Multiplayer long-running competitive games in which you kill/consume other players to become stronger, generally. Agar.io was among the first, and is mostly rep

Multiplayer long-running competitive games in which you kill/consume other players to become stronger, generally. Agar.io was among the first, and is mostly representative of the "genre" - people wrote a pile of clones, improvements, rethinks, etc, mostly with .io domains, so they wound up being called "io games".