I'm just going to bump this because its awesome, and your all monsters for not commenting about how awesome it is.
Loved Defense Grid. Loved Portal. By the rules of mathematics, I must love this!
"My great-grandfather did not travel across four thousand miles of the Atlantic Ocean to see this nation overrun by immigrants. He did it because he killed a man back in Ireland. That's the rumor." -Stephen Colbert
Defense Grid is probably my favorite tower defense game. I'm sure I'll eventually get this, but I still haven't played through those extra maps they released a year and a half ago. Still, looking forward to it.
"For a long time now I have tried simply to write the best I can. Sometimes I have good luck and write better than I can." - Ernest Hemingway