When we want to offer customizability to the users of our applications, things can get tricky. How do we allow users to customize the look of the user interface while reusing the static CSS we’ve already designed? There is a way, but it is fraught with many dangers. Learn about the power of dynamically generating CSS from Sass files. Tackle the foes of dynamic content injection, rendering, caching, and background processing. In the end, we will look triumphantly at our ability to reuse our application styles to create customizable interfaces for our end users.