Ahmad did two great reviews of the Threads app. Quite a few interesting CSS or unusual CSS technniques there.
Ahmad is an experienced designer and developer who shares highly detailed, hands-on content on his blog here.
He published two great vies, you can find them here: CSS Findings From The Threads App and CSS Findings From The Threads App: Part 2.
There are many interesting features and practices he showcases but one which I find useful is outlining all the elements rendered in a page without changing the layout, like this:
*,
*:before,
*:after {
outline: solid 0.5px #db6a7d;
border: 0;
}
This is something available as a debug tool on native platforms, quite useful for visualising render details or issues.
The other thing, which I also like a lot and advocate for, is grid for layout and flexbox for components. Most layouts can be be implemented with a single grid (more about this in a later not post) with customization abilities implmented on layout component level with flexbox (or another grid if really needed, which is rare).
Both posts are well worth your time.