Player Command Reference: Thief Commands

"Since games are closed formal systems, that might mean that games can never be art in that sense. But I don't think so. I think that means that we just need to decide what we want to say with a given game - something big, something complex, something open to interpretation, something where there is no single right answer - and then make sure that when the player interacts with it, she can come to it again and reveal whole new aspects to the challenge presented."
— Raph Koster, A Theory of Fun For Game Design (info)