Fixes

There's a couple things I did to fix this.

* You needed to add *vendor prefixes* to the css animation stuff.  The article was using codepen.io with prefix-free option turned on.
* You need to use a valid *doctype* at the head of your html.  jQuery cannot obtain the size of the window unless you have validated html.
* You need to run your script inside a *document ready* handler.  Not necessary but good to have.