Very nice work!

I noticed a pretty significant bug (i think). The ghost character actually clears the checkpoints for the current rider! As an example, on level two, the rider must go right for checkpoint A, then left for checkpoint B, back to center for the finish. After finishing once, the rider only needs to go left to checkpoint B, then back to the finish. (Checkpoint A is cleared by the ghost rider).

Very impressive all that you've done!