newcomers | Looking for introductions to decorative CSS on Dreamwidth? (Reply)

I really like looking at the "codes" made for playlists and roleplay blogs like the ones on criscodes. But I don't have a good baseline for how CSS and HTML can be effectively used inside of posts on Dreamwidth. Cohost, obviously, was infamously permissive with what you could do with CSS; most "modern style" social media, meanwhile, doesn't even really let you insert tables or div elements to format, limiting in-post html/css to just some very bare bones text formatting at most.

Are there any tutorials or guides for how to learn to develop your own aesthetic playlist/muselist/ac tracker/muse inbox/etc "codes" from scratch? I'd really love to brush up on my fanciest css without necessarily editing my blog theme every time to do it.