Defense Grid: the Awakening was a brilliant tower defense game, but for some reason they were unable to replicate that brilliance to this second installment. Defense Grid 2 is worse than it's predecessor in every way.

Got with free games with gold and played for maybe 2-3 hours. Eh.

DG2 improves on everything from the first game. The level design is just as fantastic. The towers can now get upgraded abilities and the new boost towers are really cool. You will also need to use more than just gun towers in order to get gold medals. One of the best tower defense games ever made.