SASS, LESS or Stylus are examples of Preprocessors for the CSS language. When using one of those, the source code must be processed (i.e. built) into CSS before it can be used by browsers.
TweakStyle v0.8.0 and v0.9.0 introduces some support of Preprocessors and custom builds:
- Source files automatically pined
- Live Update on save without having to reload preview
- Build on change to compile files
This is made possible through Sourcemap support and Watch for file change
For now, TweakStyle does not embed any preprocessor compiler. To get this working, you’ll have to setup the compiler yourself. Don't forget to enable sourcemaps and use watch mode (compile on save). You should find easily how to setup those options in the documentation of the Preprocessor you use.