The objective of the game is to grow a cell, a circular player-controlled object, by swallowing both pellets and smaller cells without being swallowed by bigger cells. It can be played in a deathmatch or between teams. There is no set goal; players restart when all of their cells are swallowed.
The game contains three entities: pellets, cells and viruses:
Pellets, or food, are randomly scattered among the map. When swallowed, they slightly increase a cells mass.
Cells are controlled by players. Only opponent cells that are smaller can be swallowed; they can be swallowed directly, or by splitting, as described below. Cells move slower with heavier mass and gradually lose mass over time.
Viruses split larger cells into many pieces. Smaller cells can hide behind them for protection against larger cells. They can be fed to create another virus launched at a direction the player chooses.
Players can split a part of their cell, flinging one of the divided cells at the direction of the cursor. This can be used as a ranged attack to swallow other cells, to escape from a difficult situation, or to move more quickly around the map. Split cells eventually merge into one. Players can also release a small fraction of their mass to grow other cells or to feed viruses, which splits them when done several times.