Cast your mind back to Chapter 10, Building a Custom Processor, for a moment.

The key theme of that chapter was bringing together a number of plugins we covered throughout the preceding chapters, to create what would become our processor. So far, all of the plugins used were based around pure PostCSS, so they wouldn't be able to compile raw SASS code.

We took a brief look at the CSStyle library, as a possible means of getting around this—it's a great library for producing clean code using BEM principles, but it requires that code is written using a specific format. Ordinarily, there is nothing wrong with this at all—every developer's utopia should be to produce clean, efficient code, right?

Yet there is just one small problem, reality! It wouldn't be practical to rewrite a large, complex e-commerce site to use CSStyle without an enormous amount of work; it would require a lengthy transition period to effect such a change. It's not impossible, but using BEM-style...