Toggling CSS Classes with JS and Element.classList

In this live-stream, will will add buttons that toggle (turn off/on) the split background and image to better illustrate this excellent illusion by Arthur Shapiro.

http://browsertherapy.com/challenges/css-toggles-with-classlist/

See Part 1: Coding the Tissue Contrast Illusion
https://youtu.be/izoeGPX5vfA