TIL server side image maps: https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageEl...

Supported since forever.

... of course.

https://www.ibiblio.org/gio/iconbrowser/icons/icons38.html

I really love that the source-extension icons are all different, and resemble the files contents - .c indentation, .h mostly linear, .s assembly instructions, ".o" bits