A flash version of the popular desktop tower defense game. Place defensive towers of various types to kill the aliens as they try and navigate through to the other side.

Click a structure, then click on the map to build it. Structures can be upgraded, or sold if needed. Hint: it helps if you build a maze with your towers for the aliens to have to navigate through, as this makes them take longer to reach the exit (and thus gives your towers more time to shoot them).