Practical Endgame Test 1 / Solution 4

Alternative  

In the solution Black plays at a. What if Black plays at 1 in this diagram instead?

--ArnoHollosi

White wins by 3  

If White plays 1 here she only wins by 3 points and not by 4 points as in the solution.

White wins by 2  

If White plays 3 here Black answers calmly at 4. White cannot block at 6 now, as she would be two points worse off than if she had played at 4 immediately (instead of 3). So Black plays 6 - the sequence unfolds up to 10, next a-d follow. This time White only wins by 2.

Good Kikashi  

DaveSigaty: White answers 1 with 2 as a kikashi (forcing move). As a result, when Black cuts with 5, White 6 is sente.

Result White wins by 5  

White 8 connects at 3. Actually Black 3 is pointless since he could never fight the ko. Therefore whoever plays 3, the score will be the same in this area. After Black protects the cut at c, the result is W+5. White has forced a better result than the solution diagram.

No eye in the corner  

The marked white stone is an interesting play for more than one reason. If the marked exchange has been made, then even if White plays elsewhere after 1, Black can not make an eye in the corner. Without the exchange, Black 1, 3, 5 will make an eye and 4 points of territory. In addition, a white block at a is gote. After the exchange, Black gets no eye and only 2 points from capturing the extra stones that White adds. In addition, the white play at a is sente. Finally, White has the option to answer 1 with a ko at b if that is what is necessary in the overall game situation. Let's see whether that would be a good idea in this problem...

The Ko Fight 1  

6, 9 take the ko. White initiates the ko with 2, counting mainly on the series of ko threats in the bottom right.

The Ko Fight 2  

5, 8 take the ko. Both sides work through their inventory of ko threats.

The Ko Fight 3  

4, 7, 10 take the ko. Black 5 looks like a desperation play but it is not. White is also out of ko threats so things get very interesting. White has no other play than 8, but 9 is a clever reply that creates a ko threat at a and protects against 8.

The Ko Fight 4  

6 takes the ko. B has time to answer calmly with 4 at 5 because White has no other ko threats. White ends the ko with 8 but Black eats into the upper left corner. Black cannot resist.

The Ko Fight 5  

3 connects the ko, under the marked white stone. The final result is W+3. White has not improved on the solution diagram by fighting the ko.