A little camera trickery. Cute but not much else. Look not at what moves but what doesn’t. The signs in the empty stairwell at the right are worth watching.
It’s nothing more than a spliced recording, a sight gag.
Yup the Escherian stairwell is an illusion that works in 2 dimensions but is impossible in 3.
I don’t think so, because the people walking up the stairs experience the illusion. It’s not just in the video that we saw. I don’t understand the explanation that is given in the video, and I can’t find anything clear online that explains what the illusion is.