Sanctum 2

In Sanctum 2, you will have to utilize elements of multiple gameplay genres to succeed. Build towers and walls during the building phase before the enemies attack, then jump into the fray and help your towers blast everything to pieces in FPS-mode. You can progress through the single player campaign yourself, or play up to 4-player co-op with your friends to discover the secrets of the planet LOEK III and why the aliens are so set on destroying the Cores you are sworn to protect.

Summary: IGDB