This is a creature based sim where your creatures will breed passing their genetics onto their children. There isn't a goal per se, but this game is more about setting up and seeing how the creatures evolve.
There are 3 different types of creatures:
Humans: Yellow Squares. They are the smartest with their movement and will shoot from a distance. They have low birthrates (2 children per mating)
Aliens: Small Purple Squares. They attack via melee. Aliens move fast and tend to rush enemies. They have high birthrates (3-4 children per mating)
Zombies: Large Green Squares. They attack via melee. Zombies move slowly and reproduce by spreading their virus to an Alien or Human. Their bite has a small chance of infection. Once infected the affected creature will steadily lose health and die. Upon death the Square comes back as a Zombie and gets a roughly 50% boost to all their stats. On death, Zombies may send out goo that acts like a Zombie bite. There is a small chance the Zombie virus may ocassionally mutate and become beneficial to it's host and greatly boost stats. This is denoted by the creature flashing red.
Black Square: A solid wall, impassable
Brown Circles: Food for Aliens and Humans, food does 3 things: increases strength, heals hp, and allows them to mate sooner.
Space: Switch Selected Object/Creature
Left Click: Place selected Object
Right Click: Delete Object under Cursor
P: pause and unpause the game. The game gets chaotic so this is a helpful option. You may still delete and add objects/creatures while the game is paused.