.video-area {
  width: 400vw;
  height: 600vh;
  position: fixed;
  top: 0;
  left: 0;
  z-index: -1;
}

@media screen and (min-width:1920px) {
   video {width: 100%}
 }
@media screen and (max-width:768px) {
  video {width: 100%}
}