Unfortunately the example problems are simple enough to be solved with AI. As a test I ran two of them by CoPilot, and it solved them instantly. I like the idea, but would want something more difficult as a captcha since it is easy for bots but hard for a human.

Maybe a better approach would be to have a prompt at the top with unclear specifications, or some kind of riddle instead of a function name. It would also be good not to have a bank of problems, since someone could just pattern match on them, but to generate them automatically somehow.

This is a lot more interesting than finding traffic lights though, and the website looks well designed. Thank you for sharing!