Games embody a special sort of reference: an in-between sort. This requires that game rules reference neither too strictly nor too loosely. The latter sort of reference transforms games into toys, ultimately referencing only the ego of the player. The former, stricter sort of reference turns games into simulations, where referencing becomes overly restrictive, bound by material and measurable concerns, dominated by a common (and often communal) set of values and beliefs. This chapter distinguishes the obligatory algorithms of simulations from the voluntary rules of games.