Illusion from Rotating Rings
Are the rings rotating together as one entity or are they sliding with respect to one another?[more]
If the brightness of the intersections where the rings overlap makes the rings look transparent, they slide. If not, they stick and rotate as one entity.[less]
 S. Anstis and P. Cavanagh. "Illusions from Rotating Rings." The Best Illusion of the Year Contest. (Feb 5, 2016) illusionoftheyear.com/?p=2331.