At the risk of a thread hijack, chess fans who have Netflix should watch "The Queen's Gambit," a seven-part miniseries starring Anya Taylor-Joy as a blossoming chess prodigy. It's a 60's period-piece, based on a 1984 novel by Walter Tevis. On Fri, Nov 13, 2020 at 6:00 PM Andy Latto <andy.latto@pobox.com> wrote:
On Fri, Nov 13, 2020 at 4:54 PM Gareth McCaughan < gareth.mccaughan@pobox.com> wrote:
On 13/11/2020 20:01, Andy Latto wrote:
If we take the actual chess rules, where having no legal moves is a stalemate draw, then I think that prohibiting a move that leads to a forced
I don't think that's quite the right generalization of the rules of ordinary chess. If you compare ordinary chess with "take-the-king chess", the right way to describe what changed is that if every (otherwise) legal move leads to immediate loss then you (1) lose if a null-move also leads to immediate loss, and (2) draw if not.
So for the iterated version, the correct rule would be: if every (otherwise) legal move gives the opponent a mate in 1, then you (1) lose if a null-move also gives the opponent a checkmate, and (2) draw if not.
I agree that this is both a more consistent way to generalize, and a more interesting one.
I don't know of any positions likely to occur in actual play that would be different in this version, but it is a common theme in chess problems. It's common in mate in two problems for the solution to be a move that does not threaten mate in 1, but allows white to mate after any black move. Take for example the position in https://www.youtube.com/watch?v=GaBw9RmUoNM This is mate in 2 problem, and the solution in conventional chess is for white to play Qa8. But in twice-forshortened chess, the resulting position is a draw, rather than a win for white; white is not threatening mate but has a mate after any black move, so in the variant, black has no legal moves, so this is a stalemate.
Taking the limit as we perform this foreshortening operation infinitely often, we get the chess variant that is like normal chess, except it allows a pass as a legal move. This affects many endgames: I strongly suspect that K + B + N vs K is a draw, for example. In fact, I'm not even sure that K + R vs K is a win if the K is allowed to pass.
Unfortunately, I think the effect of any of these changes is primarily to change wins into draws, which is not what chess needs to make it more interesting.
Andy
Andy
I believe this version is neither exactly equivalent to ordinary chess, nor trivially a draw.
(By a "null-move" I mean simply doing nothing, which of course is not actually a legal move in chess.)
-- g
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