It seems to be thought of as quite a feat to stump the Headmaster.

Ahem. I don't know whether to be flattered or pissed off. A game within a game, eh? Remember, I'm the Scorpio.

I haven't been stumped yet... and you'll see what I'm going to do; it's all worked out. But now, I think I'll wait to post it till tomorrow. Just to keep you guessing.