Xuanxuan Qijing Problem 14: White to play and make a ko
玄玄棋经 · Problem 14 of 347 · Placement on the first line
Black's corner looks roomy, but the stones on the edge are thin. Start from the inside.
How to solve it
Black's corner looks roomy, but White can start a ko. The first move is the placement at A18, and Black blocks at B18.
White then ataris the stone on the edge with A16. Black defends at C17, White captures with B17, and the corner is a ko.
If Black captures the placement with A19 instead of playing C17, White plays C17 and D18 and it is still a ko.
Other first moves fail. C17 is answered at B17 and B17 at A18. After D18, Black's C17 makes a twisted-four eye shape and lives.
Main line
- 1. White A18
- 2. Black B18
- 3. White A16
- 4. Black C17
- 5. White B17
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.