This is a typical mistake made by both pros and amateurs-the player falls into a state of euphoria, and the result is that he becomes less careful about every move. Ideally every move is played with great care, especially when each player has eight hours available. Even after using up his entire eight hours, a player won't lose on time, as he is allowed one minute per move-this 'overtime' is called byoyomi. By the end of the game, O had used seven hours and nine minutes, while Ryu had used all of his time, entering byoyomi at move 107. As a matter of fact, he spent a great deal of time on that particular move. What was the problem there ?
Reference 1 :
In the actual game, at this point Shikun played to connect his stones on the right side, by playing where white 4 is. He should have played at 1. That way, after white 2, White would connect in response (compare with Reference 2). Next Black can connect his stones with 5. Even so, White won't die when he plays 6. At the same time, his stones are not yet safe either. The best thing for Black to do is temporarily halt the attack and make territory with 7. This would have put him in the lead.
Reference 2 :
However, the big problem Shikun had was overcompensation. Of course, he knows of himself that he is an aggressive player and that, especially in an important game like this he should somehow control that aggression. His usual style called for black 1. However after white 2, and the ensuing atari at black 3, White would not connect as in Reference 1-White would start a ko with 4, because he has one sure ko threat at 6. White could then spend move 8 to recapture the ko (where the marked white stone is). This is a ko Black cannot hope to win, and that is the reason Black, in the end, used his move to connect underneath at 5 (instead of the sequence starting from 1). In other words, Shikun overcontrolled his aggression in combatting his feelings of euphoria. This overcompensating would prove to be the beginning of the end.
Diagram 1 (1-32) :
This also provides the solution for last week's question of how White should respond to black 1. White 2 is the answer, but there is much more to it, as is shown in this diagram. Black 9 is the do-or-die move that Shikun put to O. That's also the move (in fact this is move 107 in the actual game) that he spent his last six minutes on and which put him in byoyomi. Since his group has been cut in two, White has no choice but to try to escape from 14 on. Then, after black 21, White has to play at 22 to run away with the other part of his split group. This gives Black the chance to completely seal White in with the sequence to 25. Black 26 and 28 are a tactical sacrifice necessary to make life. He meant to do this in sente (keep the initiative) by playing at 32, which put five black stones in atari-and around move 14 through 22, playing at 32 would have been sente (Black would have had to respond), but after that this capture slowly loses its significance. Capturing these five stones, while freeing his two stones at 2 and 6, is worth about 16 points in territory, but the actual value is much greater as they make the white group in the lower right immune to any attack. Still it is one of Shikun's great strengths that he takes huge risks-don't forget he is in byoyomi as well, so he has only one minute per move. He goes out on a limb to try to reverse his fortune. Can you imagine what he might be trying to do ?
Diagram 2 (33-50) :
Black cuts with 33, but this might have been the losing move. White captures the five marked black stones, while freeing his two marked white stones. In the sequence to 50, however, White ensures life for his upper left group and Black has nothing to show for his sacrifice on the right. In the end Black resigned. Instead of 33, how should he have played ?
Reference 3 :
If Black plays at 1, most likely White would still capture the marked black stones. Instead of cutting at 4 next (which would give the same result), black 3 is much better. If roughly the same moves are made as in the game, Black's territory would be larger by the crossed points, while the triangular points would still be contested (meaning Black could get those as well). Territorially, this would be a difference of about 13 points, while White's group in the upper left is not completely alive yet. This would almost certainly have caused an upset.
Endgame tesuji
Problem 1 : How can Black still haggle for a few points ?
Problem 2 : White's position has a weak spot. How can Black exploit it ?
Problem 3 : Black has a splendid tesuji to decrease White's territory.
Solution 1 : Black 1 is a great move. White has no choice but to withdraw to 2 to keep some territory.
Reference 4 : If White cuts, black 3 through 5 make the corner seki, as neither White nor Black can play if they want to avoid being captured. In a seki no points are captured (although captured stones are counted). Compared to solution 1, White then loses another 2 points.
Solution 2 :
Black 1 is an unexpected move that profits fully from White's weakness here. White's best defense is 2 to 4, then after black 5, capture back two black stones (1 and 5) by playing where the marked white stone is. Black can then capture back at 5.
Reference 5 :
White 2 is a blunder as he has no response to black 3.
Solution 3 :
Black 1 makes skillful use of White's liberty problems. White has no choice but to give in and let Black connect underneath. If White is not so cooperative....
Reference 6 :
White will be left standing in the cold if he tries to capture black 1 by cutting with 2 and 4. After black 7, he loses his three stones in the corner.
