This little CSS experiment is usually the kind of irrelevant demonstration that is commonly frowned upon because it has no practical use.
But no matter how apparently futile this showcase can appear, it's still inherently valid because it maintains a clean separation between content (which in this case comprises 14 lines of HTML) and its representation (provided by its CSS styling).
Build anything and someone (usually the top comment on Hacker News) will dismiss it, mock you for wasting your time, and talk about how X was already solved years ago.
See also: the engineering dance. When two engineers meet and shit test each other on their knowledge, until both are satisfied they are better than the other guy.
But no matter how apparently futile this showcase can appear, it's still inherently valid because it maintains a clean separation between content (which in this case comprises 14 lines of HTML) and its representation (provided by its CSS styling).
I won't use it but I will learn from it.