20x20xinfinity world

https://www.reddit.com/r/worldbuilding/comments/4ydaro/the_claustrophobic_nightmare_world/

A world where nothing can go outside of a 20x20x∞ meter rectangular horizontal tube. I came up with the idea after thinking about passenger trains and how people move through them, and I wonder what might happen if you contained an entire world within an extremely thin space. No shortcuts. There may, however, be twists and turns in the tube and hypothetically you could wormhole over. But the point is that in normal space, you can not exceed the bounds of a 20x20 meter square tube.

The laws of this world have prohibited blocking the path. Blocking the path intentionally is a felony, and if you do it unintentionally you can be fined.

Developed areas have placed a thin three person wide hallway towards the "east" side of the tube, to allow people through. These are multi-level hallways, occasionally breaking off into staircases on the outside to let people up a level. There are 4 stories of hallways, the fifth one is the outside where the sunbeam crosses through.

The Sunbeam is a track of light that alternates between glowing bright blue, dim orange, and darkness. It provides heat and light, though it varies in its brightness. Getting to close to the bright Sunbeam can result in burning yourself.

People are generally used to the very slim world that they are trapped in. Only philosophers have considered what a world with two dimensions of freedom might look like. The people have electricity: a necessity for the long distance telecommunications.

EDIT: This post is a tad misnamed. It's not meant to be an actual nightmare. Mostly because none of the inhabitants aren't claustrophobic.