theres a famous optical illusion that this setup imitates. if you look at the boxes above, black circles appear at the intersections right outside your main focus

with all due respect to danpost I don't like the way the 'aliens' don't move as a cohesive unit. I created my own version of this to show how I think the aliens should move. (which by the way I think is the way it works in the original). Link: https://www.greenfoot.org/scenarios/23783

interesting idea except that it's a little hard to see the words because they're sideways, and at the home screen it's playing the song twice.