The player starts at the entry wound and must first make their way into the bloodstream. From there, they must navigate through blood vessels, making their way to the heart. Before they can reach the heart, they must destroy several nerves protecting it from intrusions.

The heart is heavily defended and they must destroy it to complete the game. The player can choose from a number of paths, and they can go back and complete all of them to collect additional DNA.

DNA can be used to evolve cells into better versions.