Steam Early Access: http://store.steampowered.com/app/273500
Over 9000 Zombies! is a retro style, top down, zombie shoot 'em up! Tons of AI enemies generated by Zombie Swarm Intelligence launch themselves in marauding hordes of fiendish pests for insane zombie killing action! Choose from a massive array of weapons, build a base using automated turrets and other fortifications and survive as long as you can while killing as many zombies as possible! The game also features co-operative multiplayer so you can play alongside your friends as you fight off hordes of zombies!
The game is still in Early Access, so some features are not yet completely fine-tuned.