Duncan Jones‘ Source Code, which premiered at South by Southwest this evening (and ended about an hour ago), is an engagingly trippy, somewhat sentimental and yet spiritual-minded sci-fi thriller that deserves a thumbs-up for several reasons, but I was especially delighted that it hasn’t been dumbed down. It’s an exciting nail-biter, but is essentially cerebral in the manner of an above-average Twilight Zone episode from the early ’60s, and is not what anyone would call fanboy-catering or CG-driven, thank God.

(l. to r.) Source Code costars Vera Farmiga, Michelle Monahan and Jake Gyllenhaal, and screenwriter Ben Ripley (far right) on stage at Austin’s Paramount theatre following this evening’s screening.

The rumors were true: this is Groundhog Day with a bomb. Plus a little Sliding Doors, Rashomon (as screenwriter Ben Ripley acknowledged during the q & a) and a touch of Run Lola Run. Notions of reality are constantly being supposed, redefined, fiddled with and scrambled around. It keeps you on your toes but never frustrates or irritates. Jones (Moon) and Ripley work hard to involve viewers but also keep them working, and the pace and the balance are just right.

Jake Gyllenhaal plays a military chopper pilot who doesn’t know if he’s dreaming or dead or what the hell is happening…at first. All he initially knows is that his last memory involved serving in Afghanistan, but now he’s on a Chicago-bound commuter train in a sequence that loops and re-loops and re-loops in eight minute portions. And that a pretty girl (Michelle Monaghan) whom he apparently knows somewhat is sitting opposite him every time. And that some other guy is staring back at him when he glances at a bathroom mirror. And that the loop will always end with a bomb going off and scores of passengers being ripped to shreds.

Between each segment Gyllenhaal finds himself in a small padded isolation chamber of some kind and speaking to an Air Force officer (Vera Farmiga) about what he remembers and what he’s learned. The basic idea, he realizes early on, is to try and eventually figure out who the bomber is, and how to stop him. Because the train bomb is only a prelude, he’s told, and that the bomber, whoever he or she is, intends to explode a nuclear device somewhere in downtown Chicago, so he/she has to be busted in what might as well be called a repeating Source Code realm in order to be stopped in real life.

Source Code director Duncan Jones is on the far left.

What technology allows the train-bomb sequence to be played and replayed over and over? Is Gyllenhaal’s helicopter pilot dreaming, or perhaps a figment of some computer programmer’s imagination? Does Source Code-tripping provide a mere reflection of a fragment of what’s already happened and is locked in, or does it have some vague potential to reconfigure or change the future?

That’s as far as I’m going to go in explaining the basics, but it’s remarkable that so much information is packed into a mere 95 minutes or thereabouts, and yet the film doesn’t feel congested or maddeningly detailed or anything along those lines. Source Code is obviously intended to tickle and tease, but it’s not Rubik’s Cube — bright but non-genius types (like myself) won’t be driven mad.

The only mildly bothersome element is that the CG train explosions could be a little better looking (they don’t seem fully refined), and that two or three trains cars explode in flames despite the oft-demonstrated fact that there’s only one big bomb causing the destruction. And there’s a tone of alpha-emanating happiness at the end that isn’t…how to say this?…absolutely rock-solid necessary and perhaps is a little too happy-fizzy. But it’s part of a worked-out karma uplift element that ties in with death and fate and momentary eternities , and is therefore not much a problem.