The Digi-Comp II was a toy computer invented by John "Jack" Thomas Godfrey (1924–2009) in 1965 and manufactured by E.S.R., Inc. in the late 1960s that used 1⁄2 inch (12.5 mm) 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 platform measures 14 by 28.5 inches (36 cm × 72 cm).