To race on a track that is the mirror image of the normal one, after the start of the race, turn around. On the normal tracks this must be before you get onto the main straight. On the extra courses this must be before you get the first bend. Now accelerate as fast as possible and drive through the brick wall in front of you. You'll now be able to carry on around the track, but what was a right hand turn will have become a left one and what was a left turn, will have become right. Novel, eh?