Found in 1 comment on Hacker News
looks like open sourced version of this

https://www.amazon.com/grind-Gears-After-Coloring-adults/dp/...

from Amazon description:

From simple to more complex, 12 designs of Mandala-like creations. The purpose is to relax, de stress and help with clearing the mind by focusing on the repetition of adding colors to patterns. There is a blank page added after each design in case markers or gel pens are used to color it in

looks like hes open sourcing based on fact it did not do too well on Amazon.

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