While not CSS courses directly, these resources should help you address what you're looking for.
Tailwind related playlists on Adam Wathan's YouTube: https://www.youtube.com/channel/UCy1H38XrN7hi7wHSClfXPqQ/pla...
And this publication (by same authors as Tailwind UI, that is Adam and Steve) https://refactoringui.com/book/
Enjoy!