Just about everyone is using a CSS preprocessor these days. Some like them just for the variables, and others use all the crazy inline functions and whitespace significance features. They’re often treated as black boxes. My code goes in, and CSS comes out. This talk will be a deep dive into the digestive tract of your CSS preprocessor. Learn how your original code is parsed and stored, and then how that information is used to generate valid CSS. If there’s time, we’ll also talk about introducing parasites into your system for some interesting looking results!