svg spinners
https://jnorthrup.github.io/spin/
This article is a bit more recent than the code, but this visualization is a kind of open-mindedness demonstration of your brain correcting what you perceive. you will experience your eyes involuntarily fighting the picture.
excerpt: https://nomadrs.com/open-minded-people-different-visual-perception-reality/
What is it about a creative piece of work such as a painting or music that brings us feelings of awe and wonder?
Is it the thrill of being shown something new and different? Something the artist saw that we could not?
As Pablo Picasso put it:
“Others have seen what is and asked why. I have seen what could be and asked why not.”
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They then tested who experienced a visual perceptual phenomenon called “binocular rivalry”. This happens when each eye is shown a different image from having red and green patches over each eye. The result is having different images being displayed to each eye.
Most people will switch back and forth between the two incompatible images, as the brain struggles to perceive the two images at the same time.