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| Opening direction of play http://www.lifein19x19.com/viewtopic.php?f=11&t=10928 |
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| Author: | PeterPeter [ Tue Oct 14, 2014 1:57 am ] |
| Post subject: | Opening direction of play |
If black should play at A rather than B here based on the principle of building a wall facing your stone near the star point, why is the answer the opposite when black has this extra stone in place? |
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| Author: | Uberdude [ Tue Oct 14, 2014 2:07 am ] |
| Post subject: | Re: Opening direction of play |
Because if white pushes like this black's extra stone is in the perfect place to safely block at 3 and then 5. So even though black blocks to the left side white cannot encroach very far into the lower side. White can make a miserable enclosed small gote life: But without the extra stone black would need to extend not hane and white gets a bigger, non-enclosed life that threatens to play at a next which isolates the lower side stones. White's push of 2 in the first diagram is in fact a very bad move, it is better to play like this: Black can now choose which direction he wants, the left side or lower side with a/b. So the point is the push of 1 doesn't mean black wants the left side, both options are still available and the exchange of 1 for 2 is good for black to make white smaller and weaker. Compare these two: Here white's corner is bigger and stronger (some other choices for 4 too (a-d or tenuki); if black doesn't play 3 then white there is a nice bulge point. |
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| Author: | EdLee [ Tue Oct 14, 2014 3:58 am ] |
| Post subject: | |
Uberdude wrote: if black doesn't play 3 then white there is a nice bulge point. Hi Peter,In other words,  is a shared local vital point:it's a good point for B ( on  ), and it's a good point for W ( tiger's mouth ).Usually, both B and W want it -- ( there are always pesky exceptions, of course  ) -- |
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| Author: | PeterPeter [ Tue Oct 14, 2014 5:28 am ] |
| Post subject: | Re: Opening direction of play |
Got it, thanks. The same idea seems to apply where black's extra stone is low instead of high. A mistake for white? |
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| Author: | Uberdude [ Tue Oct 14, 2014 6:41 am ] |
| Post subject: | Re: Opening direction of play |
PeterPeter wrote: Probably, but not always (whereas with high I would say the push is pretty much always bad: I don't recall ever seeing it played professionally). The first thing to say is black's shape here is rather inefficient with both of the marked stones low. Which one got there first? because the 2nd was probably a mistake (if knight's move in corner first then lower side extension is not important place, and if extension first then answering approach with knight's move is a bit lame). The normal sequence is again the 2nd line hane: or (10 can also be at a, because if black answers at b to keep the pressure on those 2 outside stones then white c is sente which means the corner is already alive without needing to defend at 10, also black 7 could be 8 when black is worried about the cut at d but here the lower side stones means that's not a valid fear). The idea of the push is that black has a cutting point (unlike before) which is ladder dependent. If white has the ladder he can do this: Now the solid move for black is to defend at a and white to live at b. If black plays b to kill the corner white will cut and try to kill one of the surrounding groups before his corner dies. Now in fact here the black stone on the lower side may make this hard, but even if white's corner dies if he can get a good squeeze for outside power it can be ok anyway. The reason white would want to play this push variation rather than the first diagram is: 1: he takes more of the corner from black, so black has less territory and more important eyespace here 2: he gets that wall of 3 on the left side. This push is an aggressive attacking move. However there's not much of an attack if black already has the lower side extension, but if white had strength around there the push would make sense. Btw, in this pro game from yesterday at viewtopic.php?p=174380#p174380 we see white unusually doesn't make the push down when black plays 3-3 on move 74. That's because black would counter with the c4 push herself aiming at that cutting point thanks to the f5 stone and centre thickness. (Also black already extended at c9 so can tenuki after black connects, and there the bulge point is inefficient for black. |
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