This is a variation on the basic block game posted as an on-line game at http://www.wabmo.com/Homini/Lupus.html
The game uses a double six domino set.
Four players take six tiles each, leaving a boneyard of four tiles.
The player with the lowest double plays first and this becomes the spinner for the hand. Play moves clockwise. The tiles are matched end to end in the usual manner, and doubles are play at right angles to line of the train. However, doubles can be placed either face up or face down.
If the double is placed face up, play on that arm of the tableau continues in the usual manner. If the double is placed face down, play on that arm of the tableau stops. A player must show the double before turning it face down.
A player not able to place a tile in his turn draws tiles from the boneyard until he is able to play, or until the boneyard is empty. If a player is not able to play and the boneyard is empty, he loses his turn.
The hand ends when one player dominoes, or when the tableau is blocked. There are two types of blocked games. If no player can make a play on any of the four ends of the tableau, then the game is blocked. If all the ends of the tableau end with a face down tile, so nobody can play regardless of what they have in their hands.
At the end of the hand, each player counts the pips on the tiles remaining in his hand. The player who dominoed has a count of zero. Scores are calculated by summing the total number of pips in all four hands, dividing that number by four and subtracting the point in your hand, then mulitple by 100. This is how far above or below the average you were. Written as a formula:
For example, assume that player A, dominoed, player B, was holding the [0-5], player C was holding the [4-6] and player D had the [5-6]. The total numer of pips is (5 + 11 + 9 + 0)= 25 and 25 / 4 = 6.25
This formula means that the sum of all the player's scores is equal to zero.
The highest score at the end of a pre-arranged number hands is the winner.
The use of doubles to block the arms of the tableau is obviously the key point in this game. Because you can depend on the [0-0] being played at the spinner most of the time, an arm with a blank on its end is almost always immune from closure. As the arms are closed, each double has more and more power.