In the late '50's Popular Electronics magazine (out of print) published an article "building a rudimentary computer" It was called the Challenger. It was a circuit that could play the old parlor game of "21", and utilized a mechanical stepping relay to do the "computing". There was a series of 21 pilot lamps, with a 'player' and 'machine' pushbuttons. The player, and the machine, in turn, could light 1, 2, or 3 lamps, with the object being to avoid lighting the last, or 21st lamp. The machine would invariably win. The secret is that within the number 21 there are five groups of 4, with one left over. Whatever number the player selects, (1, 2, or 3) the machine then selects a number that, when added to the players choice, totals 4. (player 1, mach. 3 / player 2, mach 2/ player 3, mach. 1) It would seem that today's processors and LED's, could handle this task easily. Would you, or someone you know, be interested in designing such a circuit as a project? I built it back then but I'm afraid my knowledge is stuck back in that time and would need instructions remenicient of that era.