Full rules
The table
You sit south. North, across from you, is your partner; West and East are the opposing pair. All 52 cards are dealt out, thirteen to each seat, and the hand lasts thirteen tricks. Your partner’s cards stay hidden from you — you never see a hand but your own, which is what makes the bidding a judgement rather than a calculation.
Bidding: how many tricks will you take?
Before a card is played, every seat says how many of the thirteen tricks it expects to win. Your bid and your partner’s are added together into one contract, and the team either makes that total between you or loses it together. That is the reason an extra trick from your partner covers one you missed, and the reason nobody has to be exactly right on their own.
Judging your hand
Aces win tricks almost wherever they sit. Kings usually win if you hold a second card in the suit to protect them. Spades are worth more than their face value because they beat every other suit — and a long spade suit keeps winning after the short ones have run out. Being void in a suit is worth a trick too, as long as you still hold trumps to cut in with. The number suggested on screen is that arithmetic; feel free to overrule it.
Nil: bidding to take nothing
Bidding Nil is a promise to win no tricks at all. Make it and the team scores 100; take even one trick and it loses 100. It is worth going for on a hand with no aces, no unprotected kings and no high spades — and your partner keeps bidding normally, so their contract is scored separately from your Nil.
Following suit
Whoever leads plays any card they are allowed to, and everyone else must play that same suit if they hold it. Only when you are out of the suit led may you play anything else. This is the rule newcomers most often miss, so cards you are not allowed to play simply cannot be picked up, and the line above your hand says why.
Spades are trumps
A spade beats every card of every other suit, however small the spade and however high the other card. But spades cannot be LED until one has already been played on some other suit — “breaking” spades — unless spades are the only cards a player has left. That restriction is what stops the first player from simply cashing trumps from move one.
Winning a trick
When all four cards are down, the highest card of the suit that was led wins — unless somebody could not follow suit and played a spade, in which case the highest spade takes it. The winner leads the next trick. Every trick tells you who won it and why, so the rules land while you play rather than before you start.
Scoring
Make your team’s combined bid and it scores ten points for each trick bid. Fall even one trick short and you lose ten points a trick instead — bidding four and taking three costs 40, no matter how close it was. Nil is scored on its own at plus or minus 100.
Bags: why bidding low has a price
Every trick you take beyond your bid is a “bag”, worth one point at the time. Collect ten bags across the game and 100 points are taken off. So deliberately underbidding to be safe is not free — it quietly builds a penalty, and a nil bidder’s tricks count as bags for the team, which is why a partner who takes everything is not really helping.
How long a game lasts
One hand is thirteen tricks and runs a few minutes; it is the default here. Playing to 200 or 500 points is the traditional game and takes several hands, with the score, the bags and the same three opponents carried between them. Your game is saved if you close the tab.