Agar.io Agar.io is usually the game most people think of when looking for browser-based games. In this MMO action game, players take control of a circular cell as it hunts to consume smaller static cells. Other players control rival cells which you must compete with for food – and if their cell is larger than yours is, then you run the risk of becoming their food if they catch you. This is where things get interesting: the larger your cell, the slower you move. So what do you do when you’re too slow to consume cells, but too small to absorb everything in sight? Cells can split in half at will, giving players two individual cells to control. Each cell can split up to four times, allowing players to escape certain death when dealing with a giant enemy. Agar.io’s highly addictive gameplay, in addition to its five unique multiplayer modes, make it one of the best io games.