Sanctum 2

In Sanctum 2 you'll have to use elements from different gameplay genres to succeed. Build towers and walls in the construction phase before the enemies attack, and then rush into the fray to blow everything to pieces with your towers in FPS mode. You can play through the single-player campaign alone or discover the secrets of planet LOEK III with your friends in 4-player co-op mode and find out why the aliens want to destroy the cores you've sworn to protect.