/* The only rule that matters */
#video-background {
/*  making the video fullscreen  */
  position: fixed;
  right: 0; 
  bottom: 0;
  min-width: 100%; 
  min-height: 100%;
  width: auto; 
  height: auto;
  z-index: -100;
}

/* 
https://codepen.io/mattgrosswork/pen/jrdwK
*/