Beginner Exercise 148 / Solution

Black to play.  

After , White is left without two eyes.

threatens to capture the three white stones to the left of . White can not form two eyes without these stones. White must connect these stones to the rest of the White group using a or prevent Black from capturing these stones by playing , which makes a Black attempt to capture the stones by playing at a a self-atari.

Unfortunately for White, neither White a nor make life. threatens to make a second eye with , but prevents that.

The key to the problem is the first rule of killing groups: Examine a play at the eye-point.

Black failure  

Brent: For a while I had convinced myself that worked as well, but then realized that it doesn't, so I thought I'd add a failure diagram to show why. After White cannot connect at a because of shortage of liberties. However, solves White's problems. White threatens to now connect at a and live, so...

Black failure, continued  

...Black must capture there instead. But now White plays and lives: playing at b in an attempt to falsily an eye would be auto-atari for Black. So Black must connect out first, giving White the chance to play at b and solidify the second eye.

White failure  

unkx80: doesn't solve the problem, kills. After which, a and b are miai.

White lives  

However, lives.

Snapback  

at .

Bill: Now if Black plays in an attempt to take away White's eye at a, - captures Black's stones with a snapback.

Brent: Oops. Looks like I was right but for the wrong reason. (= Thanks.

White lives  

This also works. Therefore, by "problem principles" alone, one can deduce that the correct solution is at the other key point. ilan

Does not work either.  

Unfortunately, this does not work either. --unkx80