[_heimdall]

It also allows for the basic functionality without JS (and without overloading a hidden checkbox). I'm not sure how far that will get you so maybe JS will be needed for a styled and animated popover, but no-JS support with focus handled properly is nice.

I want to say there was also accessibility support built in but now I don't see it in the spec. If it handles announcing the elements to accessibility tools like a screen reader that'll really help too, its pretty easy to forget to do it manually.