Breeder is a single-player game of population control. Organisms are constantly attempting to come into contact with one another. If they touch, they multiply. The player’s goal is to kill or repel the organisms and stop them from multiplying
Players influence the chaos of the game with a mouse interface. By holding down the mouse button, the player creates a bubble that grows larger over the course of a few seconds. When the player releases the button or moves the mouse, the bubble bursts, repulsing nearby organisms and killing one. If the bubble was at its maximum size, it kills additional organisms. By repulsing or killing the organisms, the player disrupts their flocking and breeding, slowing (but never quite stopping) their proliferation. Repulsed organisms are disoriented, unable to flock or breed, until they come to a halt.