1. A method of enabling user interaction with computer software running in a computer system via: an interface surface containing information relating to the computer software and including coded data indicative of at least one interactive element relating to the computer software; and a sensing device which, when placed in an operative position relative to the interface surface, senses indicating data indicative of the at least one interactive element and generates at least one of movement data and position data, the movement data being indicative of the sensing device's movement relative to the interface surface, the position data being indicative of the sensing device's position relative to the interface surface; the method including the steps of, in the computer system: (a) receiving the indicating data from the sensing device; (b) receiving at least one of the movement data and the position data from the sensing device; (c) identifying the at least one interactive element from the indicating data; and (d) operating the computer software at least partly in reliance on at least one of the movement data and the position data, and in accordance with instructions associated with the at least one interactive element, wherein the sensing device is further adapted to store a sensing device identifier which is adapted to distinguish the sensing device from other sensing devices of the same type.