html, body {
  height: 100%;
  margin: 0;
  padding: 0;
  width: 100%;
  overflow: hidden;
}
iframe {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  border: none;
  margin: 0;
  padding: 0;
  z-index: 1;
  display: block;
}
#overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: rgba(0,0,0,0.7);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  z-index: 10;
  cursor: pointer;
  user-select: none;
  transition: opacity 0.5s;
}
#overlay.hide {
  opacity: 0;
  pointer-events: none;
}