Inspired by Mike Lawler and Son's cool snap cube investigation:
[url]http://mikesmathpage.wordpress.com/2014/11/05/studying-the-difference-of-squares-with-snap-cubes/[/url]
Some comments on making this sketch display correctly are on the Tumblr post about it: [url]http://mathhombre.tumblr.com/post/101931456149/difference-of-squares-inspired-by-mike-lawler[/url]