[bollcmpa] Blackjack as a speed arithmetic incentive

Play a game which has positive expected outcome for the player, so provides incentive to play it as rapidly and often as possible.  The game's mechanic could involve mental arithmetic, thereby providing incentive to learn to do mental arithmetic rapidly, so it is an educational game.

Blackjack is one possibility, except playing from the point of view of the house (the dealer).  The human dealer (representing the house) plays against one or more computer player/bettors and the card outcome of each game is shown.  The dealer has to sum the cards of each bettor's hand and decide whether to pay out.  Mistakes by the human that overpay a bettor do nothing special other than eat into the house's profits (which the human wants to maximize).  Mistakes which underpay a bettor are caught, the house must pay out, and maybe some other penalty like a time penalty which also eats into the house's profits because the house makes more money the more rounds are played.  (Even if blackjack played optimally is an exception to "the house always wins", we can still cause the house to win by having the computer bettors play less than optimally.)