A printed interface for user interaction with a computer system via a sensing device is provided. The interface comprises visible graphical information and coded data readable by the sensing device. The coded data comprises a plurality of substantially undifferentiated marks positioned relative to a predetermined pattern, with an orientation target structure for allowing relative rotation of the predetermined pattern to be determined. The visible graphical information indicates an operation that the user can select and transmit to the computer system by reading the coded data with the sensing device.