Leyden is a university city in South Holland and also the name of a two handed version of the domino game Matador. The main description on this page was contributed by Joe Celko. Günther Senst, who has contributed the slightly different version described under variants, says that the game is or was popular with students.
The game uses a double six domino set and two players.
Each player gets a hand of six tiles each and the remaining sixteen tiles form the boneyard.
The player with the lowest double, not including the [0-0], leads that double to start the first round. After the first round, the loser of the previous round gets the lead and must lead a double other than the [0-0]. If he refuses the lead, then the other player can lead again. If both players refuse to lead a round, then all the tiles are re-dealt. (Note that the starting player can draw extra tiles from the boneyard to obtain a double before playing.) The first double is the spinner for the round. The next two plays must be on the sides of the spinner, so all four arms are started.
There are four special tiles, called Matadors or "wild cards", which total seven pips each ([1-6], [2-5], [3-4]) or to zero ([0-0]), which I will discuss shortly.
Tiles are played on the arms of the spinner, but the rule for adding a tile to the end of the spinner is that the end of the arm and the end of the played tile must total to seven (1 and 6, 2 and 5, or 3 and 4). Likewise tiles played on the sides of the spinner must total to seven.
Doubles are played in line, and not across the arm, and have no special rules as in other games. A Matador can be played on any end of the arm without regard to the rule of seven. A Matador can be placed with either end of the tile in line or it can be placed across the line. A consequence of these rules is that a zero on the end of the arm cannot be played upon by any tile other than a Matador.
If the Matador is played in line, then the end of the arm is the open end of the placed tile. If the Matador is played across the line, then the end of the arm is either of the ends of the Matador at the choice of the next player.
Obviously, there is no reason to play the [0-0] across the line of the arm. And with a little thought, you will realize that the next tile placed after a Matador must be played in line.
A player can choose to draw as many tiles as he wish in his turn, but he must leave at least two tiles in the boneyard. A player who has no play must continue to draw tiles until either he has a playable tile or the boneyard is reduced to two tiles, which nether player is allowed to draw.
The game ends when someone dominoes or the round blocks.
At the end of the hand, each player gets the total number of pips in his hands. The first player to reach 100 is the loser. If both players go over 100 in the same round, then the lowest score wins. If both players tie at or over 100 points, then nobody wins.
The strategy is to try to hold two strong suits which total to seven, such as the 2' and the 5's. The blanks are important because they can be used to force opponent's Matadors or to block off an arm. This makes the [0-0] the most valuable piece, since it gives you both a guaranteed play and can be used to block one end of the arm.
The Matadors can change the end of the arm to any value, so it is a good idea to hold them until you either wish to block an opponent by making the end of the arm something he does not have in his hand, or to give yourself a way to place tiles that do not match to one of the ends of the arm.
Do not go crazy drawing tiles. Getting stuck with a big hand will cost you points.
On the German edition of this page Günther Senst describes a variant that differs from the above game as follows.