Apparently, one of the very first proposals for a CSS enhancement was to use Cassowary-esque constraints for layout[1,2].

Think Apple's AutoLayout and similar, but in CSS. I don't recall why it went nowhere (though I do remember the reasons were more political than technical), but imagine CSS without all of the float/flexbox/grid/subgrid/etc crap, but just: `#table-a[width] == #table-b[width];` and so on. And no need for hacks involving deep `<div>` trees just to get the HTML to cooperate with CSS --- it breaks the whole "HTML is for content, CSS is for styling" premise anyway, when HTML needs to adapt structurally to CSS.

The proposal even had `@import` and `@media` (the latter named `@precondition`) all the way in 1999!

There were some attempts at revivals (e.g. [3]), but they kind of went nowhere. Personally, I'm strongly considering using it for my own (non-web-related) UI library. CSS' base syntax is okayish (the way you define classes, reference elements, etc), and the basic rules like colors or text-related things have warts, but are ultimately okay --- but anything to do with layout is an absolute mess.

[1]: https://web.archive.org/web/20140911231410/http://www.cs.was... [2]: https://web.archive.org/web/20140911231410/http://gridstyles... [3]: https://web.archive.org/web/20140907130017/http://gridstyles...