Is there an existing ruleset for chess where you keep playing all the way to one remaining piece? Something like this: The normal rules for check and mate apply, except on mate the king has to be taken and then play continues like normal. Instead of stalling out with a stalemate for too many moves without a capture, shrink the board by one tile on every side, moving pieces inward if necessary, and keep playing. If a player has no legal moves, he can upgrade one piece to the next more valuable piece in order to move. Last man standing wins.