Kim Swift made her name in the games industry with her first game. Portal became an instant classic, and launched her career. After working on the Left 4 Dead series, she left Valve and joined Airtight Games. Her first project for the Washington-based developer is downloadable title Quantum Conundrum. She's the creative director of the game, which will be published this summer by Square Enix on PC, Xbox Live Arcade, and PlayStation Network.

Of course, as a first person physics puzzler, it'll inevitably draw comparisons to Portal. "I took what I learned from Portal, and am trying to apply similar practices of things that I feel worked, for sure," Swift tells Gamasutra. "It's like, learning good lessons and then immediately throwing it out the window, because like, 'Oh no, I'm copying this other thing'? And it was just like, why?"

In this interview, she outlines precisely what she has learned: the importance of playtesting, a collaborative, democratic development environment, and how basic human psychology can be exploited by game design.

You use techniques from painting or other media in your level design.

KS: Just general artistic compositional design.

Is that something that came out of Valve, or is it something that came out of your personal experience? Because I know Valve is also very big on pointing people in the right direction or leading with art.

KS: It was a little bit of both. I had had an artistic background before I actually went to DigiPen, and so applying all of those principles made a lot of sense to me. A lot of it is just generally human psychology of how we actually are wired to look at things, and how we actually perceive things, as human beings.

So a real basic one is we are hardwired to detect movement. So if there is movement in something, our eyes just go straight to it. And so the fastest way to attract a player is movement.

And just in general, the artistic compositional basics just apply pretty much one to one, in terms of design, because it's all about manipulating the player to get them to look at something.

Players are going to want to go towards the light, as opposed to the dark. That's hardwired into us as human beings, because we don't want to get eaten by the bad thing in the dark, and so we're going to go where it's light out and we can see. And so just taking advantage of the fact that we're animals, basically (laughs) and manipulating that, kind of behind the scenes, to get players to go where you want them to. It's actually kind of a fun game to play.

It's like a meta-game for you?

KS: Kind of, yeah. Level design is like this in general. I mean, it's a meta-game for us as designers, to take a look at a space, and we as a designer have a particular mentality of how it's supposed to be solved, what we want the players to look at, what do we want, where do we want them to go.

And so in that way, it is a game for us to see if we have manipulated you the way we wanted to -- which sounds horrible (laughs) but it's so true. A good level, a player will go exactly where we want them to, and look at the exact things we want them to, and pick up the right things without them even knowing that we had set it up deliberately that way.

You use the word "solved". Your games are about finding solutions for the most part, especially the games you have the deepest involvement with, right? So you really have to do that.

KS: Yes. It's leading the player without making them feel like they're led, because you don't want to just hit them over the head with the solution -- because that's just like talking down to somebody.

But at the same time, you want to be able to steer them in the correct path, so that way, they're not just sitting there thrashing, trying to figure out where to go or what to do. And so it's a balance, for sure. You want to add as many environment hints as possible while at the same time not making it stupidly obvious.

If we talk about it analytically -- which we should be -- when we sit down to a game, we're there to be manipulated by the creators, right?

KS: It's a little bit of both. I think it's about, yeah, you're playing into the world the designer made for you, but at the same time you're also creating your own story within this world, as well, just by your actions. So once again, I think good games have a really good balance of this. That yeah, you're doing what the designer sort of told you to, but at the same time it has enough of a space where you feel like you're really, actually making your own choices, and you're making your own decisions, and impacting this world. So yeah, it's a give-and-take.

And how much of the game takes place on the screen, and how much of it takes place inside the player's brain?

KS: I would say it takes place more in the player's brain than it actually does on the screen, because people's interpretations of what actually happened are wildly different from everybody else. Like using Portal as a for instance, hearing one person's take on what the story of Portal versus somebody else's take can be extremely different -- versus what we actually had in mind. And I think that's a good thing. I think players should impress themselves onto the game world, and I think it makes it more immersive, and makes it more fun, and I know I do that.

Like in a kind of stupid way, when I play games, I'll make up little stories for just anything. It's almost the game of making up background stories for people you see on the street. You know what I mean? And so I do that for myself when I play games, just because I find it much more enriching, and I feel much more involved in the world. And like I've been playing both through Skyrim and Arkham City, and I find myself doing that all the time.

Do you feel that there's a need, or an impetus, towards putting ambiguity in games? Leaving spaces for the player to interpret?

KS: I think that's a good thing. I know I personally try to do that. I like leaving clues for a possible story, or a possible interpretation, but I want players to come up with their own impressions of the world, I think. I think it makes it much more personal.

Do you think that's just satisfying the player, in other words? Is that your main motivation?

KS: It satisfies the player, and I also just think it's interesting. I think it's the part of what makes games really unique as a medium -- that interactivity, and being able to kind of tell your own story by your actions and interpretations. Because books and movies don't do that. Books have a very clear story that it's telling you. Same with movies -- it's from one point of view, that of the director. And what's cool about games is you are the director, and I like that. I love that about this industry.