You know, I created my own bot blocker a long time ago. It goes on the basis of a hidden input and a question.

The input CSS was display:none; so that normal users can't see it. If there's text inside the box, then you would know it was a bot or idiot with styles turned off. Then I had a question that was simple, "Are you a bot?" with a yes, no, and maybe. Tested it out, and never had a bot pass through. So if you're going to bot blocks, follow what I did, because it's proven to work.