Pieces that leave the board reappear on the opposite side.
Borderless chess starts from the same position as standard chess, but the board wraps horizontally without limit: a piece that moves off the left or right edge reappears on the opposite side, for every piece type including a pawn's forward move. Vertically the wrap only goes one way per side — each army can advance off its far edge, but can't retreat back through its own home rank. Familiar opening theory stops applying fast. Play solo against the AI or challenge a friend online — check and checkmate are unchanged.