Ah :) On the browser part, I've spent huge chunks of time inside of the browser viewport as a frontend engineer, also as a backend engineer and finally managing infrastructure, but never much inside browser internals and painting, layouting and that sort of stuff. I wouldn't even say that frontend performance (re trashing, re-calculating layouts, etc) is my forte, mostly been focusing on being able to mold codebases into something that doesn't turn into spaghetti after a year of various developers working on it.
The prompts themselves were basically "I'd like this website to render correct: https://medium.com, here's how it looks for me in Firefox with JavaScript turned off: [Image], figure out what features are missing, add them one-by-one, add regression texts and follow REQUIREMENTS.md and AGENTS.md closely" and various iterations/variations of that, so I didn't expressively ask it to implement specific CSS/HTML features, as far as I can remember. Maybe the first 2-3 prompts I did, I'll upload all the session files in a viewable way so everyone can see for themselves what exactly went on :)