// enemy pawns in the forward direction on the neighboring files.
candidate = !(opposed | passed | backward | isolated)
&& (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0
// enemy pawns in the forward direction on the neighboring files.
candidate = !(opposed | passed | backward | isolated)
&& (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0