The low-key Spanish import Fermat's Room falls into that (very small) sub-genre that I've just now designated as "math horror." (Vincenzo Natali's Cube also belongs in this group, and maybe even a few other movies that I can't think of right now.) This is a strange but engaging Spanish thriller in which four well-established mathematicians convene after receiving a mysterious invitation, and then find themselves trapped inside a shrinking room. The only way out is to solve a bunch of math riddles, but the biggest question is this: Why the heck is someone trying to kill four mathematicians in the first place?

Handsomely shot and boasting fine work from its five main only actors, Fermat's Room is the sort of mystery / thriller that will appeal to folks who enjoy a good mind-bender as much as they dig a good foreign flick. It's certainly not as bizarre (or nearly as bloody) as Natali's Cube, but I'm betting the films would make for a pretty interesting double feature all the same. And while some of the in-movie puzzles are relatively obvious (hell, they even borrow one from Jim Henson's Labyrinth!), the movie as a whole proves to be sort of a puzzle in its own right. The third act revelations might not be all that shocking, but they work well enough in the low-key context of the piece.

Without spoiling too much, I can tell you that one of the invited is a 22-year-old math phenom who, a few years back, was about to solve a very old and very difficult equation -- but someone trashed his apartment and ruined five years worth of research. Now he's (most likely) the only one who can save his fellow "guests" once the riddles start getting difficult. As played by Alejo Sauras, he's the character you'll root for from the outset. Also along for the numerical nightmare are an irritated inventor (Santi Millan), a pretty young genius (Elena Ballesteros), and a seasoned old math wizard (Lluis Homar). Their host, of course, is a guy called Fermat (Federico Luppi) -- although not even the party-thrower seems to know all the answers. Or even all the questions. And it's a darn good thing that each of the actors are solid, because you'll be spending about 80 minutes with them, yelling at one another in a freaky shrinking room.

I'm still not exactly sure how all four walls of a room could compress inwards at the same time, but co-directors Luis Piedrahita and Rodrigo Sopena do a fine job of mounting a basic-yet-compelling thriller that not only has a brain, but also a pulse and a strong visual style. Even if you figure out half of the flick's puzzles early on, the actors are more than strong enough to keep the 88-minute experience moving along colorfully and confidently -- even with the material gets just a little bit wacky. There's always something to be said for smarts and efficiency, however, and the co-directors do a fine job of spinning their strange little story with a minimum of muss, fuss, or extraneous blather. And let's face it: Math is scary all by itself, even without the mysterious parties, angry strangers, and a freaky shrinking room.