Although simple, I quite like the idea. I found myself kind of frustrated with the fact that I couldn't distinguish the two hands as quickly as the feet. I also found it annoying that I couldn't place my hands and feet as accurate as I would like. 

I think this game would be way more fun if the snapping distance was way more forgiving, as well as adding some crazy dance effects and music. I also think it would be really funny if you were to add multiple limbs over time.

Cool idea and hope this feedback is helpful : )