🕸Fergus Duniho wrote on Mon, Nov 11, 2019 04:37 PM UTC:
I changed it to allow en passant only when the Pawn's double move is a player's second move, and I confirmed that this change did not break any past game. But as I was rewriting the rules, one more thing occurred to me. Suppose a Pawn's double move done on the first move puts a King in check, thereby ending the turn without a second move. If this check could not be ended with an en passant capture, this could allow a King to be checkmated in a position that would not be checkmate in Chess, and this would violate the intention behind the game.
So, I think we have to exclude the rule that en passant is allowed only when a Pawn makes a double move on the second move of the turn. This could be replaced with the rule that en passant is allowed only when the double move was the opponent's last move, or it could be replaced with the rule that en passant is allowed only when the Pawn that made a double move didn't make another move after it. For the meantime, I'll change it back to the latter.
I changed it to allow en passant only when the Pawn's double move is a player's second move, and I confirmed that this change did not break any past game. But as I was rewriting the rules, one more thing occurred to me. Suppose a Pawn's double move done on the first move puts a King in check, thereby ending the turn without a second move. If this check could not be ended with an en passant capture, this could allow a King to be checkmated in a position that would not be checkmate in Chess, and this would violate the intention behind the game.
So, I think we have to exclude the rule that en passant is allowed only when a Pawn makes a double move on the second move of the turn. This could be replaced with the rule that en passant is allowed only when the double move was the opponent's last move, or it could be replaced with the rule that en passant is allowed only when the Pawn that made a double move didn't make another move after it. For the meantime, I'll change it back to the latter.