Fourth Floor

The fourth floor is accessible by going to the third floor, going up the broken stairs, and going through the door with the lock next to it. This floor is ultimately where the game ends, in 1.5.0.

Description
The fourth floor has a broken elevator shaft on the north wall, and a door on the wall next to it. Going through the door causes the player to fall through the floor and land in the basement where the game ends.

You can also jump down the elevator shaft and land back in the third floor on top of the elevator.

Trivia

 * The lock was initially on the door, making the room inaccessible.