[limograf]

Years ago on a large project with many trainee and junior contributors, I had a sandbox.css as the last css file.

Juniors could try out new things and add in naive fixes for bugs. Then in code review we brought the change up into the cascade as a method of teaching cascade thinking.

It's rare to do that now as most front end devs are not interested in the cascade and use things like BEM instead. I can understand why - it's pragmatic - but I did personally find that a great way of building up devs who really grasped css on its own terms.