On top of the model rested a stylus—just a black stick pointed on 
one end—and a palette, covered with a color wheel and other controls. 
Nell picked them up, touched the tip of the stylus to a green area on the 
palette's color wheel, and drew it across the surface of the model. A glowing 
green line appeared along the track of the stylus, disfiguring an ad panel for 
an airship line.