A light bulb includes a base; a light guide having opposed major surfaces between which light propagates by total internal reflection, a light input edge, and two light output regions of different optical characteristics at least one of which is associated with a corresponding one of the major surfaces; and a light source electrically coupled to the base and located adjacent the light input edge. The light source and the light guide are variably positionable relative to one another to vary a location on the light input edge at which light is input to the light guide such that light is emitted from the light guide selectively apportioned between the light output regions so that a characteristic of the light output from the light bulb is modified based on the optical characteristics associated with the light output regions and the relative positioning of the light source and the light guide.