.video {
  height: 0;
  overflow: hidden;
  padding-bottom: 56.25%;
  position: relative;
  width: 100%;
}
.video > iframe,
.video > video {
  bottom: 0;
  height: 100%;
  left: 0;
  position: absolute;
  right: 0;
  top: 0;
  width: 100%;
}