The inhabiting organisms use vision as input to a neural network brain that employs Hebbian learning at its synapses. The outputs of this brain fully determine the organisms'behaviors. These organisms and all other visible constituents of the world are represented by simple polygonal shapes. Vision is provided by rendering an image of the world form each organism's point of view, and using the resulting pixel map as input to the organism's brain, as if it were light falling in a retina. A small number of an organism's neurons are predetermined to activate a suite of possible primitive behaviors, including eating, mating, fighting, moving forward, turning, controlling their field of view, and controlling the brightness of a few of the polygons on their bodies.
Organisms expend energy with each action, including neural activity.
They must replenish this energy in order to survive. They may do so by eating the food that grows around the environment. When an organism dies, its carcass turns into food, so they may also replenish their energies by killing and eating each other. Predation is thus modeled quite naturally. The organism's simulated physiologies and metabolic rates are determined from an underlying genome, as are their neural architectures.