html, body {
  width: 100%;
  height:100%;
  margin: 0;
  padding: 0;
}

#img {
  max-width: 100%;
  max-height: 100%;
}

#overlay {
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
  z-index: 99999999999;
}