Yeah, I can’t comment on that. It would have been great for the author to include a working example. All I did was cut and paste the snippets in the article to make the code run. I did have to make some slight mods to get it working though (.add method to .toggle method). I’d be interested to hear how the author might weigh in on it. I’m not sure if running this in JSBin can account for any performance issues. What’s your take? How would you make it 60fps?