They are random. There is a one in four chance of one of them appearing each time the dots spawn. Perhaps I should have structured it better and maybe thats something to do in an update after the jam is over. When we were play testing we found that this felt about right. Any more and they would spawn too often and on later levels you were running around the track so fast that power orbs would spawn at a rate where you were essentially always invincible. Theres a tricky balance there but I think we can find it. Thanks for your feedback :)