The acid-blooded devil is in the details for Aliens: Colonial Marines

"You can see this pocket on the pants," Brian Burleson, senior producer of Aliens: Colonial Marines says as he points to a promotional image behind him. It shows one of the Colonial Marines standing over a Xenomorph while another alien leaps at him from behind. "When we released this [image], someone said to us, 'No, the pocket is on the front of the cargo pants.' And we were like, 'Seriously?'"

That's where a lot of developers might stop caring. It's a licensed product that serious fans will probably snatch up anyway, right? How important is a pocket on a pair of cargo pants? But Gearbox Software said "We're going back in and fixing that."

The stakes are pretty high with Colonial Marines, and not just because the series has had passionate fans for decades. This isn't an inconsequential "what if" side-story like the Aliens vs Predator games, nor is it a retelling of any of the films in the franchise. It's an entirely new, canonical entry in the Alien mythology – a true, official sequel to Aliens and Alien 3 -- and the developers are taking that opportunity and running with it.%Gallery-152244%

"After this game, Alien 3 is a better film," Gearbox president Randy Pitchford told Joystiq. "I think [Alien 3] is a great film, but I think that when we came off of Aliens, some of us wanted something different. Also, there were some weird things that we didn't quite make sense of. Inconsistencies with the canon that were created. And it turns out that they're not inconsistencies – there are reasons for things. And we get to be the ones that get to connect all that up and make it clear [...] The fact that we can do it in video game form is just amazing."

Colonial Marines takes place after Alien 3, but it deals more with the plot of Aliens. The story has you journeying back to the U.S.S. Sulaco and into The Derelict on LV-426. Early on in the single-player demo we were shown, you come across the bottom half of Bishop. You will be diving deep into the motivations and plans of Weyland-Yutani. If these names and terms mean nothing to you, it's tough to say how much you will actually get out of Colonial Marines. Aliens fans, Pitchford said, are the number one priority with this game.

In some sense, being canonical means staying as true to the source material as possible. Like the aforementioned case of the cargo pants, this involves an extreme attention to detail. Brian Cozzens, the game's art director, even went as far as to try to imitate the film stock James Cameron used to shoot Aliens -- Kodak 5294 and 5295 -- which, according to Cozzens, was Cameron's favorite film stock, despite being phased out around the time the movie was being filmed.

This doesn't mean Gearbox wasn't given creative freedom, though. According to Mikey Neumann, Chief Creative 'Champion' on Colonial Marines, they weren't given any sort of "bible" or list of required story beats from 20th Century Fox. "It's much more loose and horrifying than that," he told us jokingly. "You find where the boundaries are. [...] There's some stuff about the aliens' life cycle that I got to add to, like I got to stand on the shoulders of these giants and add my own little piece to that. And even stuff as small of that is so crazy, to be adding to [the franchise]." But it's not as if the game studio was always clashing with the movie studio on creative matters. "As it turned out, I think our interests were really alike," Neumann told us. "We said, 'This is what we want to say with Aliens,' and they said 'OK.' So I think we had a really good relationship."

This includes creating new species of aliens for the universe. One of the new members of the Alien family they showed us was called a Stalker, and it seems smarter than your average animal. It will use tactics in an attempt to outsmart you, running away and using cover if necessary.

The story will be taking some of the best elements from the films, from the bone-chilling horror of the original Alien to the more action-oriented Aliens. Atmosphere played a big part in the start of the demo Gearbox showed us. You and your team of marines have never encountered the Xenomorphs before, and the tension is thick as you slowly make your way through bloody hallways and poorly lit rooms. You hear mysterious sounds around you, but you aren't sure what (or where) the sources are, much less if you're prepared to deal with them. "To make the Xenos feel scary we have to actually put them in situations that are scary," Burleson told us. "You don't have all the guns in the world, because that's not scary, when you can immediately kill things. There are situations where you don't have what it takes to kill the Xenos, and that's threatening. You've got to be careful."

But it's not all about horror, either. During the demo we were reminded a bit of the F.E.A.R. series, which has plenty of scary moments but, at its core, is an action game. From what we saw, the same appears to be true of Colonial Marines. "There are situations when you do have an entire arsenal world and you can just blow [the Xenomorphs] away, and that's really fun and exciting," Burleson said. There were moments in the demo where aliens are coming at you from all sides, out of vents and holes all around you, which felt both tense and action-heavy. Pitchford also teased sections that "are almost like first-person Uncharted," which could be really interesting if done right. We're curious to see how that turns out.

The inclusion of drop-in, drop-out 4-player co-op play can also lend itself to an action game feel, if you want to experience the story that way. Burleson personally suggests playing the game both ways – alone and with friends – to get both elements out of the experience. Co-op wasn't something we were allowed to see, though it sounds like what you would probably expect it to be.

Neumann went even further than saying the game isn't just about shooting guns or jumping out of your seat in terror. "It's not just about shooting Xenos for six hours or ten hours or whatever, then being like, 'Well, I did that!' There's got to be a lot of meat to the game. So it's not just action and horror. There's a lot of character storytelling, and there's a lot of smaller moments that become bigger moments. We're playing with all of that."

We weren't able to go hands-on with the campaign, so it's hard to get a clear sense of how the single-player experience is shaping up outside of the short demo we were shown. But from what was shown, they seem on track to appeal to the people who are already invested in this series in some capacity. If someone doesn't already care about this universe, it remains to be seen if there's a reason for them to jump in with this game, which to them might look like any other first-person shooter on the market.

Pitchford disagrees. "I think it's a great entry point into the universe. Let's say you're one of those who didn't watch the Alien films but you love action-shooter games – this is a good one, and the fiction naturally lends itself to things that work well in this kind of game genre, and because this franchise inspired so many of us and we've all been ripping it off [...] Having this entry point into the source of all that inspiration is neat because you don't have to go watch a film from 1986. You can play a modern game built with today's technology and future technology that's built for modern sensibilities, but still get that grounding point and see where the source is."

If they can pull it off, Colonial Marines could tell a very interesting story that answers a lot of questions fans might have had about the Alien franchise while also being an entertaining shooter. Gearbox is aiming to deliver a complete experience that does everything you would want an Alien film to do without being constrained to 90 minutes. "We're not building this game as a cliffhanger," Pitchford said. "The experience will be gratifying and cathartic and wholly entertaining."

Aliens: Colonial Marines is expected to launch this fall.