TomaLexi:
+ B15 This is better according to Katago, should probably at least accept both variations.

shai:
According to Katago B4 is answered by C2 B2 A4 B3 B1 D2 A3 C1 D7 C6 A2 A1 B6 C6 B1 It's a ko but favorable for black as black has one more local ko threat at C8 and on empty board would win the ko.

shai:
O5 is marked wrong but it works after O5 Q6 S5 P7 O6 R7 R2