Millennium 3D chess

Millennium 3D chess is a three-dimensional chess variant created by William L. D'Agostino in 2001. It is played on three vertically stacked 8×8 boards, numbered levels 1, 2 and 3, with the white army starting in standard formation on board 1 and the black army on board 3, each player commanding an ordinary set of chess pieces. Every piece moves exactly as in chess within its own board and gains extra movement between boards: the king may step one level up or down, the knight shifts one board and two squares or two boards and one square, the bishop and rook gain vertical and combined moves, and the queen combines the two. Pawns can move vertically, may open with a two-step move, and promote on the opponent's back rank and starting board. Moves are recorded in algebraic notation with the level number before each square. D'Agostino says his aim was to extend the traditional game into a multilevel environment without distorting the basic game. The variant is documented in The Classified Encyclopedia of Chess Variants.