As the November release of Left 4 Dead 2 approaches, developer Valve has been continually revealing new gameplay elements, and the initial internet outcry about the co-operative zombie action game's close proximity to its predecessor has largely receded.
This week, the company detailed the new Jockey boss infected character, which leaps onto survivor characters and briefly "pilots" them around the map. Following the game's latest showing, at the Penny Arcade Expo in Seattle, Gamasutra sat down with Valve's project lead Chet Faliszek.
Faliszek touched on the game's increasing complexity, Valve's growing familiarity with its systems, and why in a procedurally-driven game like Left 4 Dead 2, a standalone sequel works better as a "single statement" than individual content packs.
"Balance is really important," Faliszek said. "Trying to do piecemeal stuff in DLC, you have a real balance issue there where you're going to have to go back and keep nerfing or expanding elements as you go on. That was one of our original thoughts when we were looking at Left 4 Dead 2, this want to have a cohesive single statement.
"The Jockey's not nearly as cool as he would be when he has the Spitter, because they work together really well" he explained, "and the Spitter's not nearly as cool without the new director AI and the Charger."
"It's all the systems working together that make it work, with all the new ammo and everything else. That's why we wanted to do it as one statement. You need to have all the pieces together to really do it big," he added.
The AI systems benefit from that in particular; Valve has learned more about "making the infected AI act like the players play" -- for example, "the Jockey will walk you into the Spitter's goo, or it'll find the Witch and walk you into the Witch."
Since it began working on the Left 4 Dead series, Valve has had to become much more familiar with that kind of interaction. "The original [game] was this interesting thing in terms of how it was so procedural -- it was strategy on the fly, because you never knew what was going to happen," Faliszek said, and that attitude was different to what the Valve team was accustomed to.
"When we first starting doing Left 4 Dead at Valve, we were just saying, 'Oh, well we normally do it this way,' but we realized people play these maps hundreds of times or thousands of times, and the experience needs to be different every time."
For Left 4 Dead 2, Valve has added scripting capability for the AI director -- functionality that will be available to modders, a community Valve still values highly.
"Talking with them and with our own level designers, it's what they wanted to have for that experience happen. It all ties in together with the AI", Faliszek concluded.