Spiral of Circles Optical Illusion
The image appears to be a spiral, but in fact is a series of squares arranged in four concentric circles. You can untangle the illusion by checking "show the circles" and by setting "rotate squares" to about 1.2.
This was a project for Advanced Topics in Mathematics II, fall 2016, Torrey Pines High School, San Diego, CA.
Adapted from Confusing Circles at .
 "10 Optical Illusions That Will Blow Your Mind (Photos)." The Huffington Post. (May 23, 2013) www.huffingtonpost.com/2013/05/23/10-optical-illusions-that-will-blow-your-mind_n _ 3307500.html.