The Digi-Comp II was a toy computer invented by John Thomas Godfrey  and manufactured by E.S.R., Inc. that used marbles rolling down a ramp to perform basic calculations. A two-level masonite platform with guides served as the medium for a supply of marbles that rolled down an inclined plane moving plastic cams as they went. The plastic cams played the part of flip-flops in an electronic computer - as a marble passed one of the cams, it would flip the cam around - in one position, the cam would allow the marble to pass in one direction, in the other position, it would cause the marble to drop through a hole and roll to the bottom of the ramp.
The Digi-Comp II was not programmable, unlike the Digi-Comp I, an earlier offering in the E.S.R. product line that used an assortment of plastic slides, tubes, and bent metal wires to solve simple logic problems.