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

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* A ply = a single side’s move (White’s single move or Black’s single move).
* A turn in SDM Chess normally equals 1 ply for the player whose side it is. A Double Move = 2 consecutive plys played by the same side during that side’s turn.

==== - On your normal turn you may choose to spend your Sacrifice Token (you must have one). Spending it consumes your move as usual (you still make whatever single ply you choose that turn). ====
* When you spend it, you grant your opponent a Double Move for their next turn.
* Immediately upon granting the Double Move you also incur a Skip Penalty: your next scheduled turn is skipped (you do not make a ply on that next turn). The skip happens only once and only to the player who granted the Double Move.
* After the skip, normal alternating play resumes (unless further tokens are spent).

==== - Granting a Double Move makes the opponent get +1 ply on their next turn (they play 2 plys instead of 1). Skipping your next turn causes you to lose 1 ply. Net effect: both players’ total plies across the game remain equal. This keeps long-run move-equality — there is no permanent move-count advantage. ====

==== - Example timeline: 1. White spends a Sacrifice Token on White’s turn (makes a normal single move). 2. Black’s next turn: Black plays two moves consecutively (Double Move). 3. When Black finishes that double move, Black’s move count has increased by 1 relative to a normal cycle. 4. White’s next scheduled turn is skipped — White makes no move during that turn (the skip cancels White’s next opportunity). 5. After the skip, turns alternate normally. ====

==== - You may not spend a Sacrifice Token if your king is currently in check (you must first resolve check). ====
* You may not spend a Sacrifice Token as a “response” to being checkmated — normal legality applies: you may only spend on your own turn and only if you have a token.
* You cannot spend a Sacrifice Token during a turn that is already the result of a previously-granted Double Move (i.e., you can’t chain-spend within the two-move sequence you were just given). But you may spend tokens on a later (single) turn if available.

==== - If a player holds more than one Sacrifice Token (variant or multiple granted by house rules), they may spend additional tokens on different turns. If both players each have pending effects (e.g., A granted B a Double Move and B granted A a Double Move earlier), apply them in chronological order. When multiple pending Double Moves would occur, they resolve on the appropriate next turns and skip penalties apply to the granters as usual. ====
* If a player would be skipped but also has a pending Double Move to take on that same scheduled turn (rare if you allowed unusual timing), the Double Move takes precedence: a scheduled Double Move cannot be executed if the player is skipped; the skip cancels that player’s turn entirely (including any pending Double Move), so tokens should not be permitted to create contradictory timing — we recommend the following safe rule: a player may not grant a Double Move that would fall on the same turn that player is scheduled to be skipped. (This prevents paradoxes.)

==== - 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).

==== - Castling: allowed as usual. If a castling move is part of a Double Move, it must be legal at the time executed (king/rook not moved, squares un-attacked, etc.). If you castled as the first of a Double Move, the second ply follows from the new position. ====
* En passant: if a Double Move includes a two-square pawn advance, and that allows for en passant capture, the opponent may capture en passant on their next opportunity per normal rules. (Because timing shifts, be careful to mark en passant eligibility and the ply count.)
* Promotion: allowed as usual.

==== - Each player’s clock runs only on that player’s turn in the normal way. ====
* If you grant a Double Move, you do not get bonus clock time automatically — the skip still consumes no clock for the skipped turn but you cannot move.
* For blitz/bullet: strongly recommend forbidding token usage or reducing per-game tokens to 0/1 to avoid chaotic time fiddling.