A popular game played in Hong Kong Bars and Restaurants.
Now you can play it ... even in office :P
Closed Hand - counts 0
Opened Hand - counts 5
The Leading side guess the total counts of both players.
If the guess is correct, continues the guess. If the leading side make the 2nd correct guess, he/she win that round.
If the Leading side got a wrong guess, the other player will take the Leading role instead.