'Strategic supplements' in games with polylinear interactions

Strategic games are considered where: every player chooses from a compact subset of the real line; the partners' choices affect each player's utility only through their scalar aggregate, which is affine in every single partner's choice; if the choices of all players but two are fixed, then both functions expressing the dependence of one player's aggregate on the other's choice have the same slope; the best response correspondence of each player is nonempty-valued and increases in the aggregate. Every such game admits a 'Cournot potential,' i.e., Nash equilibria exist and all best response improvement paths, in a sense, lead to them.