.site-header {
  position: fixed;
  transition: background-color .28s ease, color .28s ease, box-shadow .28s ease;
}

.brand {
  position: relative;
  display: block;
  width: 190px;
  aspect-ratio: 1669 / 543;
}

.brand img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: contain;
  transition: opacity .2s ease;
}

.brand .logo-on-light { opacity: 0; }

.site-header.scrolled {
  background: rgba(251, 250, 246, .96);
  color: var(--green);
  box-shadow: 0 1px 0 var(--line);
  backdrop-filter: blur(12px);
}

.site-header.scrolled .logo-on-dark { opacity: 0; }
.site-header.scrolled .logo-on-light { opacity: 1; }
.site-header.scrolled .nav-cta { border-color: var(--green); }
.site-header.scrolled .menu-toggle span { background: var(--green); }

@media (max-width: 640px) {
  .brand { width: 156px; }
  .site-header nav.open { color: white; }
}