Tower Madness HD for the iPad is a free tower defense type game. The object is to place weapons in the path of the invading aliens to protect the sheep (sheep?). My problem with it is too difficult at the very first level. It seems to want to force you to make an in-app purchase (using real money) to buy better weapons.
Addictive games tend to be easy in the beginning to let your learn the rules and draw you in. Addictive games also provide enough interactivity to keep you interested and engaged. Tower Madness HD simply runs on automatic pilot for wave after wave after wave of invading aliens after you place the weapons on the playing field. I’m surprised it made it so high up the iTunes iPad free apps list (it is currently #4). I’m uninstalling it from my iPad. Next!