Shortest-proof-game challenge

Shortest proof game where White can either play en-passant mate in one or make a move that allows Black to play en-passant mate in one.

I really like this idea. Here's my first attempt:

Second, faster attempt (12.5/13 moves):

And just for fun, a symmetrical one:

Faster. There might be a better way to do it though.

@5833

To be honest, I wasn't even trying to get the fastest way, I was trying to get a way.

But you had a proof game before you posted the position. That's a good thing. I wish everyone here would do the same.

I do 11.5/12.0.

Like the Ke1# challenge this one is not optimal for a white start. Half a move can be gained when black makes the first e.p. capture in RewanDemontay's version.

Not really weird. Whoever said that just wants the game to end in a full move, not so crazy

Retro-problems don't care much about full moves. As many SPG's end with a white as with a black move. The formulation of the challenge becomes a bit more abstract though: "Find the shortest proof game where checkmate is delivered by a king making a capture on it's home square". Really highbrow!

Btw, Ke1# always ends up as a half move as all white moves do! You are used to challenges where only the white moves are counted - like #13 - but proof game challenges need to be more precise!

That's pretty interesting! RewanDemontay's version with the black start is 11.0/11.5:

Proof game in 36.0 or less.

I can do it in 33.5

33.0 feels reachable, but I already spent way too long on this position

23.5

Find the fastest game where castling, playing en passant, and underpromoting to a knight are all checkmate.

That's the (non-unique) SPG.