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Posted By: Timothy Chow
Date: Thursday, 12 June 2014, at 3:21 p.m.

Stick wrote:

why is Koca an 'obvious contender'?

Is "perfect" play required or just legal moves?

In chess it's just legal moves. In my opinion this is more elegant because we don't know what perfect play is except in non-contact positions.

What does 15 + 15 mean?

It's a checksum. White has 15 units on the board, as does Black. It's not technically needed for the specification of the problem but it helps guard against misprints. If you publish a periodical of chess problems with hundreds of problems per issue, sooner or later a typo is inevitable, like inadvertently omitting a pawn somewhere.

Except we can say how many moves so far? If so can we say who moved first?

There's a subgenre of chess proof games in which you don't say how many moves have happened, and you just have to find the shortest sequence. I personally find this more elegant, but the community has decided that specifying the number of moves is O.K. In the case of backgammon, I think that this sort of question should probably be decided a posteriori rather than a priori. In other words, the general principle is that the fewer side conditions the better, but if a small side condition (such as saying who moved first) improves the creative possibilities significantly, then it could be allowed.

Nack wrote:

The opening position can be re-reached in as few as five moves. Once re-reached, it can be re-re-reached in just four moves. This four move solution is a "proof sequence" that can almost be considered a "proof game."

I am not the only one to have devised this sequence, but I believe I was the first.

Did you come up with it before 1996? If not, then the famous Murat Kalinyaprak scooped you.

I'm interested in proof sequences or proof games and backgammon puzzles in general if several others here find them interesting, but to be honest I don't want to invest the time continuing to create and post what I find if only a small handful of people show enthusiasm.

If you come up with puzzles that meet the kind of aesthetic criteria I mentioned, I can circulate them among the larger puzzle-solving community for feedback. Almost anything is fair game for this crowd except knowledge of good backgammon strategy.

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