Tower defense games are a dime a dozen on the Internet. Actually, they're even less than that, since most of them are free to play. Which brings up the challenge that Hidden Path Interactive has with Defense Grid: The Awakening, an upcoming tower defense game that will sell digitally for the PC & Xbox 360. How do you lure players to your product if they're already playing different versions for free? Well, up the ante in terms of features and graphics.