This trailer offers the E3 2011 playthrough demo for XCOM, with more than 20 minutes of gameplay and cinematic footage from the upcoming FPS installment in the classic UFO strategy series (thanks GayGamer). This includes an introduction from narrative director Jordan Thomas explaining the "pretty aggressive design changes" they've made to the game over the past year because it just wasn't "XCOM" enough for the hardcore fans of the original games at 2K Marin, who serve as our creative conscience." Here's that intro:

Hey folks,

So we've been flying under the radar with XCOM, for about a year -- and felt that it was about time to put together a little video update in order to lift the curtain on the reasons why.

2K Marin had just finished working on BioShock 2, and that game will always be deep in our DNA -- but our first crack at adapting XCOM to a more personal, real-time experience was way too much within our creative 'comfort zone'. It was kind of a run-and-gun affair, without a lot of focus on the command of your squad, or indeed on tactical play itself.

Candidly, it just wasn't "XCOM" enough for the hardcore fans of the original games at 2K Marin, who serve as our creative conscience. So over the past year, we've made some pretty aggressive design changes, in pursuit of the feelings that we experienced when we played the original games. I'll cover those in the video itself, but a quick note about story:

Narratively, XCOM is an all-new origin story in its own timeline; a deliberate reimagining along the lines of something like Battlestar: Galactica or Batman Begins. What that means in practical terms is that while we take narrative inspiration from the original games, we have also deviated in a couple of key ways. For example, our game is set in 1962 within the continental United States -- at the moment the XCOM organization is formed.

We wanted to tell the story of the first man on the ground -- exaggerating cold-war fears about invasion from within -- via this alien threat for which there is no precedent. And we felt the best way to express that kind of intimate take on the XCOM universe is from that character's perspective: limited information, overwhelming odds, and direct personal involvement.

In our XCOM, you play William Carter, Special Agent in Charge of field operations at XCOM. So as you start up the video, I'd like you to slip into his shoes as he reviews a piece of evidence which was discovered somewhere out there in mid-century America.

Hope you dig it -- there's a whole lot more to come.

- Jordan Thomas