[In a rare interview, Valve writing lynchpins Marc Laidlaw and Eric Wolpaw talk in-depth on the narrative structure and pithy quips behind critically feted games like Half-Life 2, Portal, and Left 4 Dead 2.]

Valve has developed a particularly strong reputation for story in its games, recently, and much of that credit can be laid at the feet of its in-house writing team. Whether it's the seamless character development in Left 4 Dead, the engrossing dystopian sci-fi of Half-Life 2, the pithy quips of Team Fortress 2, or, of course, the wickedly demented GLADoS in Portal.

Marc Laidlaw has been with the company since before the release of the original Half-Life in 1998; he started his writing career with well-received cyberpunk and sci-fi novels but moved into games once he discovered the narrative possibilities.

On the other hand, Eric Wolpaw made his name in games journalism -- both for GameSpot and, perhaps even more famously, with the satirical review site Old Man Murray; he worked at Double Fine Productions on Psychonauts before finding a home at Valve.

Here, following a well-received GDC Austin lecture, the two discuss writing process, inspiration, and mindset; and some of the creative happenstances that lead to the memorable and beloved stories and characters in Half-Life 2 and Portal.

It was interesting to hear you talk about the creative process and how difficult it is. You joked around about not doing anything for six months, during the incubation period. Do you find that that's typical for you, in writing for games -- just sitting on it for a while?

Erik Wolpaw: Yeah. I'm kind of an inveterate procrastinator, but sometimes that procrastination panic can inspire good stuff. There's a certain process of grinding through something, but then there's also those flashes of inspiration. I honestly don't know what the process is. Some connection just gets made in your brain, and you hope it keeps happening and doesn't stop.

Then, another part of the process filtering through that is that you look at something or read something, and some connection gets made. You think, "Ooh, I can apply this to whatever I'm working on."

Part of that is setting up this filter in your brain that's like, "I'm working on this thing now." So, everything I read, everything I look at, and everything everybody says to me is put through this filter of the project I'm working on. "Is this useful?" Everything you're telling me right now is first going through a filter of, "Is there something in there that I can use on the project that I'm working on?" and then it passes through and I answer you.

Marc Laidlaw: I don't know if this is true for all [creators], but it's a writing thing. If I were working on a story, and I just have a bunch of pieces floating around in my head, everything that I'm experiencing, like walking down the street, or reading, is filtered through that. Usually, that's where the missing pieces come from.

So the difference in applying that -- putting in a writer and working on a game -- is that you've got a writer who is applying that filter to the game. I don't know if anyone else working on the game necessarily thinks in terms of that, although you do have people coming in and saying, "I saw this movie last night! We should do this scene in our game!"

EW: It's not so constant. When you're really in that mode, it takes a lot of energy to keep that filter up. It's there, and you don't really notice it, but you notice it when you're not thinking about it anymore. When I'm done thinking about this thing, it's a relief, and I can start thinking about the next thing.

And you guys are obviously part of a team as well, so that filter you're talking about will also be processing stuff that other people are talking about.

EW: Absolutely. When they're talking in a room, you'll just hear a snippet of conversation and be like, "Oh my God! Can we do this? This totally fits."

Can you think of any specific instances where a snippet snowballed?

EW: One instance where the connection was made was with Portal, where we had the boss battle designed. It involved you burning up those spheres. At some point, we were sitting around talking about it, and somebody said, "Well, we never trained anyone that you can burn things in these incinerators. We're just springing this on you right there."

Note: Pictured cube unsuitable for companionship. 

There was a connection that was made right there, because we had this part in the game where you had the level with the Companion Cube. At that point, at the end of that level, you just left the Companion Cube. You just abandoned it because it couldn't go any further.

There was this connection made, like, "Holy mackerel, this can be way stronger if they force you to kill the Companion Cube, and we're also going to train you that incinerators burn things in this world." That was this moment of insight that just came from design arguments that were happening, and all of a sudden we hit on this perfect thing.