TsumegoFromGames146/Solution

Vital point  

is the vital point. Black can answer at a or b, either of which will lead to ko.

Ko - black takes first  

This ko is obvious. Black now takes first.

Mistake  

Playing like this first is a mistake, it will allow black to live with .

Snapback threat  

If descends to the edge, white jumps to , threatening the snapback at a.

Ko - black takes first  

When black defends against the snapback with , white starts a throw-in ko with , black takes first again.

White also has the option of making seki with at a, which is sente (black must defend with at ).

Since this ko is easier to resolve for white, and since this line also gives white the extra option of making seki, black should normally choose the line of play in diagram 2.