/* ==========================================================================
   Section 01 — Site header
   Fixed navigation. Transparent while it sits over the navy hero, then it
   solidifies on scroll so it stays readable over the light sections.
   ========================================================================== */

.site-header {
  position: fixed;
  inset: 0 0 auto;
  z-index: var(--z-header);
  background-color: transparent;
  transition: background-color var(--dur) var(--ease),
              box-shadow var(--dur) var(--ease);
}

.site-header.is-stuck {
  background-color: var(--c-navy);
  box-shadow: var(--sh-header);
}

/* On pages that are NOT the front page (posts, archives, etc.), the header
   must start solid because there is no dark hero behind it. */
body:not(.home) .site-header {
  background-color: var(--c-navy);
  box-shadow: var(--sh-header);
}

.site-header__inner {
  display: flex;
  align-items: center;
  gap: var(--sp-6);
  min-height: var(--header-h);
}

.site-header__logo {
  flex: none;
  margin-right: auto;
}

.site-header__logo img {
  width: auto;
  height: clamp(38px, 3.2vw, 48px);
}

/* --- Navigation ----------------------------------------------------------- */

.nav {
  display: flex;
  align-items: center;
  gap: clamp(var(--sp-5), 2.6vw, var(--sp-9));
}

.nav__link {
  position: relative;
  color: var(--c-on-dark);
  font-size: var(--fs-body);
  font-weight: var(--fw-medium);
  transition: color var(--dur) var(--ease);
}

.nav__link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -6px;
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background-color: var(--c-blue-bright);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur) var(--ease);
}

.nav__link:hover,
.nav__link[aria-current="true"] {
  color: var(--c-sky);
}

.nav__link:hover::after,
.nav__link[aria-current="true"]::after {
  transform: scaleX(1);
}

.site-header .btn {
  flex: none;
  min-height: 48px;
  padding-inline: var(--sp-6);
}

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

.nav-toggle {
  display: none;
  place-items: center;
  width: 46px;
  height: 46px;
  margin-left: auto;
  border-radius: var(--r-sm);
  color: var(--c-on-dark);
}

.nav-toggle__bars {
  position: relative;
  display: block;
  width: 24px;
  height: 2px;
  border-radius: 2px;
  background-color: currentColor;
  transition: background-color var(--dur) var(--ease);
}

.nav-toggle__bars::before,
.nav-toggle__bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 24px;
  height: 2px;
  border-radius: 2px;
  background-color: currentColor;
  transition: transform var(--dur) var(--ease);
}

.nav-toggle__bars::before {
  top: -7px;
}

.nav-toggle__bars::after {
  top: 7px;
}

/* Burger morphs into a cross while the drawer is open. */
.nav-toggle[aria-expanded="true"] .nav-toggle__bars {
  background-color: transparent;
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bars::before {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bars::after {
  transform: translateY(-7px) rotate(-45deg);
}

/* --- Breakpoint ----------------------------------------------------------- */

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

  .nav {
    position: fixed;
    inset: var(--header-h) 0 auto;
    z-index: var(--z-drawer);
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: var(--sp-4) var(--container-pad) var(--sp-7);
    background-color: var(--c-navy);
    box-shadow: var(--sh-header);
    /* Collapsed by default; the toggle flips the data attribute. */
    visibility: hidden;
    opacity: 0;
    transform: translateY(-12px);
    transition: opacity var(--dur) var(--ease),
                transform var(--dur) var(--ease),
                visibility var(--dur) var(--ease);
  }

  .nav[data-open="true"] {
    visibility: visible;
    opacity: 1;
    transform: none;
  }

  .nav__link {
    padding-block: var(--sp-4);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 1.125rem;
  }

  .nav__link::after {
    display: none;
  }

  .nav .btn {
    margin-top: var(--sp-5);
    width: 100%;
  }
}