> En passant captures are the first move you tend to look at if an opponent has moved their pawn two spaces.. GP is clearly saying that you're not given the in

> En passant captures are the first move you tend to look at if an opponent has moved their pawn two spaces.. GP is clearly saying that you're not given the information that a pawn has moved two spaces, the trick of the puzzle is to infer from the board's layout that such must be the case. Seems damned clever to me. From a quick google it appears that such things are known as "retrograde puzzles".