The main characters wake up in a cube, with a door on every side of the cube, and each door leads to a similar cube. Some cubes contain death traps, which either kill you instantly Alderson, or slowly and painfully Rennes. Every method of detecting traps seems to fail at some point, so for a large part of the movie, people are risking a high chance of death every time they enter a room in a desperate attempt to reach food, water, or help.
Further disturbing is the fact that the puzzle doesn't have a point: in a discussion, Worth implies that the puzzle isn't part of a grander scheme, that people are being stuck in it because "you either use it, or admit its pointless". So basically, they (and frak knows how many others before and after them) are in this situation because somebody built the cube. That's it, that's the reason. "Because it's there."
You wake up in a room, surrounded by strangers who may want to kill you and hundreds of evil deathtraps. And if you don't escape fast, you'll starve to death.
The sequel, "Hypercube" is pure nightmare fuel unleaded. Think on it. The hypercube distorts time and space, hours' (years or lifetimes for some) worth of time spent is six minutes in base reality, the overly-large cube they are traveling may just be a singular room shifting and folding in on itself constantly, that room by itself is part of a massive cube's building blocks, implying there are untold trillions of cubes stacked together into another cube construct, "the first one had rules" (implying this one does not) and finally, the final scene. My GOD the final scene; opening the only door left and seeing it opens to utter and complete 'nothingness'.
"Hypercube" had a script that the actual director flushed down the toilet, which had HONF in spades. To iterate: The hypercube consists of eight levels, and you can't go into any room you have previously been in, lest you activate the trap, which means EVERY ROOM IS TRAPPED. You have to go in sequential order. Some scenes, like level five gateway where the entire place lights up and the characters see themselves in different parts of the cube, going into infinity in all directions.... the final level is some abstract space where the shadows of four-dimensional objects are going around, seeking targets to kill by integrating with them and shifting them through dimensions (a character gets caught up in a roaming hypercube, which then becomes just a cube, making the character two-dimensional. It then becomes a square (two dimensions), a point (one dimension) and then nothing) among other things...