#overlay {
  position: fixed;
  top: 0;
  left: 0;
  opacity: 1;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,.75);
  transition: opacity 300ms;
  z-index: 500;
}

#overlay.hide {
  pointer-events: none;
  opacity: 0;
}