CSS preprocessors are tools that accept source and produce CSS. Very often, the input is similar to the CSS language with regard to the syntax. However, the main idea of preprocessing is to add features that are missing and, at the same time, wanted by the community. Over the past few years, CSS preprocessing has become a hot topic. It comes with lots of benefits and the concept has been warmly accepted by the community. There are two main CSS preprocesors—Less (http://lesscss.org/) and Sass (http://sass-lang.com/). Sass is based on the Ruby language and it requires more effort to run it in a Node.js project. So in this book, we are going to use Less.

In the previous chapter, we talked about building systems and task runners. CSS preprocessing and a few other tasks that we will talk about in a bit should happen automatically. Gulp seems like a good option. Let's move forward and add a package.json file where we will describe all the Gulp-related modules that we need:

{
 ...