Touch-screen defense!

TapDefense is a fun (and addictive!) free game in which you try to stave off hellish hordes from reaching the "Gates of Heaven." A touch version of popular "tower defense" real-time strategy games, TapDefense has you building six types of towers (that shoot arrows, cannonballs, ice, and so on.) to stop seven different types of enemies (everything from gremlins to succubi) before they reach the end of a winding path.

You place towers and navigate upgrade menus within an easy touch interface, and the game has excellent graphics and sound effects. TapDefense offers surprisingly rich gameplay, forcing constant trade-offs between which towers to build and where, whether to research new types of towers, and even whether to spend or save your gold--as you earn interest on any gold you save after each level. This is one of the best games available for the iPhone and iTouch, and it's a must for fans of real-time strategy games.