Thanks, and I can definitely relate to not wanting to assign complexity to one's own work. I think the trick there is that, once you know how to do something, it doesn't seem hard, even if acquiring the knowledge and skills to do it is itself quite a challenge. And I agree that, in some senses, it's not /that/ hard - I mean I'm not proving P=NP, here. It's a software engineering problem, with existing solutions. That said, there is a spectrum of difficulty, even within software engineering problems with existing solutions. Fizzbuzz is less complex than distributed systems. This particular problem strikes me as rather difficult, and one way you can tell (beyond the stuff I mention in the post around serialization, UI paradigms, meta applications, etc) is that earlier models /couldn't/ do it. Which is why Fable being able to, when they could not, was so exciting to me.