Editing Openai/692664f7-a230-8000-833c-663a29f9f4d1 (section)

==== - If a Double Move’s first ply delivers checkmate, the game ends immediately (the second ply is not played). ====
* If the first ply puts the opponent in check but does not mate, the moving player still executes the second ply (it is legal to deliver two plys even while the opponent is in check after the first).
* If at any point a player’s king is left in check by an attempted ply, that ply is illegal and cannot be played. During a Double Move the two plys must be legal sequentially; you cannot play a first ply that leaves your king in check and then try to remedy it with the second — the first must be legal by itself.
* Standard draw rules (stalemate, repetition, 50-move rule) apply using the usual definitions — count plys for the 50-move rule as usual (each ply counts).