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Tuesday, August 17, 2010

Shusaku Continued (Part 3)

More sweet Shusaku action here. You can jump to the beginning or use the tag Shusaku Review#1 to see all posts covering the game. White has just played a shoulder hit on the single black stone in the upper left. Now lets see how black handles the situation.

Dia. 1

First black turns at 51 to build strength and then jumps to 53 which is a standard maneuver in this situation (black could also live in the corner). After pushing at 54 and 56 white turns to expand the right side at 58. Why 58 specifically? The answer has to do with the possibilities of a second extension up the right. If white plays one point closer to black's shimari in the upper right then black can invade behind him like so:

Dia. 2

Now white does not have room to make a base on the side and the situation is troublesome. If white were to pull back a point and play at 2 then black has room for a large extension at 1. The point at white 58 is ideal for expanding the right side and restricting black's influence in the same area.

Next I want to look at white's attachment at 60. This exchange is not as good for white as simply making a two space extension to 62 because after black 63 his corner is very solid and large. If white simply makes the two space extension there is still room to reduce, probe or invade the corner. The attachment eliminates these possibilities. I suspect white wanted to reinforce the expansion at 58 in sente and then turn back to the left side and take the corner with 64 and 66. This explains why white made the somewhat crude attachment at 60. With the situation on the left settled Shusaku turns to the right side and reduces the white formation with a shoulder hit at 69. This is a strong reducing move that limits white on the right side.

94 at 78 Takes Ko

White ignores the shoulder hit to clamp at 70. This seems a little dubious to me as the thrust at 71 is very large. White salvages some territory with 72 and 73 but this gives black the suppressing move at 73 and also allows black to turn at 75 which makes white's upper right side group very thin. I think responding to the shoulder hit directly leads to a better result for white than what happens in the game.

Through 87 a ko develops but it is not terribly urgent for either side. White's stones at 70, 80-84 are light. Their ponnuki shape is difficult to attack. So white is not so concerned with the ko. Even if white had the advantage in ko threats and captured at 78 black could give way at the point below 85 and still capture two white stones and connect his stones down to 73 with the corner. This is why white tenukis to play at the big point on the upper side.

Again I think 88 to be a little dubious. It is too close to the thick black corner and invites invasion. It also does not seem to coordinate well with the white group at 70 et al. I prefer to play at 92 directly which limits the scope of an invasion. With a stone at 88, when black invades at 89 his stone has room for a two space extension so white must immediately pincer at 90. I prefer playing directly at 92 like this:

Here, if black invades, black cannot extend to get a base as easily and white can use the thickness in the upper left to attack black's stones, white 1 and 5 also reinforce the four white stones to the right. Note that black will not actually invade as in the diagram but might consider sliding underneath the stone at 1 and playing two points above it on the second line. In the actual game black was able to invade at 89. White 1 here also does more to reinforce the stones to the right than 88. Through 91 white's drifting stones in the upper right are starting to feel uncomfortable so he recaptures the ko with 94. This regains the resilient ponnuki shape and threatens to make the ko dire by playing below 85. Now black has to make a decision, if he wanted to play it safe he could connect below 85. This is very solid. But if white does start the ko black would capture first so black could ignore white's threat and continue pressuring the central stones. This is a more proactive plan but leaves some aji behind for white to work with.

That is all for this installment, I will continue to work through games, hopefully doing one a week or so. I hope you enjoy this commentary.

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