According to at least some embodiments of the present invention: a user’s non-stationary exertion is detected; a virtual terrain is provided; and the detected non-stationary exertion is normalized for the virtual terrain. The techniques use the characteristics of the pixel display to determine the form of the barcode in the pixel display. Various types of lenses having a variety of purposes may be fitted or formed in the kit, including prescription lenses to suit the user for general use or for reading, sun-protection or safety lenses. According to the invention a foldable arm comprises means which facilitate the extension of the display from the first to the second position and from the second position to a further position.