Bad idea: build a captcha library that embeds DOSBox so it can make you beat levels/puzzles from DOS games to continue.
Prove you're a human! Beat Lifewater Oasis from Commander Keen 4! Defeat the Yeti in Kings Quest 5! Make sure 15 lemmings survive! Get the sword in Prince of Persia!
@foone remember the goat puzzle?
@jonn which one?
@foone but yeah, "the goat puzzle" is a household name in point and click. Almost like a proper noun :)