[1, 1];
  var color = [Math.random(), Math.random(), Math.random(), 1];

  drawScene();

  // Setup a ui.
  webglLessonsUI.setupSlider("#x",      {value: translation[0], slide: updatePosition(0), max: gl.canvas.width });
  webglLessonsUI.setupSlider("#y",      {value: translation[1], slide: updatePosition(1), max: gl.canvas.height});
  webglLessonsUI.setupSlider("#angle",  {value: rotationInRadians * 180 / Math.PI | 0, slide: updateAngle, max: 360});
  webglLessonsUI.setupSlider("#scaleX", {value: scale[0],