Move your mouse below the horizon to change the location of the sphere. Click on it to make the sphere static and not follow the mouse. Click again anywhere on the stage to make the sphere follow the mouse again.
This was inspired from the perspective of the arts about drawing in 3D (not the rendering of 3D scenes using ray casters and all that, but by drawing in 3D by hand.) You may like to take a close look at the blended shading on the sphere, as well as the cast shadow below it, and notice how they are done carefully opposite the light source.
