a computer , such as a pc , includes a memory having an imaging program stored in it and a display unit , such as a raster scan crt are all operatively connected together so that the computing unit can generate a signal that will result in an image being displayed on the display unit . the image includes a moveable figure that moves in response to inputs being provided via an input terminal , towards a set of targets . in response to the inputs from the input terminal , the computer initiates a set of actuators to move the figure wherein each actuator defines the movement in a given plane .