RERO_RERO:
Why I see letters on the places for stones for all variation, even before I solved this?

caranthir:
caranthir: For some reason this version has lost the variations that I had previously added, where instead of direct oiotoshi, we first take the ko (if we happen to win it, it's more efficient than oiotoshi, and otherwise we just revert back to oiotoshi). For instance: B1 A2 D1 B3 C3 A4 A3. Of course accepting these variations means that the student doesn't necessarily need to see the relevant idea (oiotoshi) allowing the sequence to work anyway independent of ko - but I don't see any other option but to accept. So I added them.