1. A method, comprising: detecting an image of one or more skeletal body portions against a substantially stationary background via an image sensor; segmenting the image into skeletal body portion areas and background areas; at intervals, counting a number of independent areas of the background, wherein each part of the background that is visually independent from other parts of the background is defined as an independent area, each independent area being visually separate from the other parts of the background by at least a part of the skeletal body portion areas; associating a control parameter for manipulating a displayed image on a user interface with a predefined region of each counted independent area; and changing the displayed image via the control parameter in relation to each change in a shape and/or a position of the independent area associated with the control parameter.