NIM game with 21 buttons.
Rule is :
This is a simple game called NIM. There are 21 buttons in the game field. What you have to do is avoiding select the final red circle! Each player must select 1-3 circles in a term. Who selects the final circle will lose the game. Each player has 15s to think and select. After selecting the circle, dont forget to press Go! to change player.
ENJOY!