Paul Conroy (Ryan Reynolds) wakes up to find himself in a wooden box barely larger than his body, buried in the Iraq desert. In the box with him are a Zippo lighter, two green glowsticks, a flashlight that barely works, and a battered cellphone displaying Arabic text. This last object is the most important: it is the only tool Paul has to find out why he is in a wooden box buried in the desert, and to attempt to find some way to safety. There is no other set, and excluding a video watched on the phone, no other human being seen during the whole movie.

One must at a minimum concede that Buried boasts an elegant premise of inordinate simplicity.

The film is, admittedly, an exercise. Who Paul is, and why he is buried, and how if at all he is to get out, runs a distant second in the mind of director Rodrigo Cortés to the grander question: exactly how many different ways are there to film a man in a coffin, and how many of those can I get to in just 90 minutes? The answer is "a whole lot", and one of the chief pleasures of Buried lies in how remarkably fluid and variable and just plain interesting a movie can be that takes place entirely in one intensely confined location with but a single actor's face to occupy us for the whole running time.

After an immensely successful opening credits sequence that instantly calls to mind everyone's favorite modernist motion picture graphic designer, Saul Bass, the film plunges us into black. Slowly, steadily, we here the sound of man breathing: disoriented, sleepy, worried. There's a pounding - then a click. The click is his lighter, and as it flashes for a split second, we see his eye filling the frame, alarmed and gushing sweat. He finally gets it to light, and the camera pulls slowly back from that extreme close-up, down the length of his body, revealing wooden walls on every side and pitch black beyond. The shot ends at Paul's feet, gazing back at his face, which wears an unmistakable "oh, fuck" expression. You can't do much better in my book than a bravura opening, and boy oh boy, is it ever a bravura opening we get in Buried.

From there... what can one say? The film is an insanely accomplished experiment in finding new angles from which to shoot the inside of a terribly under-lit coffin. Nor is it style for the sheer sake of style: every new trick that the filmmakers trot out is very clearly and necessarily tied to the specific emotional beat of that particular moment. The "plot", if it deserves such a word, largely consists of Paul trying to get in touch with someone who can help: first he rather optimistically dials 911, to find the operator (Kali Rocha) can do nothing to help him, and obviously thinks him a crank; he can't reach his wife, Linda (Samantha Mathis); his kidnapper (José Luis García Pérez) doesn't speak enough English for Paul to get anything useful out of him besides a deadline for a $5 million ransom; Dan Brenner (Robert Paterson), in charge of finding abducted persons in Iraq, seems rather more inclined to give him the runaround than to do anything that will actually extract him from his tomb. As he goes from one dead end to another, Paul gets increasingly frantic, and increasingly incoherent, and, it must be said, increasingly stupid: but then again, there's not much air to be found in that sort of place, and his untethered behavior is very suggestive of a man starting to suffer from a lack of oxygen.

But back to my point: that at any given juncture, Paul's terror is a different flavor of panicked, which Cortés visualises in a number of different ways, aided by the extremely valuable talents of Eduard Grau, the young cinematographer whose only other prominent work has been last year's grimly over-conceived A Single Man. Grau and Cortés work some kind of magic in this film, which positions the camera in places that you'd swear a camera could not go, which lights everything using the scantest light possible, which at all turns subjects us to the same hellishly claustrophobic experience that Paul must suffer through. The film was shot with the 2.35:1 aspect ratio, but I suspect you could count on your hands the number of individual shots to exploit the full with of that frame; for the most part, the filmmakers instead fill their widescreen image with oppressive amounts of negative space, trapping Paul not just within the cramped box that defines the film's universe, but then trapping that box within a suffocating frame. No film since 2005's excellent horror film The Descent has thus exploited black space within an anamorphic widescreen frame to anything like the same effect, and The Descent only does it here and there; Buried does it in virtually every single shot, and it is hideously, wonderfully grueling.

Other praise must go to the film's sound team, led by James Muñoz: if anything, the use of sound in Buried is even more important than the visuals. That horrible, muffled, flat quality that you hear when you're in a tiny place? That sound permeates every inch of the film, and often (for it is frequently the case that all the lights go out), it is the only narrative cue we have. It's an impeccably stifling soundscape we're faced with here, making the film every bit as claustrophobic to listen to as it is to watch. I might as well also call out composer Victor Reyes, whose score never, ever dominates the movie, but is always worked in as an organic part of the soundtrack (organic, but, of course, non-diegetic), adding to the emotional pull of a given moment almost subliminally.

All of this is tied together by Reynolds's shockingly, impossibly great performance. He's in virtually every frame, him or a foot double; the absolute only anchor we have is his face and his fear. Reynolds sells this character as well as he possibly could be sold, given that the entire performance can and must be nothing but a descent into increasing terror and anger and misery. It's a brilliant performance, painfully physical, and far beyond what I would have ever expected from this man, even as he's slowly demonstrated in the past couple of years that there's some definite talent behind his pretty boy looks.

So far, so good: and like I said, it's mostly just an exercise. Can we replicate the feeling of being buried alive cinematically? Yes, resoundingly, enthusiastically yes. A most glorious exercise, and one of the great thrillers of the last couple of years. But it all gets mucked up because of the damn script, by Chris Sparling, which actually has something to say about Iraq, and while a little bit of context is necessary (there's nothing interesting about a man with no past suffocating in a box), the parts of the film where the message movie theatrics dominate the more elemental study of a man reflecting upon his fate as his air runs out, these are by far the weakest moments. Innocent people got hugely dicked over by the establishment in the course of the Iraq War; this is true beyond a shadow of a doubt. Everyday Iraqi citizens were driven to violence and extremism in a desperate attempt to preserve their country? Of course they were, and they should have been. Deep down, most of us know that it makes no sense that we're over there? I'd like to assume that's the case, but I'm a nutty pacifist liberal. These are all worthy points for a work of art to raise. They are also distractions; they threaten to reduce the incredible impact of the film's creation of a cramped wooden hell, turning it into a pretext for a political cartoon.

It's also frustrating when the movie adds fake drama, which it does twice: once in a scene where a snake manages to get into the coffin through a knothole (which, while undeniably contrived, does work as a tension-builder), and once in the final moments, a pointlessly over-done bit of drama that ends the movie on an unnecessarily mean note - adding, in the process, to the urgency of the film's political argument.

Frankly, though, I found it absolutely easy to ignore these flaws, particularly since a great many of them were worked into the film invisibly enough that I only really realised how much Buried was a political essay after it was over. It works so well as pure cinema that anything else is just background noise, ultimately.

And yet, pure cinema though it is, I find myself tempted to recommend against seeing it in a theater (based solely on my own experience, which was kind of horrible). Buried relies for its effect so much on the precision of its lighting and its sound, and these things are difficult to control: the bright "EXIT" signs and low rumble from the next theater and the yammering couple in the back row who clearly weren't that into the film and whatever the hell was going on with the cheap-ass chain theater projection, the right edge of the frame was noticeably lighter than the rest, not that I'm complaining about anything specific, that's shoddy criticism. But still, it's so much easier to control these things in your own home... I sort of adored Buried, so there's that, but I also kind of wish I'd been watching it on Blu-Ray.