I have had this “Trippy spinning optical illusion” (found at the always interesting kottke.org open in a browser window since I found it on Feb. 1, 2016.

From kottke.org:

Somehow, this woman seems to be spinning both clockwise and counter-clockwise simultaneously. This is worse than the spinning ballerina. Anyone know who did this? Randomly found it on Facebook and couldn’t trace the source back…

The most mind-blowing of this type of animation I have seen to date. Kudos to the designer!