Alphabetic Chess: The squares are considered in the order a1, a2…a8, b1…b8, c1 and so on to h8. At each turn, only the unit standing on the square which comes earliest in this order may move. However check and mate are normal.

Circe: Captured units (not Ks) reappear on their game-array squares, of the same colour in the case of pieces, on the file of capture in the case of pawns, and on the promotion square of the file of capture in the case of fairy pieces. If the rebirth square is occupied the capture is normal.

Einstein Chess: All units (Ks excluded) change their type when they move, according to a precise pattern. For non-capture moves: Q>R, R>B, B>S, S>P, P remains P. For capture-moves: R>Q, B>R, S>B, P>S, Q remains Q.

Republican Chess: There are no Kings : if the side which has played can put the opposite King on a square where it would be legally mate, then the opposite King is put on such a square. The opposite side can then put itself the other King on a square where it is mated.

Take & Make: Having captured, a unit must immediately, as part of its move, play a non-capturing move in imitation of the captured unit from the capture-square. If no such move is available, the capture is illegal. Promotion by capture occurs only when a pawn arrives on the promotion rank as the result of a take&make move. Checks are as in normal chess: after the notional capture of the checked K, the checking unit does not move away from the King’s square.

Neutral piece : Belongs to whichever side chooses to use it. It can therefore be moved or captured by White or Black, and in Circe it is reborn according to capture. A King may not be moved onto a square controlled by a neutral piece, because of self-check.