Four stones on the third line in the corner

Four stones on the third line in the corner  

This is the Four stones on the Third line in the Corner. Clearly, Black can play first to kill. This is unconditionally alive if White plays first.

White first  

This is usually the best path for White, making a and b miai for life. Later the cutting point at c may become a problem for Black.

Small Life  

This is simpler, but gives only two points of territory and Black's outside is defect-free.

Hane-Descend  

Playing at (hane-descend) is a mistake: Black can make ko:

Hane-Descend - Ko  

Black starts the ko by taking the vital point with .