Chess games may be a dime a dozen, and $7.99 may seem like a lot to ask, but t Chess Pro is arguably the best, with its human-like challenge algorithms and ELO rating support (a way of calculating relative player abilities) of between 500 and 2,500. In addition to its ‘Retina’-ready 2D and ray-traced 3D views, the game is “buy-once, use-anywhere,” so if you’re also an iPhone user, you can pull it down on either platform without purchasing it twice. [App Store]