When the insert was printed (in volume) for the first Mancala boards, the ideas was to include a "promo code" that would allow my customers to get a free copy of the mobile game I was about to write.
However, soon after releasing the game on the Google App store, I changed my mind about charging for it for anyone. So, ironically, the promo code is not really needed for anything.
I invite you to try the game!
The location in the app store:
The game is completely free and does not annoy you with advertisements or in-game purchases. Enjoy!