1. Interactive, electronic game apparatus for playing a game in which game characters appearing on a display are responsive to inputs from a game user, said apparatus comprising: a visual display presenting an observable state of said game and of said game characters to said game user in response to a display signal, an input device for interactively entering user input signals representative of user interaction with game characters, and processing means receiving said user input signals from said input device and generating said display signal and outputting said display signal to said visual display, said processing means including an extensible plurality of independent character behavior controllers for determining the behavior of respective said game characters, each said character behavior controller containing independent behavior logic to determine states and state transitions of its respective game character as represented to said user by said display means, said character behavior controllers being responsive to said user input signals and to game control signals for adjusting the behavior of said respective game characters, a game controller for coordinating the behavior of said game characters, said game controller containing logic to determine consistent game states for said game and said characters, and communicating said game control signals to said character behavior controllers so that the state of said game and of said game characters is a consistent game state, an operating application for operation of said character behavior controllers and said game controller on said processing means, each said character behavior controller including an independent dynamically-linked procedure invoked by said operating application, said game controller including logic to add new character behavior controllers to said game.