Double Move Chess

01

Objective and ordinary play

The objective is still to checkmate the opponent’s king. The board, pieces, turn order, promotion, castling, and en passant otherwise follow standard chess rules.

You may not capture the king. A game ends through checkmate or another normal terminal result, not by removing a king from the board.

02

The Double Move ability

White and Black each begin with one Double Move. It is optional and can be activated only before making the first half of a turn.

1. Activate Double Move.
2. Make one legal move. The ability is now spent, but the turn does not pass.
3. Make a second legal move with the same color. The turn then passes normally.

The two moves may use the same piece or two different pieces. You cannot activate the ability between the two halves, stop after the first half, or use it again later in the same game line.

03

Every half-move must be legal

Every half of a Double Move must be legal at the position where it is played. In particular, neither half may leave your own king in check. The position after the first half is a real intermediate position; the board is not allowed to pass through an illegal state.

The first half may check the opponent’s king. The opponent does not reply between the two halves, and the game is not declared over in the middle of the Double Move. You must still make a legal second move. That second move may continue the check, change it, or remove it, but it may not capture the opponent’s king.

Checkmate and stalemate are evaluated after the complete turn. The goal remains checkmate.

04

Captures and special moves

Captures

Either half may capture an ordinary opposing piece if the resulting move is legal. A piece captured in the first half is gone before the second half.

Promotion

A pawn may promote on either half. If it promotes on the first half, the promoted piece exists immediately and may be used for the second half if it has a legal move.

Castling

Castling may be one half of the pair if all normal castling requirements are satisfied at that moment. Rights lost on the first half remain lost on the second.

En passant

An en passant capture already available at the start of the turn may be used as the first half. An en passant target created by the first half does not remain available for the same player’s second half.

05

End of game and draws

After a completed turn, normal checkmate, stalemate, insufficient-material, fifty-move, and repetition rules apply. An intermediate position between the two halves does not itself end the game and is not counted as a completed-turn repetition.

06

Clocks and takebacks on this site

With a clock, the moving player’s time continues to run between the two halves. The increment is added once, after the entire turn is complete. Unlimited games have no running clock.

A takeback is a site feature rather than a rule of the variant. It restores the previous human decision point and is recorded in the saved game, including the number of takebacks used.

07

Double Move FEN

The Analysis board and Advanced game setup accept normal FEN plus an optional seventh field describing which abilities remain:

An m suffix marks that the side to move is between the two halves, for example -Bm. In such a position that side’s ability must already be spent.