The offense calls out one of 14 plays. Players then consult a shared Play Chart with 15 result columns to determine their desired result and then select one of 8 values in their "analog computer" -- a box with two selector wheels and a result window. The result (the sum of the 2 numbers) is display by opening a window to a 3rd door in the computer. Players view play result on the Play Chart and move the ball on the field contained in the game box. A quarter is equivalent to 15 plays.