Tower defense games remain popular on phones. For the uninitiated, the basic idea of these games is that you erect gun towers that defend territory against enemy invaders coming at you along a maze or path. All the action can be contained within the space of a small screen. There’s some interaction with the app, but there’s also a “https://itunes.apple.com/us/app/apple-store/idcom.appolicious.android?mt=8″ app_id=”350906” target=”_blank”>Download the free Appolicious Android app