body {
  padding: 0;
  margin: 0;
  background: #000;
  color: #fff;
  overflow: hidden;

  user-select:none;
  -webkit-tap-highlight-color:rgba(0,0,0,0);
}

canvas {
  width: 100%;
  height: 100%;
}
body {
  padding: 0;
  margin: 0;
  background: #000;
  color: #fff;
  overflow: hidden;

  user-select:none;
  -webkit-tap-highlight-color:rgba(0,0,0,0);
}

canvas {
  width: 100%;
  height: 100%;
}

@media (max-width: 759px) {
  #toggleFullScreenBtn {
    position: absolute;
    font-size: 40px;
    line-height: 120px;
    width: 50vw;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
  }
}

Enlarge fullscreen btn on mobile
Enlarge fullscreen btn on mobile
