Sounds like they're doing a lot of work to help you play with pals. Only this time it's a terrible giant spaceship filled with terrible space monsters, and you've got weapons like space guns and stasis grenades. Looks like it's very much doing that sort of thing, y'know. Which is a description of The Anacrusis that applies to Left 4 Dead just as much. An AI drector is overseeing the action, spawning enemies, bosses, and items to challenge you. So there you are, in a terrible place with your pals, pitted against a horde of monsters. Monster hordes look a bit ropey but hey, I'm feeling hopeful.