/* Full-viewport iframe, no margins or scrollbars */
html,body {
  height:100%;
  margin:0;
  background:#000;
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -ms-user-select: none;
  user-select: none;
  overscroll-behavior: none;
}
iframe#viewer{
  position:fixed;
  inset:0;
  width:100%;
  height:100%;
  border:0;
  display:block;
}