Cobb's box world is actually a spherical non-European space. If we want to construct the escher staircase that Ariadne walked through, we must bend into a circle in the height direction of that space. In this way, the heights of the highest and lowest points of the stairs are the same, so they can be connected. In this space, there are still upward and downward directions, but the meanings are different. Up and down does not mean the increase or decrease of height, but refers to drawing a circle from two different directions.
For example, from one direction, it is clockwise up and counterclockwise down. So I keep repeating it when I go up and down. There are no such stairs in life, but many things, such as clocks and watches, work like this.