Round corners for Openscad - Tutorial

I've been thinking on OpenScad libraries and tutorials of late, and in the process discovering more of what OpenScad can and can not do. Sometimes there are gems that I had not seen before, and I have a 'smack my forehead' aha moment.

This thing is a little bit of a tutorial on how to do rounded corners on things using the 'hull()' builtin module.

I derived from this other thing because although there is already a 'boxes.scad' that comes with the standard OpenScad, it shows that there's m