X or C is a kind of abstract computer game which was programed and played by Peter Max and Robert Pravda using four Commodore 64 personal computers. Both of them live in Den Haag, The Netherlands. The game is based on the idea of using the keyboards as a musical instrument to create sound and colour pixels. Both players are equiped with preprogramed sequences of colour and sound which enables them to play against one another in real-time. The limited processor speed of the C64 is used as advantage. This is due to the fact that it causes interference in the sound and visuals, giving the audience the impression that an abstract animation film is created live.