A child element with no opacity (or filter:blur). Question for CSS gurus/jedi?

Question

css

The bottom line is that if the parent style is set to opacity less than 1, then it also applies to nested elements. I want to bypass this dependency and leave certain divs in their normal state while others work with opacity: 0.5;
I know about this: codepen.io/impressivewebs/details/CyfED but these add-ons do not suit me - I'm looking for a pure CSS solution.
CSS gurus, if you are into a toaster, please respond. Maybe you know if there are obscure hacks or features poorly documented in the CSS specs?
Thank you.

Answer 1

There is a thought about :hover, but I don't know how to implement
UPD: Solved. I'm working now - I can write later.

Answer 2

In general, it’s better to show some kind of markup example, from which you can already build on.

Answer 3

For good, of course, you need to create 2 children in one parent. (background and content)
but if background transparency is limited by color then RGBA can be used