> [your browser rephrasing your text into smaller words] might be slowly becoming possible but is clearly outside the bounds of what CSS would do
When it comes to CSS, nothing seems out of scope. It's gaining conditionals (if) as we speak.
In hindsight, I wish Pavel had used something other than Z3/SMTLib for his CSS formal semantics, such as a Prolog-derived CLP language. Not that Z3 is bad, but the hope was that CSS spec authors could pick up and test/maintain the ruleset with new CSS features. Rather than unapologetically continue to add crap to CSS unhingedly. Or alternatively, expose layout to JS and then provide a common JS implementation for layout computation, as the Houdini project was proposing. I mean, that's what JS is for right?