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TG53 Upper Left
PageType: OngoingGame
Moves 41-50
Dave For now let's start at W41. Where to play B40 is a separate but also very interesting question.
What is White trying to do with 41? The joseki that we see most commonly when B plays the marked stone against mokuhazushi starts with "a". In this case that would allow B to play toward the two stones inside W's moyo, most likely connecting to them and living in the middle of W's largest prospective area. Compared to this, the 10 or so points that W can seize in the corner is of no interest at all. When I play at 1 instead, I have decided to try to keep the marked stone separated from the other two and I am willing to give up the corner to do so. Playing "b" instead of 1 is a joseki move for when W values the left side strongly. However, I thought that if B simply answered with the hane at 1, it would be difficult to prevent him from making some kind of shape with the center stones. In reply to 41, B42 was probably too quick to move into the corner. B cooperates with W's idea. B should first think about resisting W's plan. The obvious choices would first of all be pushing at either 43 or "b":
After 6 here, what can W do? If 7, it looks like B can just cut at 8. The two B stones in the center are well placed to lend support and W has weaknesses everywhere. If 7 is played at 8, B will push again at 7 immediately. This still threatens to hane at the head of three stones. At the same time it threatens to play into the corner nearly forcing W to save the marked stone on the side. By now W's center is too small for W to expect to overcome the komi.
It looks like W would have little choice but to answer at 3. Now what if B pushes again? Each push expands the size of the corner if/when B decides to secure it with a play at "a". Can W play into the corner first in order to cut away B's base? It does not look like it right now. If B plays hane at "b" after W "a", what can W do next? If W hanes at 5, it looks like B can push through at 6. Not only does this threaten to break into W's moyo but it weakens W's cutting point at "b". Meanwhile, B still has the hane at "c" and the slide to "a" as defensive resources. W should be more worried than B.
I think that playing 44 is natural here as is W's answer at 45. As mentioned in the game notes, I think that 46 could be better. W47 is an all out move that expects to handle the various cutting points by fighting. The weakness at "a" in B's position is an important point when W plans to keep B confined in the corner.
Playing the hanging connection at 2 in response to 1 more or less forces W to answer at 3. If W ignored 2 in order to close the top at 6, B will immediately play the huge move at 5. W can not resist so B will expand the corner in sente, reducing W's center at the same time. This would give an easy game for B. If W connects at 5 (a connection at "a", often seen in this kind of shape in games, is over concentrated with the marked stone in this case), W can consider whether to push through at 6 or to try the knight's move at "b".
If W simply descends toward the edge with 3, W2 protects the cutting point at "a". This limits W's potential in the corner and makes it more difficult to resist something like 4.
I was really surprised by 48. I thought it was a great idea! Black would greatly prefer to break out into the center than live safely in the corner. It is not immediately obvious how (whether) W can prevent this after 48 without allowing B to build an unexpectedly large corner. Worse yet, B might now live on a respectable scale in the corner in sente. This would be a disaster for W. I played 49 hoping that B would cut at 50 which I planned to handle using the aji of "b". But I did not know how I would handle B "c" which seems like the consistent follow up to 48.
After B1, W may try 2 to keep B confined in the corner. However, when B calmly connects W has no good move next. If 4, B can safely leave the corner and play in the center to either escape with his stones there or establish a boundary that does not leave W with enough potential territory to win. If W connects at "a" instead of 4, I think that B can quietly play at "b". This secures at least 10 points in the corner and the aji of a cut at 4 remains together with the open skirt on the left.
If W tries the violent approach of 2, 4, and 6, B 7 creates a dilemma for W. B threatens to capture one W stone in a ladder with "a". If W plays around 8 (note that 8 not only stops the ladder capture with "a" but also threatens to capture some B stones with "b") to prevent this, B plays 9 and continues as shown in the next diagram...
B1 threatens to atari at 2 and capture W so W has no time to cut at "a". B3 stops the cut and threatens to play 4. After W 4, B can play in the center. W can exchange "b" for "c" but this still leaves B with 8-9 points in the corner. The marked B stones still have useful aji for center fighting or for use for making ko threats.
Moves 51-60
W51 is an attempt to close off the side in sente. If B connects at 3, I planned to play atari at "a" and then a second atari at "b". W is left with cutting points that will make the later fighting tough though. As in the previous analysis B52 should probably have been at 57 to connect underneath.
W53 could have been at 1 here. This ko is very big but the corner is only worth about 30 points. If B erases W's center in exchange for the corner, he is probably going to still be ahead - especially if he threatens W's stones in the lower center at the same time. At the same time, W has no good external ko threats. I wasn't confident that this would turn out well for me. Instead I offered B a chance to travel down the wrong path :-). B's play with 52 and 54 showed too much concern with the corner.
By the time that I played 55 I was counting on you to answer at 56. The correct play for W was still 55 at 57. Similarly the correct play for B was 56 at 57. With 56, B saves two stones that have already been closed in the corner when W played the marked stone. If B played 57 instead, W56 would be far too small. Imagine B played "a" in answer to W at 56, there is no way that W could win the ko (W has no ko threats) so B has successfully broken out on the side.
Instead, when B plays 1 W will answer with 2. When B plays 3, W can not force with 4. After 5 and 7 it looks like B can tenuki to play in the center. If later W slides in to "a", the combination of "b" and "d" are for B. Therefore W has nothing better than to block at 5 after 3. B can tenuki immediately and live in the corner if W plays 4. This is a copy of the living page "TG53 Upper Left" at Sensei's Library. (C) the Authors, published under the OpenContent License V1.0. |