In this piece a digit lights briefly on each column, chasing around at about one turn per second.  Each time the number lights it shows a different value at random.  The speed varies slightly with the ambient light -- there is a small light sensor in the top center.

The numeric displays are quite attractive when not illuminated, looking somewhat like a Chinese ideogram.  This is why I chose to light only one digit at a time -- to show off the intrinsic beauty of the display itself.  These are an early 7 segment LED type that uses 2 LEDs per segment.