At the heart, the framework utilises a SASS config file to set the basic theme options such as primary and secondary colours, media query break points and few other things. We've kept this minimal by design so that it doesn't get in your way.
The easiest way to compile SASS files is to add the visual studio code plugin. This will watch for all changes and update your main css files. For further information about using SASS we recommend you check out their website.