Xuanxuan Qijing Problem 18: White to play and make a ko
玄玄棋经 · Problem 18 of 347 · Reducing the corner from both sides
Black's corner is close to two eyes. Take away space from both ends of the first line and see what Black has to give up.
How to solve it
Black's corner is close to alive, but White can make it a ko. White plays A18, and Black connects at B17.
White then plays E19 on the other side. If Black blocks at D19, White's B19 makes a ko, which Black takes first.
If Black plays A19 instead, White plays D19, and after Black captures with A17 White captures at C18. It is a ko again, but this time White takes first, which is worse for Black.
Main line
- 1. White A18
- 2. Black B17
- 3. White E19
- 4. Black D19
- 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.