TORONTO — Rian Johnson’s new science-fiction noir Looper, which opened the 2012 Toronto International Film Festival, features a brain-melting take on time travel.

As Joseph Gordon-Levitt’s character narrates, “Time travel hasn’t been invented yet, but in the future it will be.”

“My character in the movie, he doesn’t really know or care how it works,” the actor explains.  “It’s something that exists in the future, and he just knows it’s his job to show up at a certain time and pull the trigger. And really time travel is not the point of this movie, it’s the setup. It’s the springboard, so to speak.”

The movie, which mixes elements of film noir and westerns into its futuristic world, centers around a showdown between Gordon-Levitt and his older self, played by Bruce Willis.

So did all the genre-mixing take some getting used to?

“I wouldn’t say that I was like, ‘In this part of the movie I should act like they do in other noir movies and in this part of the movie I should act like they do in other sci-fi movies or whatever,’ ” he says. “I think it’s a pretty unique blend — a soup — that Rian’s cooked up, and it’s just about finding the right tone for the entire movie.”

Watch the trailer for Looper below