Gradient Bar Illusion

Requires a Wolfram Notebook System
Interact on desktop, mobile and cloud with the free Wolfram Player or other Wolfram Language products.
The presence of the gradient background makes it seem as though the rectangle is also a gradient, but in actuality it is one color.
Contributed by: Nathan Lian (February 2016)
Open content licensed under CC BY-NC-SA
Snapshots
Details
Reference
[1] OpenProcessing. "Optical Illusion #2 (Gradient Illusion)." (Feb 8, 2016) smtp.openprocessing.com/sketch/168577.
Permanent Citation
"Gradient Bar Illusion"
http://demonstrations.wolfram.com/GradientBarIllusion/
Wolfram Demonstrations Project
Published: February 15 2016