cssmin is unmaintained & has a bug with complex :is selectors
Sometimes I want to have a just a tiny bit of CSS that’s unique, just for one page or post. I don’t want a whole stylesheet, or to have to add this to my site-wide theme, just for one post – I want a simple way to add it in the post itself.
This is how I did it:
You can use the new CSS :is selector to write complex CSS selectors in a much more compact way