Creation of this applet was inspired by a [url=http://www.gogeometry.com/school-college/3/p1202-four-squares-two-equal-parallelograms-online-tutor.htm]post[/url] from [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url] (GoGeometry). [br][br][b]Feel free to move any of the present (or soon to appear) BIG POINTS anywhere you'd like at any time. [/b][br][b][color=#ff00ff][br]How can we formally prove what is dynamically illustrated here?[/color][/b]