Xuanxuan Qijing Problem 265 / Solution

Solution  

Absurd looking !! is a necessary sacrifice to have the stone in place.

Continued at , at  

Ko at is the answer. Because allows White to connect to the corner, getting another eye.

Reference: After above  

Note that the connection to the corner is only possible with the stone. If not for it, at a kills.

Variation  

here ends in seki.

Continued  

White can't make two eyes in the center alone.