Think of what the word "scientist" usually means in the realm of movies. As often as not it's some cackling maniac in a lab coat, pissing in his pants and polishing his ultimate death ray. Now imagine a mad scientist movie that didn't feel like watching a movie at all--that feels like it could be happening right next door.
Our scientist character doesn't labor alone in some fortress, he works in an office park, maybe sidelines after hours in his garage. He doesn't mutter about how the establishment laughed at his brilliant theories, but he does sweat the fact that his engineering firm is likely going to put him out to pasture by age 40. He's not a megalomaniac, he's a bright guy with an ordinary level of vanity, an ordinary level of ethical blindness. He doesn't go around coldly stabbing his friends in the back to get what he wants, but he might experience a tragic failure to trust at a crucial moment. He's not out to conquer the world, he's someone who dreams of being a hero but looks in the mirror and sees an average schmuck. Then quite by accident he invents something that he could use to fix his life. And just like that he's on the road to hell.
First-timer Shane Carruth brought an engineer's merciless efficiency to writing and filming a sci-fi film for a mere $7000. His special effects amount to little more than some wonderfully believable technical dialogue. He refuses to spoon-feed you any exposition, he lets you listen in on scientists talking scientist stuff. The film starts out nearly impenetrable and only gets more so as events accelerate faster than the characters can understand them. But it's one of those films where the sense of disorientation it creates is part of the fun.