RichMan

In 1957 Popular Electronics magazine (out of print) published a project article for a "rudimentary computer" that could play the old parlor game, "21". It utilized a five deck mechanical stepping relay to do the "calculation", and a series of 21 pilot lamps. A player, using a 'player button, could light 1, 2, or 3 lamps. A 'machine' button would then allow the machine to also light 1, 2, or 3 lamps. The object of the game was not to be forced into lighting the last, or 21st light. The machine would invariably win. The secret was based on the fact that there are five groups of four within the number 21, with one left over. (the 21st) Whatever number the 'player' selects, the 'machine' then selects a number, when added to the player's choice. totals four. (1 +3, 2 +2, 3 +1) It would appear to be a natural for modern day components such as processors, LED's, etc. Could anyone update such a project with a clear, understandable circuit for a non-engineer?