Usability: Clever CAPTCHA (Are you human?) that doesn’t suck

I absolutely HATE it when I get to a form and have to distinguish the letters or numbers to prove that I am human and not a robot.  Most of these CAPTCHA (Are you human?) tests suck and I have to magnify the screen 500% to try to figure out the letters and numbers.  So, I get delighted when I see clever Are you human tests that don’t suck.  On www.Builtwith.com, I found such a thing.

It simply asks me to move the slider to the cat to prove that I am a real human.  You gotta love it!