Special Moves
Promotions
A Promotion is a transformation of a man to a piece. Promotion occurs when a Pawn moves to a cube in y = 8, relative to the player. The pawn would then be promoted to a piece, except a king, of the player's choice. It also occurs when a King is taken. In this case, the Prince to be promoted to King is chosen by the owner of the King.
Double-Cube Advance
The pawn can move forward two cubes, assuming that it has not moved. Initially, 2D Chess did not have the pawn's double-square advance rule. It was added later to stimulate the game's opening. I have decided to keep this rule, however worthless, because of one of my Postulates.
En Passant
Immediately following a Double-Cube Advance, a player may counter-attack with this move. To do this, the player must have a Pawn exactly one cube left, right, up, or down from the pawn that just executed the Double-Cube Advance. The player's pawn moves to where the opposing pawn would have been, if it had moved only one cube forward and the opposing pawn is removed.
Castling
Castling is a powerful, unique move because it requires two pieces. If one castles, one moves one's King two cubes towards one's Rook and moves one's Rook in the opposite direction, placing it adjacent to one's King. To Castle, there must be a clear path between the King and the Rook. Also, both pieces must not have moves previously. Castling cannot get a King out of Check even though a King can Castle while in Check, if there is at least one prince. If this happens, the opponent can move to the King's previous cube and remove the King. If a King Castles, the opponent could move to where the Rook is and remove both the King and the Rook, but only on the following turn.