I've only played this a little, and it's from memory, so there may be omissions. In particular, I have not played the three-player version.

Mü uses a special deck of 60 cards, containing 5 suits of 12 cards each. Cards in each suit are numbered 0 to 9; there are two 1s and two 7s of each suit. In addition, each card is worth 0, 1, or 2 points toward a certain target, as marked by triangles on the edges of the cards. 1s and 9s are worth 0; 6s and 7s are worth 2, and the rest of the cards are worth 1 each, for a total of 60 over the entire deck.

A hand begins with an auction, which consists of players, in turn, either bidding by exposing one or more cards from their hand face-up on the table, or passing. The **quantity** of cards exposed represents the value of the bid; the suits and values of the cards have a more subtle meaning. If the auction ends with two or more players tied for having bid the most cards, then the hand ends without being played; and whoever caused the bid to be tied suffers a penalty. Otherwise, the player who bid the most cards becomes the chief, and, among the other players, the one who bid the most cards becomes vice. For the purposes of determining the vice, only, ties are broken by the highest valued cards bid (so 9 beats 8, or 8-6-6-1 beats 8-6-5-4). If there is still a tie, the hand is played with no vice.

The vice (if there is one) begins by choosing a trump. In Mü, any suit or any number can be trump. So the vice could choose blue or red or 7s or 0s. This becomes the low trump. Then, the chief chooses a partner (in games with 4 or more players) and a second trump. Because of all the possibilities for trumps, the trump suit can get complicated. There are 3 possibilities, listed in order of increasing complexity:

- There is no vice. In this case, there is a simple trump suit, chosen by the chief.
- Two suits or two numbers are chosen as trump. In this case, all the cards in the trump chosen by the chief outrank all the cards in the trump chosen by the vice. If suits are chosen, then the cards within each suit are ranked in their usual order; if numbers are chosen, all cards of the same number are equal.
- One suit and one number are chosen. In this case, the highest ranking cards are the double trump(s), the cards which are both in the suit and the number chosen. If 7s and red are chosen, the two red 7s are the highest trumps. Next come all the other cards in the trump chosen by the chief, and finally the remaining cards in the trump chosen by the vice. All cards in the trump number are ranked equally, wherever they fall, except for the double trump which is always highest.

During the play of the hand, you must follow suit (keeping in mind the jumbled definition of suits due to trumps) if possible; otherwise, you may play anything (trump or otherwise).

If there is a tie for the highest card played to a trick, (two 7s or 1s in the suit led, or two trumps with the same number and not distinguished by their suit) then the first card played (among the tied cards) wins.

At the end of the hand, each player counts up the number of points (triangles) on cards in tricks he won, and scores that many points. In addition, the chief and his partner have a goal, based on the value of the chief's bid; if they make it, they each score a bonus based on the value of the bid and the number of cards in the trump chosen by the chief. If they fail, only the chief loses an amount based on how far they missed their goal.

Game is played to 200 points.