Microthemer is a visual CSS editor plugin for WordPress.

From https://sass-lang.com/guide:

Sass lets you use features that don’t exist in CSS yet like variables, nesting, mixins, inheritance and other nifty goodies that make writing CSS fun again.

One of the many features it has is allowing us to hand-code Sass in SCSS format and convert it to CSS and load on the frontend.

In this screencast, I show how Sass can be written and parsed using Microthemer: