html,
body {
  margin: 0;
  padding: 0;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  background: #000;
  text-align:center;
  color:#fff;
}

#holder{
    height:100%;
    width:100%;
    
}

#cnv{
    height:100vh;
    width:100vw;
}

#code{
    text-align:center;
    
    background-color: rgba(0,0,0,0.5);
    color: #fff;
   
    font-size:2em;
    left:calc(50%-200px);
    top:50vh;
    width:400px;
}

#codeholder{
    text-align:center;
    position : absolute;
    z-index:10;
    left:0;
    top:50vh;
    width:100%;
}