Guide on using CSS

On the description page of some of the community actions, there is an allusion to using css to change what the action does or how it formats things, etc. I know generally what CSS is and the syntax, but I don’t know how to use it to modify the output of actions. Can anyone point me to documentation, or better yet an easy-to-follow tutorial?

Personally, I’ve mostly used CSS in Drafts actions for HTMLPreview outputs.

Basically, you’d be constructing an HTMLPreview object, including some CSS.

For example: review flashcards | Drafts Directory

Might be worth referencing some of the other actions you’ve already come across if you need further support.