stone_juggler: I think C18C19A18A19A16D18A18 is better solution than the current one because attacker starts the ko
caranthir: Thanks for spotting that. It would indeed be a better solution, but it seems that C18 should be answered with A18, not C19; so it depended on defender's wrong answer. I updated the problem.
I think C18 C19 A18 A19 A16 D18 A18 is better solution than the current one because attacker starts the ko