Christopher Strachey expanded a draughts program he had originally written in 1951 and ported it to the Ferranti Mark 1, which showed the state of the game on a CRT display. OXO and Strachey's draughts program are the earliest known games to display visuals on an electronic screen, though it is unclear which of the two games was displayed first. As it ran on a computing device and used a graphical display, OXO is considered under some definitions to be a contender for the first video game, though under others it does not due to its lack of moving graphics or graphics which update continuously. Interaction Each game was played by one user against an artificially intelligent opponent, which could play a "perfect" game. The player entered their input using a rotary telephone controller, selecting which of the nine squares on the board they wished to move next. Their move would appear on the screen, and then the computer's move would follow; the game display only updated when the game state changed. OXO was not available to the general public and could only be played in the University of Cambridge's Mathematical Laboratory by special permission, as the EDSAC could not be moved, and both the computer and the game were only intended for academic research purposes. References External links The Edsac Simulator — An emulator of the EDSAC developed by Martin Campbell-Kelly that includes OXO 1952 video games Early history of video games History of computing in the United Kingdom Puzzle video games Tic-tac-toe University of Cambridge Computer Laboratory Video games developed in the United Kingdom