I know, the trailer is kind of 100% vague, but hopefully it's interesting or humorous on some levels...
As far as the game goes, it's a zombie invasion simulation like you might have seen some places around the internet. Basically, a city is randomly generated (the gray blocks), and the little dots are either people or zombies. When people turn yellow, they have seen something that frightens them, and they panic and run almost blindly. When people turn green (hard to see in the video), they get weapons from a special building called "The Armory." With guns, humans can fight back against zombies on their own. Zombies are white, normal people are purple.
We had to use a very high aerial view over the simulation in order for the user to see enough of a population to have interesting interactions. This is why the people are dots and it's hard to see in the video. The game allows for up to 2000 individual characters acting autonomously, so to keep a high level of frame rate, we had to really trim down special effects and flare (sadly).
There isn't an objective, exactly, except perhaps to destroy all the zombies (if you want to save humanity). As the omnicient user, you have the ability to drop bombs on the city at your will. When you do, anyone in the blast radius, zombies or humans, will die, and buildings will also be destroyed. From the movie you'll see that there are two kinds of bombs, small ones (hard to tell in the movie) and large ones.
When the zombies infect all the humans or the humans kill all the zombies, the game is over, but you can always start with a new city or even restart with the same city.
Hopefully this helps explain what's going on in an otherwise really strange video.