.overlay {
  position: fixed;
  top: 0;
  right: 0;
  left: 0;
  bottom: 0;
  z-index: 1;
  visibility: hidden;
  opacity: 0;
  transition: opacity 200ms ease-in-out 200ms;
  overflow: hidden;
}
.open .overlay {
  visibility: visible;
  opacity: 1;
}
.overlay.overlay--black {
  background-color: rgba(0, 0, 0, 0.4);
}