anchor.diff:      _gl.uniformMatrix3fv(_uIdentMatrix, false, identMatrix.storage);
     }
   
  -  bool render(double time) {
  +  void render(double time) {
       _gl.viewport(0, 0, _viewportWidth, _viewportHeight);
       _gl.clear(webgl.RenderingContext.COLOR_BUFFER_BIT | webgl.RenderingContext.DEPTH_BUFFER_BIT);
   
  
positive.code:     _viewportHeight = height;
    }
  
    Lesson07(CanvasElement canvas) {
      window.onResize.listen((e){
        resize(canvas, e.currentTarget.innerWidth, e.currentTarget.innerHeight);
      });
  
negative.code: }
  
  void main() {
    TwoBarrels tb = new TwoBarrels(document.querySelector('#game'));
    tb.start();
  }
  