This is my biggest project (so far): Autorennen / Car Race.
See the notes for English translations. There is a bug with Snap!, you can't use it in fullscreen mode. 
nice game! thank you for sharing. Oh, it works fine in presentation- / fullscreen mode on my retina display! (Maybe the recent fix to pixel-perfect collision detection also improved that behavior, because your sensors are so tiny). It would be interesting to do this without color collision detection by using nested sprites for sensors!