- The players and cards
- The deal and play
- End of the game; scoring
- Notes on tactics
- Version with 6 Jokers
- Christiansen version
- Other variations
Zwicker (also known as Zwickern or Zwickeln) is a fishing game, played in Schleswig-Holstein in North Germany. The "Zwick" (equivalent to the English "tweak") is a play by which you capture all the cards from the table, scoring a bonus. There are several variants of Zwicker. The main description on this page is of the version taught to John McLeod and Günther Senst by Dietrich Jensen, who now lives in Hamburg but comes originally from the Dithmarschen region of Schleswig-Holstein. After this two variations are described - one using 6 Jokers played in Großenwiehe and Sillerup in Schleswig, as taught to Paul Eaton by Irmgard Ewald, and one that was explained to me by Reinhardt Christiansen, a Canadian whose parents came from Schleswig-Holstein. Finally there are notes on other variations described in German card-game books.
Note: Zwicker(n) is not to be confused with the similarly named Dutch game Zwikken nor with the Austrian game Zwicken - both of those are gambling trick-taking games played with a three card hand.
The Players and Cards
Originally, Zwicker was played with a normal 52 card deck but today jokers are usually added. Dietrich Jensen's version uses three distinct jokers, so that there are 55 cards in all. Before beginning the players must agree which is the large (25) joker, which is the middle (20) joker and which is the small (15) joker. If necessary the numbers 25, 20, 15 can be written on the face of the jokers to distinguish them.
This game is best played by four players in two fixed partnerships, partners sitting opposite. It can be adapted for two or three, playing as individuals, but the tactical possibilities of the game are then much reduced. The four-player partnership game is described here.
As in other fishing games (such as Casino and Scopa) there is a layout of cards on the table, and the objective is to capture cards from the table by playing a card of matching value from your hand, and when possible to clear all the cards from the table, thus scoring a bonus for a Zwick.
Each card has a matching value, used to determine which cards capture which. The matching values of the cards from two to ten are simply their face values. The remaining cards have matching values as follows:
|Ace||1 or 11 *|
|Jack||2 or 12 *|
|Queen||3 or 13 *|
|King||4 or 14 *|
* Aces, kings, queens and jacks have two alternative matching values. The matching value of each of these cards is chosen by the player who captures it, or captures other cards with it, or incorporates it into a build.
At the end of the play, the cards won by each team are counted. There are 3 points for the team that took the majority of the cards, but more important are the scores for certain valuable cards. The scoring values of the cards are different from their matching values:
|Large (25) joker||7 points|
|Middle (20) joker||6 points|
|Small (15) joker||5 points|
|Ten of diamonds||3 points|
|Ten of spades||1 point|
|Two of spades||1 point|
|Each ace||1 point|
|Majority of cards||3 points|
|Each Zwick||1 point|
So there are 30 points in all to be scored for the cards, plus one extra point for each Zwick.
The Deal and Play
Deal and play are clockwise. The first dealer is chosen at random. The dealer shuffles and the player to dealer's right cuts the cards.
Each hand is played in three stages. For the first stage four cards are dealt to each player, one at a time, and three cards face up on the table. The cards on the table are sometimes called the the Picture (das Bild). The player to dealer's left plays the first card and play continues clockwise. Each turn consists of playing one card from your hand face up to the table, which can be simply played and left there, or can be used to capture cards or to make a build. When everyone has had four turns, using up their first four cards, the dealer deals another four cards to each player. The game continues as before until the players run out of cards again, at which point there is a final deal of five cards each, which exhausts the pack. When everyone has played their last five cards the play ends and the hand is scored.
There are three possible things that you can do on your turn: to play a card which captures one or more cards; to play a card to form or add to a build; or simply to play a card without building or capturing.
Playing a card
The simplest thing you can do in your turn is just to play one of the cards from your hand face up on the table. It remains there and can be captured by another player later.
If you play a card that matches a card on the table (according to the matching values given above), you may (but are not forced to) capture the table card. If you decide to capture, you remove the captured card from the centre of the table and put it face down, along with the card you played, in the pile of cards won by your team.
If there are cards on the table whose matching values add up to the matching value of the card that you played, you can capture this group of cards - for example a 10 can capture a 7 and a 3, or the 25-joker can capture a king and an ace (11+14). Moreover if there are several separate single cards or groups which match the card you played you can capture any or all of these cards and groups. For example if the cards on the table are 3, 4, 7, 8, J you could play a 15-joker and capture either 8+7 and J+3 or 8+4+3.
You are never obliged to make a capture, nor to make all possible captures with the card you play.
Note that in serious play your partner is not allowed to point out capture possibilities which you may have overlooked - if you don't take all the cards you are entitled to capture, the remainder stay on the table.
If you capture everything on the table, leaving it empty, you score one point for a Zwick. You place one of the captured cards face up in the pile of cards you have won, so that the number of Zwicks scored by each side can easily be counted at the end. It makes the counting easier at the end if the face up card is not a scoring card.
Example: if the cards on the table are 2, 4, 6, 10, J and you play a jack from your hand you can count the jack you play as 12 and the one on the table as 2 and thereby capture all the cards on the table as two groups adding up to 12 (2+4+6 and 10+jack), making a Zwick.
After a Zwick, the next player of course has nothing to capture or build onto, so must simply play a card to the table. The following player can either capture that card, scoring another Zwick, or play another card to the table, and so on.
The third possible type of play is to make a build, which is a card or a pile of cards with an announced value and an owner. The owner must have a card that matches the value of the build, and must eventually capture the build unless it is first captured or modified by some other player. Normally you build for yourself, but if your partner has previously built a particular value and has not yet played the matching card, you can make another build of this value "for partner". Note that if you own a build, you do not have to capture it at your next opportunity - you can modify the build or make a new build, or make a different capture or even just play a card to the table. Your only obligation if you do not capture a build that you own is to keep in your hand a card which matches its value so that you can capture it later if it is left for you.
To make a single card build you simply announce the value as you play the card - if it is an ace, jack, queen or king you must fix its value at this point. For example if you have two queens in your hand you can play one of them announcing either "13" or "3". You are then obliged to keep the other queen to capture it, unless someone else modifies or captures it first. If you had just one queen and a three you could play the queen announcing "3", but not "13".
If you play a card onto an existing card or build you take over ownership and modify the old value by adding or subtracting the value of the card you play. To do this you must hold another card in your hand that matches the new value of the build you are modifying.
Example: if there is a 9 on the table and you hold 2, 7, A, you may play your 2 on the 9 and announce either "11" (by addition) or "7" (by subtraction). Alternatively, you could play your 7 on the 9 and announce "2". You cannot build your ace on the 9 - the result would have to be 8 (subtraction) or 10 or 20 (addition) and you do not have cards matching any of these values.
Another example: suppose that the 25-joker is on the table, and your partner has just played a queen, announcing 13. If you have a jack, when your turn comes you can build the jack on the joker, subtracting 12 and announcing "13 for partner", so that your partner's other queen can take your build as well, thus winning the joker.
Note that when building you can start a new pile or add to a single existing pile, but you can never combine separate table cards or piles into a single build.
If you build with a card which is equal to the previous value of the card or pile on which you play it, you have the extra option of leaving the value of the build the same. For example if you play a 10 on a 10 you can make a build of 10 (if you have yet another 10 in your hand) or you can make it 20 (if you have the 20-joker). Playing a matching card on a build and leaving the value unchanged does not prevent further modifications. (Note that this is different from the corresponding rule in Casino.) In fact any built pile continues to behave just like a single card build with the same value.
A built card or pile can be modified by any player, or can be captured alone or with other cards or builds.
Note that separate cards or builds on the table can only be captured by matching or addition, never by subtraction. Suppose for example that the table contains a build of 9, a build of 13 and a separate 4. If you play a queen, you can make a Zwick (13 and 9+4), but if you play a 9, you can only take the 9 build. There is no way that the 9 can take the 13 and the 4.
End of the game; scoring
Any uncaptured cards remaining on the table at the end of the first or second stage of the game remain there and are available for capture in the following stage.
If there are cards remaining on the table at the end of the third and last stage, they are all won by the last team that made a capture. This does not normally count as a Zwick. However, if the dealer's last card validly captures all the cards from the table leaving nothing, the dealer's team does score a Zwick for this.
At the end of the play each side then counts the value of cards they have won and their Zwicks; the two teams' scores should total 30 plus the number of Zwicks made. The scores are recorded and the turn to deal passes to the left. Zwickern is generally not played for money. If you play a series of hands, the overall winners are the team with the higher total score at the end.
Notes on tactics
The jokers account for more than half of the points, so much of the game centres around capturing or saving the jokers, and to a lesser extent the ten of diamonds. This is difficult because of their high matching values; they do not match any other single card.
You should avoid leaving cards totals of 10, 15, 20 or 25 on the table if the corresponding high value card might be held by an opponent. You do not want to let them save it easily by capturing a group of cards. If you hold a joker yourself, you will generally try to make a build to the value of your joker. The opponents will probably try to destroy this build, either by subtraction or by increasing it to match a larger joker that they hold, but your partner, knowing the joker you hold, may be able to restore it or make other builds to the same value on your behalf.
If there is a joker on the table - either because it appeared in the initial deal or because it has been played there - it can only be captured by building it down. If this does not happen it will eventually be collected by the team that makes the last capture at the end of the game. Even if you cannot build down yourself you may be able to do so by cooperating with your partner.
Example: If the 25-joker is on the table along with a 5 and you hold a queen and an 8, you can play your 8 on the 5 building 13. Now your partner knows that you have a queen, and may be able to play a jack on the joker, building 13 for you.
You should generally avoid leaving a combination of cards on the table that will allow your left hand opponent to score a Zwick. Not only does a Zwick score a point, but it puts your partner under pressure. It may be the start of a series of enemy Zwicks, your partner's card being matched by the right-hand opponent, and so on.
You should generally try to avoid playing aces, kings, queens and jacks except when capturing or building with them. If left free on the table they give the next player more options, because of their alternative matching values. In general it is bad to play low matching value cards to the table, as they are too easy to capture. Cards 5 to 9 give the next player fewer chances, especially if you have more cards of the same rank.
Zwicker with 6 Jokers
The version of Zwickern played in Großenwiehe and Sillerup, as taught to Paul Eaton by Irmgard Ewald, uses a 52-card pack plus 6 Jokers. 58-card packs of this form were sold as Zwicker cards from the 1950's onwards by the card-maker ASS from and were more recently available from Nürnberger Spielkarten.
The rules are similar to those of the Dithmarschen game described above with the following differences.
The Jokers have matching values 15, 17, 20, 22, 25 and 30. Since the Jokers as printed are not all distinguishable from their designs, the values need to be written at the tops of the cards before they are used.
The game can be played by 2, 3, 4 or 6 players. 4 or 6 players play as two teams, each player sitting between two opponents. The initial deal is two cards to each player, then five face up to the table, then two more to each player and five more to the table. So the initial table layout has 10 face-up cards and each player has 4. Subsequent deals are 4 cards to each player, two at a time, but no more to the table.
In the team game a player may ask a partner (Magger) whether they have a card of a particular value, and if they do, the player can then make a build of that value for partner.
All four Tens are scoring cards, and the larger Jokers are worth a lot more than in the Dithmarschen game: each scores just 10 points less than its matching value. The Joker scores are sometimes written at the bottom of each card. The scores are:
|Ten of diamonds||3 points|
|All other Tens||1 point each|
|Two of spades (Pingel)||1 point|
|Aces||1 point each|
|Majority of cards||3 points|
|Each Zwick||1 point|
So normally the total of the points scored by the players or teams is 83 plus the number of Zwicks. If there is a tie for most cards the 'cards' points are not awarded and the total is 80 points plus Zwicks.
Christiansen Version of "Zwickern"
This section was contributed by Reinhardt Christiansen, a lifelong Canadian, who learnt the game from his late father, formerly of Schleswig-Holstein. His mother's family also played a very similar version of Zwickern. Reinhardt played the game as a child in the late 1960s, and is no longer absolutely certain of all of the details of the game, especially the exact scoring, but has re-created the rules to the best of his ability below.
The Christiansen version of the game uses many of the same principles as the game described above, but introduces some important variations. The differences are as follows:
- It is played by two, three or four players as individuals.
- Four jokers are used, with matching values of 15, 20, 25 and 30. This results in a deck of 56 cards, the normal 52 card pack and 4 jokers. The 30 joker presents a special challenge: since no two non-jokers can add up to 30, it is clear that any building involving the 30 joker must involve another joker. For example, if the 30 joker is lying on the table, a player having a 5 and the 25 joker could use the 5 to build the 30 joker down to 25. Of course, another player could then build the 25 down to another value that could be taken by a non-joker, e.g. reduce the 25 to a 14 (King) by building it down with an ace (11).
- The number of cards dealt is different:
- Two handed version
- During the initial deal, each player gets 8 cards and 8 cards are dealt face up to the center of the table. In the second and third rounds, each player is again dealt 8 cards but no new cards are dealt to the Picture.
- Three handed version
- During the initial deal, each player gets 8 cards and 8 cards are dealt face up to the center of the table. In the second round, each player is again dealt 8 cards but no new cards are dealt to the Picture.
- Four handed version
- During the initial deal, each player gets 6 cards and 8 cards are dealt face up to the center of the table. During the second round, each player is again dealt 6 cards but no new cards are dealt to the Picture.
- The values of the cards are the same as in Dietrich Jensen's version above, with the exception of the jokers. The scoring values are:
Item Scoring value 30 joker 7 points 25 joker 6 points 20 joker 5 points 15 joker 4 points 10 of Diamonds (cardinal) 3 points 10 of Spades (honour) 1 point 2 of Spades (honour) 1 point Each ace 1 point Winning most cards 3 points
(not awarded if there is a tie)
Each Zwick 1 point
A Sample Game of Zwickern (Christiansen variation)
The following is an example of a game of Zwickern, played according to the rules of the Christiansen variation. It is annotated to highlight the reasoning behind each player's actions during the game.
Four imaginary players, Albert, Beatrice, Charlie, and Dianne are having a game of Zwicker. None of these players is especially gifted so each is capable of making poor plays when better plays are possible. Albert won the right to deal. After the deal for the first hand, the cards are distributed as follows:
Albert: A, K, J, 3 ; 10 ; Joker 15
Beatrice: K ; 8, 7, 3 ; 9, 5
Charlie: 8, 7, 3 ; J, 5 ; 6
Dianne: 9, 6 ; J, 10 ; 4 ; Joker 20
Picture: Q ; A, 8, 4, 2 ; 2 ; 10 ; Joker 30
The first hand is played out as follows:
- Beatrice is to the left of Albert and plays first. She sees that the Q and the A add to 14, assuming that they are valued respectively as 13 and 1 or 3 and 11, and that the 8, 4, and 2 also add to 14, so she takes both builds with her K. (She could have taken the 10 and 4 instead of the 8, 4, and 2, but she feels that the one extra card will help her chances of getting the bonus for having the most cards at the end of the hand.)
- Charlie is to the left of Beatrice and plays next. He sees that the 10 and the 2 add to 12, the value of a jack, so he takes these cards with his J.
- Dianne is to the left of Charlie and plays next. Dianne sees that the only card left on the table is the Joker 30. Fortunately, she has a Joker 20 and a 10. She plays the 10 on the Joker 30 and announces that it is now worth 20. She can only do this because she has a Joker 20. If she was missing either the Joker 20 or a 10, she could not build the Joker 30 down. In other words, a player can only build a card up or down to a value that he has in his own hand. (Dianne could have played her Joker 20 on the Joker 30 and made the result a 10 but she reasoned that it was safer to make the build a 20 than a 10: she knows that she has the only card worth 20 whereas there are four 10s (one of which she has and one of which has previously been taken) in the deck, so she opts to make the build a 20 rather than a 10. In either case, there is a risk that another player could build the 10 or 20 up or down to something that she doesn't have and can't build up or down herself.)
- Albert is the next to play. He sees that he has no two cards that add up to 20 so he can do nothing but discard something from his hand. He discards the 3 into the picture.
- Beatrice also has no pair of cards that add up to 20 so she can do nothing about the Joker 30 - 10 build. She uses her 3 to take the 3 discarded by Albert.
- Charlie also has no pair of cards that add to 20 so he can only discard something from his hand. He discards the 3.
- Dianne plays her Joker 20 on the Joker 30 - 10 build to take it. Charlie's 3 is still on the table so she does not get a Zwick.
- Albert plays his J on the 3, declaring that the build has the value 15.
- Since Albert obviously has a Joker 15, which would be worth 4 points in final scoring, Beatrice decides to reduce the chance that he can use it. She plays her 8 on the 3-J build, declaring that its value has now been reduced to 7.
- Charlie plays his 7 to take the new build off the table. This clears the table and makes a Zwick. He chooses one of the cards that he has taken, a card which is worth no points, and leaves it face up in front of him to indicate his Zwick.
- There are no cards in the center of the table so Dianne must discard something from her hand. She chooses to discard the 4.
- Albert knows that his K is worth 4 or 14. He uses it to take the 4 on the table. He also marks a Zwick.
- Beatrice has no choice but to discard something from her hand. She discards the 7.
- Charlie has no seven and he has no pair of cards that add up to seven so he knows he must discard something. He knows that if he discards his 8 and that if Dianne cannot remove either the 7 or the 8 from the table in her turn, Albert will be able to take them with his Joker 15. He wants to avoid that so he discards his 6.
- Dianne has no Queen, which has a value of 13, so she can't take both the 7 and the 6. She takes the 6 on the table with her 6, leaving the 7 alone on the table.
- Albert can do nothing so he discards his A. (He chooses the A because it is worth fewer points than either the Joker 15 or the 10. The other players still have two cards each and he doesn't want anyone to be able to snap up these two valuable cards if he can prevent it. He prefers to play these cards as late as possible in the belief that they will then be left on the table until the next hand when he has more cards and has a better chance to take them himself.)
- Beatrice can't take either of the cards on the table so she discards her 5.
- Charlie has two possible moves: he could take the 5 with his 5 or he could take the 7 and the A with his 8. Since going after the A and 7 will result in him taking three cards rather than two, thus increasing his chances of having the most cards at the end of the game, and since the ace will be worth a point at the end of the game, he chooses to take the A and 7 build with his 8.
- Dianne can do nothing so she chooses to discard her J.
- Albert plays his 10 on the 5, declaring that the build is now worth 15.
- Beatrice can do nothing so she discards her last remaining card, the 9.
- Charlie can do nothing so he discards his 5.
- Dianne takes the 9 with her 9.
- Albert takes the 5-10 build with his Joker 15, leaving the J and the 5 on the table for the next hand.
All of the players have exhausted their cards so Albert deals out the remaining cards in the deck to the players so that each of the four players has 6 cards. At the conclusion of this deal, the cards are as follows:
Albert: A, 10 ; 9, 6 ; 7 , 3
Beatrice: J, 9 ; 5, 2 ; 8, 2
Charlie: A, 4 ; 6, 5 ; Q ; Q
Dianne: K, 7 ; K, Q, 4 ; Joker 25
Picture: J ; 5 (left over from previous round)
- Once again, Beatrice plays first. She takes the J with her J.
- Charlie takes the 5 with his 5 and marks a Zwick.
- Dianne discards her 4.
- Albert places his 7 on the 4 and declares the build to be worth 11.
- Beatrice has no single card worth 11 (i.e. she has no ace) but she sees that she has a 9 and a 2 which add up to 11. She plays her 2 on the 4-7 build, declaring that it is now worth 9. (She could have played the 9 on the 4-7 build and declared that the build now had a value of 2 but that would have been riskier because there are four 2's, each of which is worth 2, and four jacks, each of which can be worth 2, so she felt it less likely that someone else would have a card worth 9 than a card worth 2. She could have used either her 2 or her 2 but she knows that the 2 is worth a point during scoring while the 2 is worthless so she chooses the 2.)
- Charlie plays his 4 on the build, declaring that the build now has a value of 13 (i.e. a Queen).
- Dianne uses her Q to take the build and marks a Zwick.
- Albert discards his 3.
- Beatrice plays her 5 on the 3, declaring the build now worth 8.
- Charlie decides to use one of his Queens as a three and places Q it on top of the 3-5 build, declaring it now worth 11.
- Dianne sees her opportunity and plays her K on the 3-5-Q build, declaring the build now worth 25, the value of her Joker.
- Albert can do nothing and discards his 6.
- Beatrice can do nothing about the 3-5-Q-K build so she plays her 2 on the 6, declaring that the build is worth 8.
- Charlie can do nothing about the 3-5-Q-K build so he plays his Q on the 6-2 build and declares it now worth 11.
- Dianne stuns everyone by playing her K on the 6-2-Q build and declaring it also worth 25.
- Albert can do nothing about either build and discards his 9.
- Beatrice can do nothing about either build so she takes the 9 with her 9.
- Charlie can do nothing about either build so he discards his 6.
- Dianne takes both of the builds that add to 25 with her Joker 25, leaving only the 6.
- Albert can do nothing about the 6, so he discards his 10.
- Beatrice can do nothing about either of the cards on the table so she discards her 8.
- Charlie can do nothing about any of the cards on the table so he discards his A.
- Dianne uses her 7 to take the 6 and the A.
- Albert can do nothing so he discards his A. The game ends with the A, 10, and 8 on the table. Since Diane took the last trick, she is awarded these cards but is not awarded a Zwick because she did not take them with a card from her hand.
The players begin to score their hands, beginning with Beatrice:
- Beatrice: She took 12 cards altogether but the only one that was worth anything was the A, which is worth one point. She had no Zwicks. Her total score for this hand is 1 point.
- Charlie: He also took 12 cards. The only card he took that has a score value is the A, which has a value of one point. He also had two Zwicks which are worth one point each. His total score is 3 points.
- Dianne: She took 27 cards, which is the most that anyone took, so she gets three points for that. The cards which had value were: the 10, worth one point; the 2, worth one point; the A, worth one point; the A, worth one point; the Joker 20, worth 5 points; the Joker 25, worth 6 points, and the Joker 30, worth 7 points. She also had one Zwick, worth 1 point. The total for her hand is 26 points.
- Albert: He took only 5 cards. The cards which had value were the Joker 15, worth 4 points, and the 10, worth 3 points. He also had one Zwick, worth 1 point. His total score for this hand was 8 points.
Dietrich Jensen told us that at one time Zwicker was played without jokers, and such a game is indeed described in Das Buch der Spiele by Robert Hülsemann (Hesse & Becker, Leipzig, 1930). The same version reappears in two later books: "Einmaleins der Kartenspiele" by Rita Danyliuk (München, 1972) and "Das neue Spielbuch" by Rudolf Dietze (Berlin, 1984).
This is a much simpler game played by two or more people as individuals. The Aces and picture cards always have their higher matching values Ace=11, Jack=12, Queen=13, King=14 and building is by addition only. Players do not need to have a card matching the value of their build, but builds of more than 14 are not allowed since they could never be captured. The most valuable card is the Ten of diamonds or Cardinal which is worth 10 points. The Aces score 2 points each, the diamond-7 and spade-7 score one point each, and there is one point for the majority of cards (not awarded in case of a tie). This makes a total of 21 points for cards, in addition to which each Zwick scores 3 points. The initial deal is four cards to each player and four face up to the table to form the "picture". When the players have played their cards, another four each are dealt but no more to the picture. If there are more than 4 players a double pack can be used, for a total of 41 points plus Zwicks.
It is doubtful whether this old-fashioned version of Zwicker is still played, except perhaps by people who have learned it from a book. All the players from Schleswig-Holstein that we have encountered play the modern version with dual values for the Aces, Kings, Queens and Jacks, building by subtraction as well as addition, and Jokers with high matching and scoring values.
Claus Grupp's book "Schafkopf Doppelkopf" (Falken/ASS, 1976) describes a form of Zwicker that is similar to Hülsemann's. However, Grupp acknowledges that Zwicker is now usually played with Jokers added to the 52-card pack, and says that the Jokers are wild cards which can take on any value from 2 to 14 at the choice of the player. He retains Hülsemann's deal of four cards each to the players and four face up initially, and subsequently four to each player, but because of the larger pack this does not use all the cards exactly. Grupp deals with this problem by saying that in the last deal the cards care dealt one at a time as far as they will go, and that some players may receive one fewer card than others, so that the dealer will not necessarily be the last player. We have never found any players in Schleswig-Holstein who use the Jokers as wild cards or who deal unequal hands in the last round in the way that Grupp suggests. It seems likely that Grupp, not knowing how the Jokers were really used, invented the wild Jokers rule and grafted it on to Hülsemann's rules to explain the existence of the 58-card pack. In the resulting game the Jokers are too powerful, and Grupp evidently realised that this was a problem as he suggests several optional variants in which the power of the Jokers is restricted. Players may agree that a Joker on the table can only be matched by another Joker, or that a Joker can never be captured from the table. Also that clearing the table by playing a Joker does not count as a Zwick. Grupp's version of Zwicker was used as the basis of the English description of Zwicker in David Parlett's Penguin Book of Card Games (2000 edition).
You can download a freeware Zwickern program from Thanos Card Games.