Sub-page of SpightRules



This is a position similar to a ten thousand year ko. White takes the ko, but after Black passes White should not fill.


B2 passes and W3 fills. B4 almost fills with the bulky five shape. White is not obliged to capture however, so W5 passes and B6 captures.


The gun six is not ideal and White can at least make seki.


So what if after B2 passes, W3 also passes? B4 can now retake the ko. After W5 passes, B6 should not fill either.


White almost fills with the bulky five. B8 passes and W9 eventually captures. This time, the eye shape is sufficient to life unconditionally.

Therefore, neither side should fill the ko because they end up worse off than just leaving it open. They would both like to capture the single stone in the ko, however, and this could create endless repetition. Spight rules end the game after White takes the ko for the second time, because Black passes for a second time in the same position. The game stops "unnaturally" favouring Black.

Bill: Very interesting position. :) BTW, at the end I think you mean, favouring White. If indeed, neither player wants to fill the ko -- and I think that is so --, then this challenges all rule sets except forms of no pass go. For instance, under no pass go with prisoner return Black has no prisoner, and so may as well resign after White takes the ko.


Now, if White fills the ko and Black plays at 4, I think White's best bet is to take with W5.

One eye  

W4 = pass

B1 takes the key point and play continues.

Big sacrifice  

W2 forces Black to capture.


Finally, we have this seki, which is an even score by area scoring.

Wilton Kee:

To conclude, it is undesirable for either side to fill the ko under area scoring. If Black fills the ko, Black would lose 6 points (from B+2 to W+4). If White fills the ko, White would lose 2 points (from W+2 to draw). It can be critical, e.g. if komi is -1 point. Under Kee Rules, White would win if neither Black or White is willing to fill the ko. It is justified because White captures first (see 2x1 board in Kee Rules).

SpightRules/Example last edited by WiltonKee on June 10, 2013 - 16:10
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