Brad Stone mentioned this game in an email to me, and helped me clarifying certain unclarities in the rules, as taken from Pritchard's Encyclopedia of Chess Variants. This game was invented by Bruce Harper and Duncan Suttles, in the 1960's. Brad learned this game in a wargaming convention in Ottawa, Canada, during the early 70s. Pritchard writes that this game has been played from Vancouver to Nova Scottia, also in Germany, but probably not often.
The game is played on an 8 by 8 board, with four extra squares, adjacent to d1, e1, d8, and e8. Alternatively, one can play the game on a usual chessboard, and just `remember that these squares are there': as they have a special role, they will not be used for `normal play'.
Each player has the normal set of pieces. However, pieces have different names, and one rook is inverted. The initial setup is the following:
White: Immobilizer (King) e1, Bomb (Queen) d1, Tank (Rook) h1, Imitiator (inverted Rook) a1, Detonators (Knights) b1, g1, Super-Twekes (Bishops) b2, g2, Twekes (Pawns) c2, c3, d2, d3, e2, e3, f2, f3. Blacks setup is mirrored with Immobilizer on e8 and Bomb on d8.
The Twekes move as chess-kings, but can also leap like men in draughts or checkers, but in all directions (horizontal, vertical, diagonal): when leaping it moves two squares in any direction; the square `leaped over' should be occupied by some piece, and the square moved to should be empty. When twekes move over enemy pieces, these are taken, but when a tweke moves over an enemy bomb, the bomb is not taken or detonated. As in draughts, twekes may make more than one successive jump in the same turn, changing directions. Twekes cannot jump over friendly pieces and enemy pieces in the same turn. Twekes are represented by pawns.
The Super-twekes move in the same way as twekes, but may also jump over friendly pieces and enemy pieces in the same turn. Super-twekes are represented by bishops.
The Immobilizer moves as a super-tweke, but enemy pieces jumped over are not taken. Immobilisers do not take pieces. Instead, any enemy piece that stands adjacent to an immobiliser can not be moved. The immobiliser is represented by the king.
The Bomb moves like a chess-king. It cannot capture, and it also cannot be captured. A player may detonate the bomb in a move, either after making a move with the bomb or instead of making a normal move. The effect of this detonation is that the bomb and all pieces with distance at most 2 to the bomb are removed from the board: when a bomb is detonated in the middle of the board, all pieces on an square area of five by five squares are removed (this could include an enemy bomb). When one of the pieces so taken is another bomb, this bomb also detonates, thus possibly removing even more pieces from the board. Pieces in the `extra squares' are not removed. The bomb is represented by the queen.
The Tank moves like a chess-king. Tanks do not jump, and do not capture other pieces. Instead, it pushes pieces adjacent to it in the direction the tank moves. A piece pushed off the board is lost; however, a bomb explodes before it is pushed off the board. The tank is represented by a rook.
The Imitiator moves and takes in the same way as the last enemy piece that has moved. For instance, if the last move of the opponent was with an immobiliser, the player can move the imitator and freeze pieces of the opponent, which are frozen until the imitator moves again. (Note that imitating a bomb also belongs to the possibilities, which gives interesting possibilities.) The imitator is represented by a rook, that is turned around and placed on its head.
The Detonators move in the same way as the immobilisers, i.e., as a bishop with leaps. A detonator can detonate the enemy bomb by moving to the square with this bomb on it. Also, when a player has two detonators, all pieces on the so-called `co-squares' are removed from play. (The co-squares of two squares are those that together with the first two form the four corners of a rectangle. For instance, the co-squares of b3 and e6 are b6 and e3. Hence, when a player has a detonator on b2, and moves a denotator to g5, all pieces that are on b5 and/or g2 are taken.) Also, bombs on co-squares are detonated. The detonators are represented by knights.
Instead of moving, a player may remove one of his own pieces that can not move from the board.
Object of the game is two move two pieces to the two extra squares at the opponents side of the board. Pieces of a player may not be located at the two extra squares at his own side of the board (e.g., a piece pushed to such a square by a tank is considered to be pushed from the board.)
Bombs are important pieces: bombs going off can destroy many pieces, of yourself, or, better, of your enemy. Also, as an imitator can imitate a bomb, effectually, three, or possibly even four bombs can go off at about the same time, possibly wiping out most of the pieces.
The twekes and super-twekes can lead to wild and unexpected moves, because of their great jumping abilities.