Crazyhouse is a two-player version of Bughouse. In Bughouse, four people, divided into two teams, play two Chess games. Members of the same team play different games, with one playing Black and one playing White. Whenever a player captures a piece, he gives it to his teammate, who may hold it in hand and drop it into his own game on a subsequent turn. In Crazyhouse, a player gives captured pieces to himself, changing their color, so that they now belong to his side. This makes Crazyhouse a bit less crazy than Bughouse. Crazyhouse is very similar to Chessgi, whose origins are in Shogi rather than Bughouse, but a couple of the rules are different. In Crazyhouse, Pawns may not be dropped on the first or last rank, and promoted Pawns turn back into Pawns when they are captured.
 
The ZRF gives you the option of four different piece sets. These include the motif set pictured below, the magnetic set I included with Magnetic Chess, the abstract set pictured with Mortal Chessgi, and the default Zillions set.
 
For more games by Fergus Duniho, goto http://www.duniho.com/fergus/games