-After a piece has been taken, the following team must also immediately take a piece or their opponent can move the opposing king one square in any direction. A king cannot be moved into check in this manner, nor does it prevent a king from castling if it ever finds itself back in its start position without having been conventionally "moved".
i.e. if black takes a piece, then white must immediately take a piece or black can move white's king one square in any direction on their next turn.
Pawns may move backward as well as forward. They may not take or check backward. They promote on the enemy's back line as normal.
Not sure how to do the board yet. Anyone out there with Photoshop skills who can be the boardkeeper?