The Backrooms

The Backrooms is like the lobby of the game but is still used as a level.

An image of the backrooms from a 4chan post.

Description
Level 0 is a seemingly infinite non-linear space, resembling the back rooms of a retail outlet. All rooms in Level 0 appear uniform and share superficial features such as yellowed wallpaper, damp carpeting, electrical outlets, and inconsistently placed fluorescent lighting. However, no two rooms within the level are identical.

The fluorescent lighting present in Level 0 hums at a constant frequency. This buzzing is notably louder and more obtrusive than ordinary fluorescent lights, and examination of the fixtures to determine the source has been inconclusive thus far. Secondly, the substance saturating the carpet cannot be consistently identified; it is not water, nor is it safe to consume.

End
The easiest way to exit the backrooms is by wandering around until you find a bloody, floating text saying "T̸̫́ ̸̭̄E̷͕͆ ̶̤͆R̴̗̐ ̴͈̏R̶̛̭ ̴̢̊O̶̤̊ ̶̨̑R̶̠̉ ". walk under it and turn left, then take a step forward and you should fall through the floor into a test version of the TERROR lands.