Anatomy of a Facebook Scam

So I got yet another post to my Facebook timeline by a relative who unwittingly clicked a series of buttons and posted a link on their page.  So I said to myself, self, I build websites for a living, surely it can't be too difficult to figure out what is happening.  So I mucked about and took some screen shots.

Click to Embiggen Animated GIF

As you can see they are laying a submit button over the comment box.  Nothing too interesting.  What these particular people are doing is positioning the Facebook box inside a large div with a background image that looks like a simple math problem.  Then setting the CSS opacity of the Facebook box to 0.  So you get to click on a Facebook button that's invisible.