[PBE][AS3] Article Studies April 11, 2011July 2, 2022 http://www.adobe.com/newsletters/edge/august2010/articles/article6/index.html?trackingid=HRTDN http://www.bukisa.com/articles/228717_making-a-space-invaders-clone-with-pushbutton-the-first-enemy http://www.brighthub.com/hubfolio/matthew-casperson/blog/archive/2010/01/06/pushbutton-engine-tutorials.aspx