The Pulsar Chess program offers regular chess and three chess variants: crazyhouse chess, loser's chess, and atomic chess. Additional variants of three checks and giveaway can be purchased within the app from the game menu.
Pulsar features multiple levels of play from beginner to advanced and includes the rules of all its games. The game button - new game menu item, lets the user control the variant and difficulty. In the new game view if play against Pulsar is set to off the board can be used for a two person game against some one physically present as a way to enforce legality, clocks, and results in an over the board variant game. This is the same Pulsar Chess program that i've developed for computers.