So far I've created a class for one game type that manages the interaction with the UI and the state of the game itself. But for tracking how many of the subgames have been won, or for understanding whether the next game presented should be more or less difficult, are there arguments to be made for making a 'game engine' class? How does the engine communicate to the games? For instance, when a game is won, how is that information relayed to the engine? Is there a better or more common design?