The following, highly opinionated, set of rules came about as a way to author predictable style sheets across teams of developers. Each rule can be enforced with tooling. When there is just one CSS developer on a project, spending time developing or integrating tooling may seem superfluous. However, beyond a couple of active developers the tooling will earn its time investment time and again. We will deal with the tooling to police the rules in the next chapter. For now, let's consider the syntax and the rules themselves.
To achieve more maintainable style sheets we can lean upon PostCSS, a piece of CSS tooling that allows the manipulation of CSS with JavaScript. The curious can look here for more information: https://github.com/postcss/postcss
PostCSS facilitates the use of an extended CSS syntax. For the purpose of authoring, the syntax used borrows heavily from Sass (http://sass-lang.com/). This provides functionality to make our authoring style sheets...