#loading {
  /* (A1) COVER FULL PAGE */
  position: fixed;
  top: 0; left: 0; z-index: 999;
  width: 100vw; height: 100vh;

  /* (A2) SPINNER IMAGE */
  background-color: black;
  background-image: url("ajax-loader.gif");
  background-position: center;
  background-repeat: no-repeat;
}