I started with the free version of the game. After a couple of rounds, I was hooked. I was addicted to seeing and hearing the robots exploding. The game has decent graphics and sounds. The game play is simple enough. Sometimes it is difficult to select the tower you want, but with practice you get used to it. I like the achievements, but some of them are a little repetitive. Also, the upgrades interface is pretty nice. The increasing difficulties of the levels was sufficient to drive me to get more upgrades. Overall I played the game exclusively and a lot for 3 or 4 months (I still play every now and then.) My wife claimed I was addicted and I was. I would recommend this game for someone with a few minutes to kill or for killing robots. I would like to see some more maps or maybe some towers or robots based on maps. I do really love the little robots dying at the hands of my automated death towers!