Something you talked about in the presentation was that you built systems of gameplay that interacted in certain ways to allow for emergent gameplay but then, as you saw different strategies emerge, you sort of tweaked the design to take advantage of some of the scenarios you saw emerging.

It's a big question, but how does that work? Do you just let people run into the world, see what they can actually do, and then build design scenarios based on that? Or do you have an idea of the scenarios and the powers and how they're going to interact? It sounds like you were taken by surprise by some of those things. How much do you want to start deliberately designing toward the things that emerge that you see happening as you test the game?

RC: The way we do it is we work by layers, first of all. It's a very, very vague question because, at the end of the day, it's the heart of the nature of our game. It comes from some approaches at every level. It's true for the mechanics; it's true for the level design itself, and therefore the mission design; it's true for the architecture.

So, if we talk about the level design/architecture/mission design, we come up with a little story, and an objective, whatever the objective is -- reach this place or kill that guy. "Eliminate that guy" would be more accurate, because there are multiple ways to do it.

Then, we design the environment around it. We have a rough idea of the main path that we have in mind, and this main path might be based some of the powers that we have -- some of the mechanics. We know that there might be a double jump; we know that there's a blink [teleport]; we know that the player might have the tools to possess a rat and therefore go this way or that way.

That is the first draft, and then we let it organically evolve a little bit. We let the architects do their stuff, and they add some alternate paths. Of course, because nothing is scripted so much, we put the AI in there, and all the systems are simulated, so they interact with each other; they cross each other.

We let it live for awhile, and then we see naturally some stuff emerging. Even ourselves, before it goes to the players, in fact, the devs in-house will start finding some way to do things -- which are shortcuts, which are more fun. Then, if it's a problem, we fix it. If it's, in fact, something that we think has potential, then we encourage it and expand on it. Etcetera, etcetera, etcetera.

Then come the real testers, and they might find their own other stuff. Then we add some more mechanics later in the process, and not only this new mechanic offers new possibilities, but new bugs. At this point, you keep doing this; this is why it takes so long to make the game. Even though each level designer doesn't have that many areas to work on, they work on them for a long time -- for a long time -- and maintain them in every aspect.