The game consists of 21 coins in a bag (7 additional coins are used as positional markers).
Each coin bears two numbers ranging from 1 to 7 - one number per side. The two numbers are always different.
The coins are thrown on the table and then sorted by the visible numbers.
In his turn a player selects a coin, put it on his side of the table and flips it over.
The first player to reveal all seven numbers on his side of the table wins the game.
Since each coin bears exactly one of the (21) possible combinations of two different numbers from 1 to 7 the players gain more and more information about the numbers still hidden and thus are able to make - quite educated - guesses to select the correct coins.