.ol-perspective-map {
  position: absolute;
  left: 50%;
  top: 50%;
  width: 200%;
  height: 200%;
  transform: translate(-50%, -50%);
}
.ol-perspective-map .ol-layer {
  z-index: -1!important; /* bug using Chrome ? */
}
.ol-perspective-map .ol-layers {
  transform: translateY(0) perspective(200px) rotateX(0deg) scaleY(1);
}

.ol-perspective-map .ol-overlaycontainer,
.ol-perspective-map .ol-overlaycontainer-stopevent {
  width: 50%!important;
  height: 50%!important;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}