Robo Defense

Robots are trying to get from one side of the map to another, and it's your job to stop them by building and upgrading some defense towers. There is always at least one entrance, and there is always an exit directly across from each entrance. The robots will always exit directly across from where they entered. Should a robot reach the exit, you can assume that it does something terrible, because it reduces your health by 1. Source: The Publisher Website.