As you can see, (as can be seen from the animated solution below )- it turns out each dot moves independently, up and down along a straight line. I presume the toughest part (for the unknown author) was to get them all synched-up, forming a perfect circle as they move. It’s a really nice optical illusion, one that greatly reminds me of our recent “Circling Flower“. What do you think? Is it effective?