If you want an incredibly fun game to play on your Mac, go and buy And Yet It Moves from the Mac App Store. I've been playing it for the last day and it's one of the best games I've played on my Mac in years.
In And Yet It Moves you play a character who has to navigate his way around seventeen levels of ecological wonder by running and jumping -- and rotating the world around him. Turn walls into floors, tilt the world to make an uncrossable bottomless pit into nothing more than a minor inconvenience, and rotate the world until you've shuffled drops of water through a maze to help your erode through the earth to reach the next level. With a ninety degree rotation of the world, a large rolling bolder that's about to crush
