"Scott F. Hall" wrote: A 1968 book, "Game Playing with Computers" by Donald D. Spencer has a good description of the logic behind the game. The basic secret of winning is to always present your opponent with an even position. To determine an odd or even position, convert the number of coins in each row to binary, i.e.: 5 Pennies 101 4 Nickels 100 3 Dimes 011 Add the columns. An even position is described if *each* column adds up to zero or an even number; otherwise the position is odd. In the above case, it is an odd position. The left column is even (1+1+0), the second column is odd (0+0+1) and the third column is even (1+0+1). The exercise of converting the above explaination to a mechanical device is left as an exercise for the reader :).

At 07:47 AM 4/13/00 -0500, you wrote: In this case, what you see is what there is. And I can say that with some certanty since the object in question resides about three feet away from my current position. There are no hidden springs or rubber bands used on Dr. Nim. Like the Think-A-Dot and DigiComp-2, it is cycled totally by gravity and the weight of the marbles. The mechanisms in all three show some commonalities in their designs. Along that line, I've been tinkering with an 8 foot tall (!) version of the DigiComp-2 using billiard balls to display at VCF IV. B^} -jim --- jimw(a)computergarage.org The Computer Garage - http://www.computergarage.org Computer Garage Fax - (503) 646-0174