[afarrell]

If you find yourself wanting to get a solid mental model of CSS, I highly recommend blocking out a few evenings to work through The Pedantic Guide to CSS [1] as if you are a university student studying the complexities of cellular metabolism. A Spaced Repetition app like Anki [2] is really helpful here. EDIT: I've found that for best effect, write flashcards that lead you to think through some reasoning about how a layout attribute works.

You might also find the games Flexbox Froggy[3] and Grid Garden[4] useful.

[1] http://book.mixu.net/css/

[2] https://apps.ankiweb.net/

[3] http://flexboxfroggy.com/

[4] http://cssgridgarden.com/