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Another question, this time about en-passant captures. <p> Just when is en-passant allowed? There are four cases (I'll assume for discussion that White is moving, and Black is capturing): <p> <ol> <li>White moves the Pawn in the first move of their turn, and Black captures in the first move of their turn.</li> <li>White moves the Pawn in the first move of their turn, and Black captures in the second move of their turn.</li> <li>White moves the Pawn in the second move of their turn, and Black captures in the first move of their turn.</li> <li>White moves the Pawn in the second move of their turn, and Black captures in the second move of their turn.</li> </ol> <p> Any or all of the above cases could be allowed. <a href='../multimove.dir/doublemove.html'>Double Move Chess</a> and <a href='../multimove.dir/marseill.html'>Marseillais Chess</a> allow cases 1 and 3, with the special rule that if both of White's moves allowed for en-passant capture, Black may take both of them. <p> What does Tandem-84 use? <p> Case 3 is the simplest, as their are no intervening 'moves' to confuse the issue. It would seem to me that given the board width of 7, where a Pawn making its initial move arrives in position to capture en-passant, making en-passant too easy would weaken the Pawns.