But it's one of those things with partners, wanting to take on that investment and risk. I think until L4D is proven, you'll probably just see what we make in that franchise.
How much has the Source engine been updated for L4D since Half-Life 2?
Lombardi: I would say that almost half the code has been developed since Half-Life 2 was released. We introduced new lighting effects, we did a lot of character animation work for HL2: Episode 2, added support for multi-core PCs, we worked on the physics for Portal and new AI added for L4D.
We look at Source as a set of tools, not necessarily as an engine that we've built that we'll use until it expires and throw away. We see it as this organic thing that we're constantly tweaking and building. It's more of a toolkit than a set engine.
It's great, particularly for older PCs, but some say its starting to show its age. Do you have an intended life span for it - a time when you think you'll need a complete refresh?
Lombardi: It's really a conscious decision, on our behalf, to make sure that our games work across a wide range of systems. And I think that we're investing more in the gameplay, AI and design than were are in textures and rendering.
If we wanted to we could beef up Source so that it'd not run on an older PC anymore, but that really wouldn't be a good decision.
That may work within the industry, and it may impress some people at trade shows, but I think when you get that out to Joe-Average, who has a two-year old PC and doesn't have £2000 to buy the latest hardware to run a game, it's not so good. We don't want that disconnection.
Portal was named Game of the Year by over 30 publications. It wasn't the prettiest game that came out last year, but a lot of people thought it was the best. And we feel far more gratified by that than winning the Prettiest Game of the Year award.
On the topic of Portal, what's going on with the sequel? We're hungry for more.
Lombardi: You're not the only ones, luckily. We thought we were on to something cool, but we just didn't know for sure because it was radical. It could have been one of those things that 20,000 people thought was really cool and everybody else just scratched their heads and thought 'What the hell is this, I don't get it'.
So we consciously made it really tight and didn't spend five years developing it with 100 people - we just built a really cool test bed, just to see if people would dig it as much as we did.
It came out on the second week of October, and the day after Halloween we got hundreds of emails from people dressed as the Companion Cube at their Halloween party.
Now we've got this challenge of living up to what we did with that. People gave it a lot of kudos for being so innovative so, in Valve's tradition, when we hit something, we're not just going to pump out more and cash in on the success of the first one.
We see it as a challenge to really innovate. If Portal was so innovative that it won all these GotY awards, then Portal 2 has to be even more so.
If you look at Half-Life and Half-Life 2 - we could have quickly put out Half-Life 2 in 18 months. It would have been on the same engine and been a reverse run through Black Mesa - we've all played those types of sequel. But that's not our style. Instead we went insane and spent six years and upwards of 40 million dollars to make the sequel.
As insane as that seems, it paid off in the end. So I don't think it'll be six years until you see the next Portal, but it will definitely not just be seeing Portal with different coloured textures.
We want to see it in 2009...
Lombardi: Perhaps. Right now, we're doing a lot of R&D to find out what's going to live up to that promise. When you think Portal you think about really innovative gameplay, clever writing and really dark humour. So how do we take that and follow up upon that idea, rather than just cashing in on it?