Skat is a
German trick-taking game for
three players. In skat, the winning
bidder (called
declarer) is playing against the other two players, usually trying to take tricks containing the majority of the points. Points are assigned to various
cards -- each
ace is worth 11, each 10 is worth 10, each
king 4,
queen 3, and
jack 2, for a total of 30 in each
suit or 120 in the deck. The game is played with a
short deck that only includes cards from 7 to ace (32 cards total).
The trump suit in Skat is a little irregular. Jacks are always the highest trumps, in the suit order of clubs (highest), spades, hearts, diamonds. Then under that, if a trump suit was chosen, are the cards in that suit, in this order: A, 10, K, Q, 9, 8, 7. This is also the order of cards within each non-trump suit. The one exception to all this is the Null game, where there are no trumps (not even jacks) and the card order is "normal" (A-K-Q-J-10-9-8-7).
At the start of each hand, each player is dealt 10 cards in packets of 3, 4, and then 3 cards (so as to avoid the evening out of suit distributions that tends to occur with incompletely-shuffled decks in trick-taking games). The two cards left over form the skat; these are initially placed face-down in the middle of the table.
The bidding is based on the values of possible contracts. Two players go back and forth until one player refuses to bid higher, and then the winner of these two and the third player bid starting from that point until finally there is a high bid.
The values of possible contracts are based on a suit value and a multiplier.
The suit is the trump suit chosen and the values are 9 for diamonds, 10 for hearts, 11 for spades, and 12 for clubs. There is also a suit option "grand" (no trump -- though Jacks are still trump) which has different values in different variations of the game. I learned "Texas Skat" where grand has a base value of 16, but others play 20 or 24.
The multiplier is based on a sum of several items. The most obvious of these is the number of "matadors", or top trump, either in or not in the declarer's hand. For this purpose, the skat is also considered part of the declarer's hand. For example, if the declarer has the top two trump, but not the third, he is "with 2". If the declarer is missing the top trump, but has the second-highest trump, he is "against 1". Regardless whether he is "with" or "against", this number is the first part of the multiplier. Then one is added to this, always (often spoken of as "for game"). Thus, the smallest possible contract value (and lowest possible bid) is 18 for with or against 1 in diamonds.
Add one to the multiplier for a schneider - taking 90 or more points. Add an additional one for an announced schneider - announced before the hand is played; failing to schneider then becomes a failed contract. Add one on top of the schneider bonus for a schwarz - taking every trick, and another additional one if schwarz is announced.
There are other variations such as not looking at the skat and playing with your hand exposed that add additional multipliers, but these are rare.
For example, a schwarz announced in clubs with 5 is scored as follows:
with 5
add 1 for game = 6
add 1 for schneider = 7
add 1 for schenider announced = 8
add 1 for schwarz = 9
add 1 for schwarz announced = 10
The base value for clubs is 12, so this hand is worth 120.
If the Null game is chosen, it is worth 23 points (20 in Texas Skat), and other weird values are used for the unlikely cases of Null with not looking at the skat or playing with hand exposed.
At the end of a hand, if it turns out that declarer's contract (made or not, but including bonuses for schneider and schwarz if these were made but not announced) does not match or beat his bid, he is set and loses double the amount of the smallest multiple of his base value that meets or exceeds his bid.
If the declarer failed to take the appropriate number of points, but the contract was sufficient, he is set and loses double the value of his contract.
Otherwise the contract is made and the declarer scores its value.