A network game system includes a center server and game machine. The center server includes a first transmitter, which transmits, to the game machine, first data indicating a settled play amount out of a played amount which is represented by either an accumulated number or time period that a game program...http://www.google.com/patents/US7452277?utm_source=gb-gplus-sharePatent US7452277 - Center server, game machine, methods of controlling the center server and game machine, and network game system including the center server and game machine
