...this will be your worst nightmare. Even if you aren't claustrophobic, you might become so. This is a true depiction of hell. Endless struggle, no time for simple comforts such as rhyme or reason, and hope is continually dashed the moment it decides to find its way back into your heart. This is primal horror. It is physical and mental, simultaneously. There is no superfluous action or imagery here: it is all to give you a sense of unease, perpetual anxiety, and oppressively enclosed confusion. It may be a little difficult for some to enjoy or get anything out of, since the movie doesn't spoon-feed you explanations or concrete (sorry for the pun, I guess) context. There is next to no dialogue, the camera shots are tight and change a lot, and you are left to create the story in your own mind with what it gives you. It isn't very long, but it is long on tension and draws you in despite yourself.