#interactive {
    position: relative;
    width: 640px;
    height: 480px;
  }
  
  #interactive video {
    width: 100%;
    height: 100%;
    display: block;
  }
  
  .drawingBuffer {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
  }