I have a quick question - bots usually join the game, then leave within 5-20 seconds. Why not just disable chat for the first 20 seconds a player joins? That seems a lot easier, and less annoying for every time a player joins. Think about a new player loading in for the first time - the second they get in, they will be faced with an annoying question. That isn’t a very good first impression.
I’m not trying to put your work down, I think it was very cool what you did. I’m just wondering, what is the point of a captcha, in comparison to other, easier methods?