Hyperchess

From the manufacturer:

Hyperchess is an intriguing extension of chess into the third dimension. It is, so far as we know, the first and only playable form of chess in three dimensions. A number of attempts have been made over the years to extend chess into three dimensions, but in one way or another each has suffered some flaw that has compromised the integrity of the basic game, and therefore none has been generally accepted. We feel that Hyperchess overcomes these problems and is for the first time a viable three-dimensional version of chess.

The regular rules of chess apply in Hyperchess, and the object of the game remains the same--to checkmate the opponent's king. In addition, the game is played on the same number of board squares as traditional chess, with the same number of chessmen who keep their same moves. The dramatic difference is, of course, that play is extended into the next dimension. Each chessman may move vertically as well as horizontally. This opens up exciting new possibilities for the world's oldest and most popular game.