Say 20
Say 20 or Say 21 [two "games"] is a simple little number puzzle that challenges the player to figure out why he always loses.
 
The player and computer take turns counting to 20 or 21 - each saying one or two digits on a turn. The player who Says 20 or Says 21 wins. 

In "Say 20",  the Computer goes first; in "Say 21", the PLayer goes first. The pLayer always loses because the game is rigged.  The Player's challenge is to figure out how the game is rigged and how it can be won.
Say 20 or Say 21 -  a little number puzzle that you can't win ==>  Why?