In one implementation, a method includes detecting, using a processor, user input through a camera lens. The method further includes determining, using the processor, that an identity of a user, selected from identities of at least two users, is associated with the user input. The method also includes tracking, using the processor, a local interaction between the at least two users based on at least the identity, the user input, and stored rules that govern the local interaction. The tracking can include determining whether the user has complied with the stored rules that govern the local interaction. Furthermore, the local interaction can include a multiplayer game.