A search on Optical Illusions, (something I've always enjoyed) turns up a lot of different sites. There's tons of them at which to play around.
I found some interesting ones at Illusions.org. Especially the one below:
is trying to say the color, while the left side of your brain
is trying to say the word.
I started out "okay" because I knew what I was supposed to do. But I stumbled on the third row on the Blue colored word Yellow. And I had to concentrate on the rest and definitely felt that "left side/right side" conflict of the involuntary reflex of wanting to say the word, not the color.
And THIS ONE explains why I am not a good proofreader of my own material.
And THIS ONE is fantastic.
Put the world on "hold" for a few moments, and have some fun with optical illusions.
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Grammar error fixed: 8/16/2017