#particles-js {
  width: 100%;
  height: 100%;
  background-image: url('');
  background-size: cover;
  background-position: 50% 50%;
  background-repeat: no-repeat;
  position:absolute;
  top:0;
  bottom: 0;
  left:0;
  right:0;
  z-index:0;
}