Bent four in the corner exercises / Solution 3
![[Diagram]](../../diagrams/36/52f26942997d82b193e36a4e5435f9ce.png)
White to play
ChrisSchack:
is the vital point, and kills unconditionally.
![[Diagram]](../../diagrams/27/d8351bd0575e680541e2120e5d8e70d2.png)
Black tries to extend
If B tries to get more eyespace, W simply seals him in, and W cannot be prevented from playing a, then killing with an almost-fill by a bent four at the end of the game. This would only be ko if White needed to capture before game-end, to ensure a surrounding group's safety.