Kraken is a trick-taking game that is played by two teams of two players each. North/south form a team and east/west form the other team.
At the start of the game each player receives eight cards.
For the trump suit the card order and card score is:
Jack (20 points), nine (14), ace (11), 10 (10), king (4), queen (3), 8 (0), 7 (0).
For the non-trump suits the card order and card score is:
Ace (11 points), ten (10), king (4), queen (3), jack (2), 9 (0), 8 (0), 7 (0).
In the "double spades" variant these points are doubled when spades is trump.
This means there are 162 points in a game (324 when playing "double spades" and spades is trump). On top of this extra "roem" can be scored by taking tricks that contain a sequence of three cards (20 roem) or four cards (50 roem).
The special combination of Queen/King of trump scores 20 roem ("stuk").
Four tens, queens, kings or aces are worth 100 roem, four jacks is worth 200 roem!
At the start of each game the first player selects trump. The opponents are now allowed to "double" and play for double points (this is also known as "kraken", hence the name of the game). After doubling the first team is allowed to redouble. After a redouble the opponent team can decide to "superdouble", playing for 8 times the score.
After the double round each player in turn gets the opportunity to meld the roem in their hands. The player with the highest roem wins and only the winning team receives their melded roem. If players of opposing teams meld an equal amount of roem, the player with the highest roem wins.
The first player starts the first trick. The player that takes a trick starts the next trick. If you cannot follow suit you must play trump if you can.
You are not allowed to play a lower trump than a trump already on the table unless there is no other option.
If the team of the leader scores half the points or less they are declared "down" and loose all points including roem.
If the team of the leader takes all tricks they get 100 bonus points (this is called a "mars" or "pit").
If you cannot follow suit you have to play trump unless the current highest card in the trick is from your partner.
That's about it. Have fun!