PLAYERS, CARDS AND DEAL

Trex is played by four people using a standard international 52-card pack without jokers. The cards in each suit rank from high to low: A-K-Q-J-10-9-8-7-6-5-4-3-2. Deal and play are counter-clockwise.
To begin the session, the cards are shuffled, cut (by player to left of dealer) and dealt out to the four players, one at a time, so that each player has 13 cards. It does not matter who deals first, but the player who is dealt the 7 of hearts in this first deal is said to "own the kingdom." This player chooses which contract to be played each hand, and is also the dealer for the next four deals. During his or her "kingdom" a player may choose to play any contract based on his or her cards. There is no rule for playing the contracts in a set order, and there are 120 possible combinations of contract orders.
After the first dealer has played all five contracts, the kingdom passes to the player to his right, and so on. In some variations the game passes to the right first two times, then to the person opposite of the second player then to the remaining player. Each of these players, during their kingdoms, must deal five times, choosing a different contract each time, without repetition. After the four kingdoms are complete, 20 deals have been played, every player has chosen every contract once: the game is over.

THE FIVE CONTRACTS

Four of the five contracts are trick-taking games in which the aim is to avoid taking tricks, or particular cards. The dealer always leads to the first trick, and the winner of each trick leads to the next. Players must follow suit if they can, and the highest card of the suit led collects the trick.

King of Hearts

The player who takes the trick containing the king of hearts is reduced 75 points in standard setting. If the player doubling the card fails, and collects it, he or she is reduced 75 points. Oppositely, If another player collects it when it is "doubled" he or she is reduced 150 points (double the standard value) and the player who originally had it gets 75 points.
One common strategy followed in the pursuit of forcing the card's holder to collect it him or herself is for players to purposely lead hearts when possible.
If this contract is chosen and a player holds either the king of hearts alone, the king of hearts and the Ace of hearts, he or she may request that the hand be re-dealt. This is because such a player would most probably collect the card, which would be unfair for him or her! The player making the appeal should show all his or her cards to the other players. If this happens the replayed contract does not have to be King of Hearts.

Diamonds

Each card of the diamond suit taken in a trick takes 10 points off the running total of the collecting player.

Girls

Each queen taken in a trick costs the collecting player 25 points. Queens are stored face up in front of the winner of the trick in which they were played.

Collections/Lutoosh

Each trick taken costs the collecting player 15 points.

Trex or Trix

Despite its name, this is the only contract that is not a trick-taking game in the normal Western sense of the term. It is similar to Fan Tan or Card Dominoes. Players try to get rid of their cards as soon as they can by playing them to a layout, which begins with the jacks, and continues upwards in each suit to the ace and downwards to the two. The dealer begins and play continues counter-clockwise. At your turn you[who?] must play one card if you can. Legal plays are: any jack, or any card that is one rank higher or lower than a card that has already been played. If you are unable to play, you pass. The first player who runs out of cards scores plus 200 points. The others continue playing and the second scores plus 150 points, the third plus 100 points and the last gets plus 50 points.

Scoring

After 20 deals, when all four players have completed their kingdoms by choosing all five contracts, the game is over. The final scores indicate the result - the players with positive scores win by that amount, and the players with negative scores lose similarly.
The total points available in the five contracts are -75, -130, -100, -195, +500, so the total scores at the end of each kingdom and at the end of the whole game are always zero.