You are in a nano ship and must protect the heart from viruses and giant viral bosses as you protect yourself from white blood cells which have mistaken you for a virus. You will travel through veins and arteries as you battle against your enemies. You can also bring a friend along to help you with 2 player coop mode.
The aim of the game is each player is given a set of creatures, with the goal of reproducing as fast as you can, and preventing the others from doing the same. Predators will spawn and can be lured by the other players to kill the opposing teams to accomplish that goal. The last player standing is the winner.