Screw Your Neighbour is a trick taking game similar to Bridge but more similar to Spades (without partners). You receive your cards, decide how many tricks you expect to take, and bid. The problem is that the bidding cannot add up to the number of tricks available. The last person to bid may not bid to make the bidding even for the round. In other words, somebody's getting screwed.
Most often, Screw Your Neighbour is played with 4 or 5 people and one deck. The maximum number of cards is dealt to all players, leaving at least one card to decide what suit is trump. All players must receive the same number of cards. After all the cards are dealt, the trump card is placed face up in the middle of the table (or the top left of the card area in a Jao game). For more than 5 players, a second deck is used and cancellation rules then apply (see Cancellation, below). For each successive hand, one fewer card is dealt to all players, finishing with a hand where all players have 1 card.
Other variations where the hands then increase in size by 1 card back to the maximum or a different number of cards are decreased or increased are also possible. With multiple decks, games of up to 8 or even 9 or 10 people are possible. This game can go up to whatever limits people can stand.
Once the game parameters (especially when the game is declared to be over) are agreed to by all players (whether by democracy, implict agreement or by coersion), play begins.
A trump card is shown face up on the table after dealing is complete. If the trump card is not an honour (i.e. it has a value between 2 and 9) then trump is the suit of the trump card. If the trump card is an ace, 10 or face card, the hand has no trump. Trump works in the same way as other trick taking games. Aces are "high", and thus are the highest value card in their respective suit.
Once the dealing is complete, bidding begins to the dealer's left (shown in the list of players as the person underneath the dealer). The person looks at their hand and decides how many tricks they expect to (or might be forced to) take. They provide this number to their game client and bidding proceeds clock-wise (down the list of players).
The final person to bid, who is the dealer, cannot bid to make the bidding come out even. In other words, if there are 10 cards in each player's hand, and 9 tricks have been claimed, the dealer may not bid 1. Bidding in this way ensures at least one person gets screwed per hand, and provides the name of the game.
Play then proceeds from the person on the dealer's left and the hand is played out as per normal trick taking game rules.
When the hand is finished, each player who makes their bid exactly receives 10 points plus the square of their bid. A person who makes 2 tricks exactly recieves 10 + (2 x 2) = 14 points. A person who makes 0 tricks exactly receives 10 + (0 x 0) = 10 points. Each player who does not meet their bid exactly loses the square of the difference. A person who bids 4 tricks and takes 2 tricks loses (4 - 2) x (4 - 2) = 2 x 2 = 4 points. Scoring is handled automatically by the game clients.
The person with the highest number of points at the end of the game is the winner.
If more than one deck is used, it's possible that a card with the same suit and value is played twice (or more) during a hand. If this happens, both cards are said to "cancel". They are ignored when deciding who wins the trick. If the trick would normally go to the person who played one of the cards it now goes to the second highest value card (or the third, if the two seconds cancel, etc.) If all cards for the hand cancel, the same player begins play again and the fully cancelled trick goes to whoever wins this trick.
If jokers are added to the deal, they become a 0 (lower than a 2) of the led suit. If a joker is led, the suit is the suit of the next card played.