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 a signature field relating to the computer software; and a sensing device comprising: (a) an image sensor adapted to capture images of at least some of the coded data when the sensing device is placed in an operative position relative to the surface; and (b) a processor adapted to: (i) identify at least some of the coded data from one or more of the captured images; (ii) determine an orientation, within the captured images, of at least some of the coded data; (iii) decode at least some of the coded data; and (iv) generate, using at least some of the decoded coded data: (A)indicating data indicative of the signature field; and (B) 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 signature field on the basis of 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 signature field.