#iframe_curtain {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
  margin: 0;
  padding: 0;
  opacity: 0;
  pointer-events: none;
}

#iframe_curtain.visible {
  pointer-events: auto;
  z-index: 1001;
}