Cooperation emerges when players ally themselves against other players in order to reach a common goal. Group
tasks are always present and required in team games (Gray et al, 1998) which are governed by rules. In team games,
levels of cooperation and competition vary and must therefore be moderated by rules to make sure that all team
members master the contents. For example, in the Earth Ball game, players are challenged by certain obstacles or
difficulties which can only be overcome by the pooling of player resources.