The extension port possesses five circuit points that a multipoint connector is soldered to. Beneath it is another eyelet that can also be used. (The multipoint connector is not included in all versions of the Game Kit).By use of the extension- port the Game Kit becomes usable like an Arduino Board. You can connect things that can then be controlled by the Game Kit. For example, you could fix a little motor to the Game Kit that vibrates when the player looses points. With additional hardware you could use the Game Kit to turn the lighting or the coffee- machine on and off. When you connect the Game Kit to the computer you can control these external device through your computer. In this scenario the Game Kit functions as the I/O- Board.

The other way round is possible, too. Sensors can be connected to the extension port. With a photo cell or a microphone you may control a game through an electric torch or a whistle.

Instructions and suggestions regarding the usage of the extension port are available from Mignon Kit Wiki and Arduino.