Took me a minute to realize this is developed for use with Firefox Developer Edition. If you're using Chrome or vanilla Firefox, you're going to be a bit lost when trying to follow the tutorial.
Regardless, it's a neat little distraction to do while eating lunch.
edit: clarification
firefox 42 is released to stable today.
nevertheless, I do see some of the new animation controls on firefox 42.
Plus obviously you're not a real hacker unless your software is light-on-black.