Going off one edge brings you back on the opposite side.
How to play
The board is a donut (torus): 8 files by 12 ranks, and every piece that slides off the left edge reappears on the right, and off the top reappears at the bottom. Each army has two pawn walls: one facing the enemy directly and one facing it "around the back" across the seam (the shaded ranks 9-12). Pawns of both walls promote to a queen on the enemy back rank. Pieces move as in chess but along wrapped lines; there is no castling or en passant. Checkmate the enemy king to win; stalemate is a draw.