Rectangular Eight in the Corner
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If Black plays first, Black has several moves which grant life, from a to g. a is usually chosen because it is least affected by White's ko threats. (The enemy's key point is yours: a is also the point White to play should choose as explained below.)
is the strongest attack. is the point to avoid ko. is necessary or White plays there (or to the right of it) to capture the corner. at or will also make a seki, but White would get an extra ko threat.
Nikok34 (KGS) : Can't in this position White can make a bent four in the corner with 1-1?
Nikok34 : Now I see why ... thanks.
The Count: This isn't necessarily a mistake, is it? If White has one big ko threat and no others then White can't win the approach ko above, but can win the throw-in ko, and so Black will play and White will make seki which is better than nothing.
IronChefSakai: It seems to me that White will rarely want to play the throw-in in the previous diagram (creating the approach ko), because assuming both players know this shape well, both White and Black would have to prefer a ko over seki and White would not only have to prefer a ko over seki, but would have to be willing to settle for a disadvantaged approach ko. Can anyone verify this thinking?
Conclusion for the endgame
For the mannen-ko, the stone in the ko will be black and Black will still have the outside liberty. ( can be either or .)