.site-header {
  position:fixed;
  top:0;
  width:100%;
  padding:1rem 2rem;
  display:flex;
  justify-content:space-between;
  align-items:center;
  background:transparent;
  z-index:1000;
  transition:all .3s ease;
}
.site-header.scrolled {
  background:rgba(255,255,255,.75);
  backdrop-filter:blur(12px);
}