[bogidon]

I only started feeling a sense of actually understanding CSS (as opposed to working on it based on acquired intuition) when I started reading the official specs. I think that most other material is an abstraction over those that usually doesn’t explain the broader context surrounding a feature or its edge cases / interactions with other features. For example here’s the spec on positioning: https://www.w3.org/TR/css-position-3/

I’ve found directly useful information in specs that was not commonly pointed out in tutorials/stack overflow/etc when discussing those features (not remembering a specific example right now unfortunately). Can say the same for JavaScript.

I think in general when learning about an API it’s best for understanding to read primary sources. And thankfully the W3C specs are quite good documents and not too inaccessible in my opinion.