Shortest-proof-game challenge

38.5 so far.

I had made a 43.5 move game to make sure it was legal and wanted to see how much shorter it could get.

Interestingly EvinSungs "illegal position" in the other thread has the king on d6. Now it is on h8 - probably because this position is "legal". But that change is unnecessary since EvinSungs "illegal" version with the king on d6 in the Illegal Position topic as #7725 is also legal! See my post there.

Actually, the king is on h8 here because that's where it was before EvinSung changed the position again to move it to d6 in an unsuccessful attempt to make the position illegal.

I thought something like that but I couldn't reconstruct the history with EvinSung changing the diagrams!

This forum has been oddly silent for the past two days. Here's a fun little position I made; can you beat my solution?

Rocky's solutions to the fastest white/black mate were impressive! Here's another 4.5 solution in which the existence of the black rook and knight are really annoying me:

Does my solution at least tie with yours?

It is actually the exact same as my solution. I was hoping to create a unique solution, but I'm not sure if there are any duals. Did you find any other 10 move solutions or perhaps a way to reacher the position in a shorter amount of moves?

Jacobi found exactly two solutions, here's the other one:

Interesting, it appears both solutions have a unique sequence!

This position has four solutions of the same length that each have a unique sequence of moves (I hope). Is it possible to make a position with more?

Any particular solution has a unique sequence of moves, or it wouldn't be that solution. And there are many positions with more than four proof games of a given length.

I see what you mean. When I said unique sequence, I was intending it to mean "unique order". In other words, if a position is reached using a certain combination of moves, there is only one way for that particular combination to be played in order to reach the position in the shortest amount of moves.

I'm still not sure what you mean. What is a "certain combination of moves"? Any two consecutive moves by the same side would be a combination of moves.

I can only find two 9.5 move shortest proof games for #5895. Are you claiming there are four?

i think that if e4 xx Nf3 is in a solution for white to reach the position, then Nf3 xx e4 absolutely can not be

ie all the solutions have a different set of moves (piece moved, starting spot, ending spot, any capture, any promotion) but no permutations

For the ending position of the game posted above (#5899), can you find the twelve solutions of "Proof Game in exactly 3.0"?

@5900

4 ways to lose a move for black: ...Qe7, ...Qf6, ...Qg5, ...e6
3 ways to lose a move for white: f3, g3, g4; g3, f3, g4; g3, g4, f3
4 * 3 = 12

9.5 is the shortest proof game, and technically speaking there are four different methods to get the position in 9.5 moves (they are basically the same).

The definition of words can be confusing! I remember there being an argument about the meaning of "deliver" in a recent forum. By "combination of moves", I meant the collection of moves used to reach the target position, where order isn't considered. I think it's best to give an example of what I meant:

In hindsight, I realize that it is remarkably easy to create positions of this nature, and that I sound very stupid.

What I tried to do with #5895 was to create a position where all shortest solutions had a unique order for the specific collection of moves of that solution.