Zombie Apocalypse kept making me think of 28 Days Later, but I wasn't sure why. It's nothing specific to the zombies in the game. There's no hoo-ha about a rage virus. They don't have red eyes and they don't make that cat-like spitting noise. Cillian Murphy, Brendan Gleeson, Robert Carlyle, or Jeremy Renner aren't among the survivors. It's not the setting, since Zombie Apocalypse isn't the least bit British. So why did I keep thinking of 28 Days Later?

I finally realized what it was: the music. Director Danny Boyle has a very hands-on approach to his soundtracks. For 28 Days Later, he used a piece of music called "East Hastings" by God Speed You Black Emperor. It served as the inspiration for composer John Murphy, whose soundtrack for the movie was very Godspeed. That inspiration carried over into Murphy's 28 Weeks Later soundtrack. And it's apparent in one of the musical tracks for Zombie Apocalypse, provided by longtime videogame composer Will Loconto.

You almost don't notice it when you're playing. It starts out slow and eerie. Perfect for the early stages of a level, when there are only a handful of easily dispatched zombies. It's not distracting. It's barely even present. But as it builds, so does the level of challenge. With more zombies, with more of a workload, with the odds stacking against you, with fewer places to run, you have less brain power devoted to hearing the music. By the time the soundtrack has reached its crescendo, you'll be too busy to actually hear it. The listening part of your brain has been reassigned to keep it from turning into zombie chow.

In an interview, Boyle described East Hastings as "a rhythmic looping track that builds and builds and builds. You are trapped in the headlights, it's too late, you can't get out, it's getting louder and louder...." It's the perfect musical expression of an onslaught of zombies. I'm not sure if Zombie Apocalypse is the first game to pay homage to the 28 Days Later's Godspeed-inspired soundtrack, but it's the first one I've noticed. And as John Murphy and now William Loconto have demonstrated, sometimes it pays off when musicians freely borrow from each other.