.video-background {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  overflow: hidden;
  pointer-events: none; /* stops video from blocking clicks on your page */
}

.video-background iframe {
  width: 100vw;
  height: 56.25vw;   /* 16:9 ratio */
  min-height: 100vh;
  min-width: 177.77vh;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}