This is one fine game. I'm usually more in to games with story and developing characters but even thou this title have nothing to do with this criteria I still love it.
Drill is simple: kill all the aliens.
Gameplay mechanics is great. Weapons feel powerful and there's quite few of them as well as types of enemies. At first I felt overwhelmed by amount of the weapons and strategies to it. But as I progressed this become great strength of this "simple" game. Oh! And there's this "HORDE APPROACHING" thing... That really raises my heart beat! Great stuff.
What I love about this game is the open world-like approach to the missions. You can explore the whole map before getting into the main mission. It's great. You can use different tactics, weapons. Most areas are open so you can check geographical advantages and use them.
I will definitely recommend this title to anyone.