p.boxed | Pawns start on the 7th rank. Move a knight to promote them. Diagram: ... threatens Nc5-Nd3# and allow 2.b8=Q figure.diagram-container .diagram | fen:: figcaption Standard initial position after 1.Na6 h3 Specifications ul li Chessboard: standard. li Material: standard. li Non-capturing moves: standard. li Special moves: no castling (and no en-passant). li Captures: standard. li End of game: standard. p. ...(Almost) Only the initial position changes, but this is a very big change. In particular, castling would be rather pointless so it's disabled here. En-passant captures are impossible because all pawns already reached 7th rank. h3 Note on initial position p. Since truly random start can allow un-defendable mate in 3 with a knight, the kings touch at least one knight in the initial position. This allows to move free out of potential check from the very beginning. Here is an example: // TODO: diagram figure.diagram-container .diagram | fen:r7/2n5/1q6/5k2/8/8/K7/8: figcaption. The king cannot take on a8 because it's guarded by the knight: it's checkmate h3 Source p | See for example the a(href="https://www.chessvariants.com/diffsetup.dir/upside.html") Upside down chess |  page on chessvariants.com.