I remember playing the heck out of this game when it came out back in 2009. It’s a fairly traditional tower defense game but the draw is the vector graphics and unique range of weapons. It can also be pretty tough and chaotic at higher difficulties making it an addictive game. Like Geometry Wars you will see colourful bits flying all over the place giving it a very satisfying feel and something interesting to look at while you wait for your towers to defeat a wave. Definitely worth picking up as this is one of those games that rarely goes free (first time if I’m not mistaken). If you like this also pick up the sequel geoDefense Swarm ($1.99) which switches the playing field to a hex layout making it more tactical and tough.