From its first trailer that told gamers to "Please Remain Calm" to its release this week, Halo 3: ODST underwent substantial changes. Originally conceived as an add-on for Halo 3, ODST evolved into what Microsoft today bills as a fully fleshed-out experience.

As the final vision of the game took shape, Bungie's 70-person ODST team, which included a five-person core design team, met challenges from a personnel and technical standpoint during the course of the game's development -- which lasted about one-third as long as a typical Halo game.

Gamasutra spoke with Bungie's ODST executive producer Curtis Creamer. He's one of the 165 full-time employees at the Halo studio, which is currently working on the upcoming Halo Reach, as well as another unannounced project (for reference, when Halo 3 shipped, Bungie employed around 110-120 employees).

Here, Creamer elaborated on the hardest part about making ODST, how Bungie adapted to challenges, and the new elements that ODST is bringing to the blockbuster Halo universe.

Can you talk about the hurdles you encountered in the development of ODST? What issues did the team run into, and were people ever at odds, creatively?

Curtis Creamer: Creatively, the team really was pretty cohesive. The biggest challenge behind making ODST was that we were trying to make it in a timeframe that we hadn't made a game in anytime recently. For the previous Halo games, we're talking about three-year development cycles.

In ODST, we were shooting for about a year of development time. The challenges for us were having an understanding of just how much of a game we could make in a year, and also knowing the aspirations we were going to have, and how we were going to pull those off with all of the limitations we had as a studio.

When we were making the Halo games, it was something everyone in the studio was getting on board with, but at the end of Halo 3, we had split up. There were people working on Reach, people working on another project, and people working on ODST. We didn't have the full resources available for the project like we would normally have. We didn't really understand exactly how much we could make and how far we could push the technology.

The biggest challenge for us was with the design of the game. We decided we wanted to focus the story in one location on Earth, in New Mombasa, whereas in the previous games, you were jumping from the Halo ring to Earth to a Forerunner installation to a different side of the ring -- but now it's snowing. The environments were really different.

But with ODST, since we were putting it all in this [one] city, there were a lot of technical and personnel challenges. We had to make a city that, in various parts of the game, you're going to be able to recognize as a cohesive city. You're going to see parts of it from one side at one part of the game, and other parts of it in a different part of the game.

The city itself was really big, so the idea of making a city that had a non-linear type of movement through it was something that the Halo engine had never really been designed to do. That was probably the biggest technical challenge for us -- how are we going to create this gigantic city? How are we going to make it do things the engine was never set up to do? And then, how are we going to do it with fewer people and on a shorter timeline?