;
  font-family: inherit;
  transition: color var(--transition-fast);
}

.header__nav-list {
  display: flex;
  align-items: center;
  gap: var(--space-2xl);
  list-style: none;
  margin: 0;
  padding: 0;
}

.header__nav-item {
  position: relative;
}

/* ---- Dropdowns ---- */

.header__nav-item--dropdown {
  position: relative;
}

.header__dropdown-toggle {
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.header__dropdown-arrow {
  width: 12px;
  height: 12px;
  transition: transform var(--transition-fast);
}

.header__nav-item--dropdown.open .header__dropdown-arrow {
  transform: rotate(180deg);
}

.header__dropdown {
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%) translateY(8px);
  min-width: 220px;
  background-color: var(--color-bg);
  border-radius: var(--radius-lg);
  padding: var(--space-sm);
  box-shadow: var(--shadow-lg);
  opacity: 0;
  pointer-events: none;
  list-style: none;
  transition: opacity var(--transition-base),
              transform var(--transition-base);
}

/* Invisible bridge to prevent hover gap */
.header__dropdown::before {
  content: "";
  position: absolute;
  top: -8px;
  left: 0;
  width: 100%;
  height: 8px;
}

.header__nav-item--dropdown.open .header__dropdown {
  opacity: 1;
  pointer-events: auto;
  transform: translateX(-50%) translateY(0);
}

.header__dropdown-link {
  display: block;
  padding: var(--space-sm) var(--space-lg);
  border-radius: var(--radius-md);
  font-size: var(--fs-sm);
  color: var(--color-text);
  text-decoration: none;
  transition: background-color var(--transition-fast);
}

.header__dropdown-link:hover {
  background-color: var(--color-bg-light);
  text-decoration: none;
}

.header__dropdown-separator {
  height: 1px;
  background-color: var(--color-border-light);
  margin: var(--space-xs) var(--space-lg);
}

/* ---- Header actions (CTA buttons) ---- */

.header__actions {
  display: none;
  align-items: center;
  gap: var(--space-sm);
}

@media (min-width: 1024px) {
  .header__actions {
    display: flex;
  }
}

/* Log In button transparent state */
.header--transparent .header__actions .btn--outline {
  border-color: rgba(255, 255, 255, 0.4);
  color: rgba(255, 255, 255, 0.85);
}

.header--transparent .header__actions .btn--outline:hover {
  background-color: rgba(255, 255, 255, 0.1);
  color: #fff;
  border-color: rgba(255, 255, 255, 0.7);
}

.header--transparent.header--scrolled .header__actions .btn--outline {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.header--transparent.header--scrolled .header__actions .btn--outline:hover {
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
}

/* ---- Mobile toggle ---- */

.header__mobile-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  background: none;
  border: none;
  cursor: pointer;
}

@media (max-width: 1023px) {
  .header__mobile-toggle {
    display: flex;
  }
}

.header--transparent .header__mobile-toggle {
  color: var(--color-text-inverse);
}

.header--scrolled .header__mobile-toggle {
  color: var(--color-text);
}

.header:not(.header--transparent) .header__mobile-toggle {
  color: var(--color-text);
}

/* Hamburger icon */
.header__hamburger {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 22px;
  height: 18px;
}

.header__hamburger span {
  display: block;
  width: 100%;
  height: 2px;
  background-color: currentColor;
  border-radius: 1px;
  transition: transform 0.3s ease, opacity 0.3s ease;
}

/* ---- Mobile menu ---- */

.mobile-menu {
  position: fixed;
  inset: 0;
  z-index: var(--z-mobile);
  background-color: var(--color-bg-navy);
  display: flex;
  flex-direction: column;
  padding: var(--space-2xl) var(--space-lg);
  transform: translateX(100%);
  transition: transform 0.35s ease;
}

.mobile-menu--open {
  transform: translateX(0);
}

.mobile-menu__close {
  position: absolute;
  top: var(--space-md);
  right: var(--space-md);
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-inverse);
  background: none;
  border: none;
  cursor: pointer;
}

.mobile-menu__nav {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
  margin-top: var(--space-3xl);
}

.mobile-menu__link {
  display: block;
  padding: var(--space-md);
  font-size: var(--fs-lg);
  font-weight: var(--fw-semibold);
  color: var(--color-text-inverse);
  text-decoration: none;
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast);
}

.mobile-menu__link:hover {
  background-color: rgba(255, 255, 255, 0.05);
  text-decoration: none;
}

.mobile-menu__actions {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  margin-top: auto;
  padding-top: var(--space-xl);
}