Custom Design Options: Seeking Recs for CSS Basics

Hey Captivators! After attending the certificate workshop at Adobe Learning Summit, I'm excited to continue testing out design options. I've only done light HTML/CSS editing in the past. Does anyone have recs for LinkedIn Learning courses or tutorials that you think would provide a good foundation of CSS for the purpose of writing custom design options in all-new Captivate?

Thanks in advance!
Diane