Xuanxuan Qijing Problem 23: White to play and make a ko
玄玄棋经 · Problem 23 of 347 · Placement on the 1-2 point
Black's corner is one move from life, and pushing in from outside only helps it. Look for a point inside the corner, on the edge.
How to solve it
Black's corner is one move from life. White's placement at A18, the 1-2 point, is the key.
Black's best answer is B18. White plays A17, Black takes the eye on the other side with E19, and White's B19 makes a ko, which Black takes first.
If Black blocks at A17 instead, White plays B18. After Black's C18, White takes the vital point at E19 and Black cannot make two eyes.
Pushing in at B18 first fails: Black plays A18, and after White's B19 Black lives with E19.
Main line
- 1. White A18
- 2. Black B18
- 3. White A17
- 4. Black E19
- 5. White B19
Solution checked against Sensei's Library.
Play it out on the board
Place the stones yourself and see the refutation when you miss. All the Xuanxuan Qijing problems as quick lessons.