Easy. Cut up the squares into letter forms, and wire a switch to each individual letter. Address the switches from a computer bus and there's your control.
Easier said than done, natch...

I forget offhand the exact tech used in the originals, but Ben of Applied Science (on YT) has made faithful reproductions using modern inks (transparent, EL and conductive, in that order) with screen printing. Not the cheapest materials, but eminently doable!
Tim