Beginner Exercise 20 / Solution

White to play  

plays on the vital point. is forced - else White plays at the point and leaves only one eye for Black. ! is a good sacrifice to remember.

Black captures  

After throw in, Black can't connect at for shortage of liberties. After captures, make the eye false and kills the group. Note that the marked White stone is essential - if not for it, connects at and lives.

Failure

straight four  

here is a mistake - completes a straight four, with a and b miai for life.