Pretty environments, but sometimes the obstacles get lost until I've hit my boomerang against them. Maybe another colour would be better, but that could compromise the nice visuals as well. Also cool dynamic lighting. Like the presentation in general, and while the boomerang is a bit difficult to control, it displays every info you need to do so. So it is mostly a matter of practice.
I am purely ideaguying here, without the full knowledge of the implementation difficulties it involves. But maybe an invisible "highlight field" surrounding the boomerang that will light up the inside of the obstacles depending on how close the boomerang is at the moment. The yellow part is invisible.