This is level 53 of the Main tunnel.
In this level, there are large patches of platforms, and since they are all made up of normal tiles, you can land and run on them easily. yet since the gaps between the platforms are sometimes fairly large, therefore you may need to jump on the crumbling tiles in the gap, reaching the other platform. In this way, you can beat this level easily.
There is a cutscene featuring in this level. More can be seen in here.
(Sometime after you play the Bridge Building, and you press the home button)
The Student complains about she is frustrated to push the box all over the tunnel every time she falls out the tunnel. The Runner then asks her about if she knew how to teleport without moving the box as well. The Runner then tells her that if she teleports while being very calm, the box won't move. Then, if you keep on Bridge Building using the Student, you won't need to start over every time you falls out of the tunnel. It is revealed that the Student doesn't know this beforehand as before this cutscene happens, using the Runner doesn't need to push the box in every turn, yet if you use the Student, every time she teleports, the box will go back to it's original location.
It is unknown why the box won't return to their original location if they teleport calmly, as the Runner says she had no idea, yet the Student suspects that the tunnels can sense their emotions via the movement of the air particles, thus making the box move. She thinks that this hypothesis is unlikely to be true, yet possible.
Although there are no boxes in Level 53, the cutscene happens in Level 53.