Here's a few nice use cases and even examples for how to put this pseudo selector to work in your css projects. I normally prefer to use javascript for this sort of interaction, but CSS has it's uses as well.
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On :target | CSS-Tricks
The :target pseudo selector in CSS is both pretty cool and pretty limited in what it can do. In this article we discuss some things it can be helpful with, it's limitations, and some work arounds.