1. A method for execution probability based server-to-client transmission of game code, comprising: operating a computer to receive a current game state of a game being executed on a client computer system from a subset of game code; determining respective probabilities for advancement from the current game state to a set of possible later game states; prioritizing game code required for the set of possible later game states in accordance with the determined probabilities for advancement from the current game state to each of the set of possible later game states; and transmitting game code required for the set of possible later game states, in order of the prioritized game code, from a sever computer system to the client computer system.