Truf is the Indonesian word for English "trump", in the same meaning as when used in the term "trump card".
It is probably derived from a Dutch word. Used alone, Truf means a card game, an interesting one.
It is similar to Contract Bridge in the sense that Bridge is also a trick-taking game preceeded by bidding.
But that is where the similar ends. One of the most contrasting difference is that Bridge is partner-game, you
form partners with the player in front of you, and try to win the most tricks. Truf is a each-person-for-himself
game, and partnering is discouraged (to the point that it means cheating).
Truf is an exact trick-taking game. It consist of two phases: bidding phase, and playing/trick-taking phase.
During bidding, everyone bets on how much tricks they can take later on. This is called bidding, because the player
who bets the highest number of tricks, get the chance to define the trump. After bidding is completed, the trick-taking
rounds are started, and each player try to take as many tricks as they have bidded before - no more or no less.
At the end of the game, the number of tricks collected from each player is counted, and compared against their original bids,
and the scores is calculated based on this - the winner is always the one with the highest bid, and meets their bid,
not more, not less.
For a more thorough explanation, please refer to Truf Game Definition.
They have written a very clear explanation of how this game works.
However - please note though, every Truf game is different - for rules are determined and agreed by those who are playing.
These sets of rules, though similar, is not identical. The rules shown in the above link is just one of many and
by no means standard. JB Games houses Truf game with many different rules for your enjoyment. You can also suggest the kind of rules
you want, if you ask nice enough and if the condition permits, I may do it for you.
General
Minimum 3 players are needed to play the game, and maximum is 4 players.
Bidding
Any number of cards are possible.
Any combination of "plus" or "minus" cards are possible. Indicate "minus" card bid by highlighting the card
(a red border will be shown).
A single card bid will always be assumed to be positive.
Total bids less than zero will be taken as zero.
During bidding, cards have the following values:
Number cards: the number represents their values (from 2 to 10)
Ace has the value of 1
Picture cards (Jack, Queen, King) - in a single card bid, their bid value is zero. Otherwise it's 10.
The winner is the one with the highest bid. He/she gets to decide what's the trump.
The trump is decided based on the suit of the card used to bid. If more than one card is used to bid and all of them are of
the same suit, then that suit become the trump. Otherwise a no-trump game will be played.
If the bid value from players are the same, those with lesser number of cards win.
If the above doesn't resolve the winner, the one who has the highest card will win - in this case, cards are ordered as
(from highest to lowest): Ace, King, Queen, Jack, 10 ... 2, with Spaces is highest, followed by Hearts, Diamond, and
then Club.
In a 3-player game, the total number of tricks is 17. In 4-player game, the total number of tricks is 13.
If the total number of tricks bidded exceed the max total, the game is called as "high game" and the "high game" scoring mode
will be used.
If the total number of tricks bidded is less than max total, the game is called as "low game" and the "low game" scoring mode
will be used.
If the total number of tricks bidded is equal to the max total, the game is called as "even game" and the bid winner will have
to adjust the game up or down (adding or subtract a number of tricks from all players) to make it either high or low game.
Playing
The playing phase consist of eiher 13 (for 4-player) or 17 rounds (for 3-player) of trick taking.
The round is started by the bid winner, or by the previous round winner. This player is called as the "round leader".
The leader can play any card except trump card, unless: a) trump has been played before b) he has no other card to play
The other players normally play their turns following clockwise direction, though this is not imposed by the system.
The other player must play a card with the same suit with the leader card, unless he doesn't have cards of that suit
anymore, in which case he/she can play either: a) a trump card, or b) any other card
Trump card is played face down, and turned face up for evaluation when everybody has completed their turn.
Upon completion of the all player turns, the winner of the round is determined as follow:
Trump cards always win against other non-trump cards.
Non-trump cards that is of different suit from the leader card, always lose
The ranking of the card follows this (highest to lowest): Ace, King, Queen, Jack, 10, 9 ... 2.
The winner of the round is those with the highest ranking card.
Scoring
If the tricks you take equals to the bid you made, then your game score is your bid (except when you bid zero,
the score for meeting your bid is five (in 4-player mode), or seven (in 3-player mode).
If you don't meet your bid, your score is always negative. It's a matter of how bad it is.
In a high game - you lose 2 points for every trick you don't get, and you lose 1 point for every excess trick you take.
In a low game - you lose 1 points for every trick you don't get, and you lose 2 point for every excess trick you take.
In either case, if you bid zero, the first trick you get will always have negative 5 (or 7) points, with the rest following the
above rules.
Note
The above rules are enforced by the game engine, so you don't have to worry about making mistakes.