.overlay {  
    position:absolute;
    top:0;
    left:0;
    width:100%;
    height:100%;
    z-index:1000;
    background-color:grey;
    opacity: .8;
  }

  #qr-reader{
    position:absolute;
    width:100vw;
    left:0px;
    top:0px;
  }

  #zoominbox{
    display:none;
    position:absolute;
    right:4vw;
    top:4vw;
    width:14vw;
    height:14vw;
    font-size:14vw;
    z-index:500;
    color:greenyellow;
  }
  #zoomoutbox{
    display:none;
    position:absolute;
    left:4vw;
    top:4vw;
    width:14vw;
    height:14vw;
    font-size:14vw;
    z-index:500;
    color:orange;
  }
  .greyout{
    color:grey !important;
  }