kovarex:
I added alternative variation which i believe is also KO+ (more in the diff)

d4rkm4tter:
I tried the new feature here. I marked the branches as either ko+, ko- or dead. For now we have no way to do this automatically, but this opens possibilities to make really high quality collections with insight and learning value. Kovarex was looking at carpenter's square for this. I'd probably like to apply the 8 live 6 die corner rule. Let me know if anyone else wants to study a topic with this.

posetcay:
Marked disadvantageous ko branches as wrong, only advantageous ko is accepted as correct answer now.

dsm:
Why is b2-a2-b3 branch marked as mistake? It ends in a ko just like the correct answer?