Stipple shading is used in the accompanying Figures to convey surface contouring, not texture. Features depicted using broken lines and a lack of shading indicate environmental structure that is unclaimed in various embodiments. For example, various logos and other text are shown in broken lines and with a lack of shading; in such cases, the unshaded regions around such logos or text are enclosed in a rectangular border that represents the boundary between a claimed portion of the depicted design and the unclaimed portion of the depicted design.