body {
  margin: 0;
}

@media (min-aspect-ratio: 16/9) {
  .video iframe {
    height: 56.25vw;
    width: 100vw;
  }
}
@media (max-aspect-ratio: 16/9) {
  .video iframe {
    width: 177.78vh;
    height: 100vh;
  }
}
div.video {
  z-index: -99;
  position: absolute;
  overflow: hidden;
  width: 100vw;
  height: 100vh;
  margin: 0;
}
div.video iframe {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  margin: 0;
}