One more little thing. I'm not completly sure about this.

I think that the Transform should only be computed if the Group it will actually going to use the ShapeRenderer, something like this:

```java
			// attempt to draw self
			if (g instanceof ShapeDrawable) {
				sr.setTransformMatrix(getGroupTransform(g));
				ShapeDrawable sd = (ShapeDrawable) g;
				sd.drawShapes(sr);
			}
```