When i was a little kid, I was really scared of the dark. But then I came to understand, dark just means the absence of photons in the visible wavelength -- 400 to 700 nanometers. Then i thought, well, its really silly to be afraid of a lack of photons. Then i wasn't afraid of the dark anymore after that.
Elon Musk

:focus-within

The :focus-within CSS pseudo-class matches an element if the element or any of its descendants are focused. In other words, it represents an element that is itself matched by the :focus pseudo-class or has a descendant that is matched by :focus. (This includes descendants in shadow trees.)
:focus-within css reference