Seeing Monkey Around in action might leave you wondering how the numbers
of red and blue monkeys change just by moving the handle. You can see
that the picture doesn’t actually change, its parts are just rearranged.
This observation is the key to understanding how this exhibit works.
This is an example of a geometric vanish – a clever way of shifting
pieces of a picture around to create the impression that something is
gained or lost, but really only the positions have changed. Pay careful
attention to how the monkeys are rearranged in the video to understand
how this is done.