How it works

The solver

Card play is judged by a double-dummy solver: DDS, the open-source engine by Bo Haglund and Soren Hein that much bridge software uses. Given all four hands, it works out how many tricks each side takes with perfect play from any point, and so which cards are best.

Its blind spot is that it never has to guess. Where a player must (which way to take a two-way finesse, whether to finesse or play for the drop), it already knows where the cards are, and on its own it calls the lucky card right. So at those moments, lessons go by the odds instead.

Coached lessons

• The hands. Some are written to teach one idea; others replay real deals from European team and youth championships and online tournaments, credited to their event. With Pro you can take a lesson on a hand of your own.
• You play one seat, and as declarer dummy's cards too. Between the coach's questions, the cards are played as they were at the table.
• Where the coach stops: at the turns where your card matters, where at most half the cards you could play are best, or where the card played at the table cost a trick.
• A guess is judged by the odds. Where the right card depends on cards you can't see, the lesson deals up to 400 layouts of the hidden hands that fit what you know: your hand, dummy, the cards played, who has shown out, and what the bidding showed. Each card you could play is tried on every layout, with the rest of the hand played perfectly. A card about as good as the best over those layouts is a sound play: it isn't marked wrong, even when it loses on the actual deal. The question says it's a guess before you play, and afterwards you see how often each card works.
• How the bidding is read. Where the system's rules cover a call (an opening, a response, opener's rebid), it means what they say. Elsewhere the reading is plain and sparing: an overcall shows a five-card suit and some points, a raise shows support, a takeout double is short in their suits. Point ranges get a point of slack, and any part the real hand contradicts, as a convention or a psych might, is dropped, so the actual deal always fits.
• The words. Claude, Anthropic's AI, writes each lesson's intro, explanations and takeaways, but decides nothing. The right cards, the questions, and the facts of each position (who can still hold which cards, who has shown out, each card's tricks and odds) come first, from the solver and from code, and the AI writes from them. A second AI pass checks the words against the same facts, a code check flags any "can't lose" or "100%" where no card is certain, and an admin can read and correct every lesson. Words can still slip: if you find one, Something wrong or unclear? on the lesson tells us.

Practice

• Deal me a hand. Four hands shuffled at random. The contract is par: what the best bidding by both sides would reach, from the solver's table of every contract. Declarer is the hand that would have bid it first (in a suit the one with more trumps, in notrump the balanced one, then the stronger), and the deal is turned so you declare from South or defend from West. There's no auction: you see the contract only.
• Each card is marked against best play on the actual deal: a ✓ for a right card where at least half the cards were wrong, or the tricks a card cost. Practice doesn't use the odds yet, so at a guess a sound play can show as costing a trick when the cards lie badly for it.
• Opening leads. Each lead is tried on about 20 layouts that keep declarer's and dummy's strength and trump length close to the real hands, each played perfectly. You see how often each lead beats the contract, and its tricks.
• Pick the contract. You see your hand and partner's and name the contract. It's scored with duplicate scoring from the solver's tricks, and compared with par.
• Techniques. Hands dealt to fit a technique, and kept only when the solver's best line uses it.
• The hand of the day. One deal for everyone: from the same archives as the lessons, or dealt by the app and kept only when it has decisions to get right. You declare against the solver's best defense, and your first try counts.
• Mini-bridge. The side with more points declares, from its stronger hand.

The robots

• They play from what a player would see: their own hand, dummy, and the cards played. When a robot has a real choice, it deals the hands it can't see into layouts that fit what it knows (12 of them, 48 from trick 5), solves them, and plays the card that does best over them. So, like a player, it can guess wrong, and the end of the hand says when its guesses gave you a trick.
• They defend as if they'd heard a natural auction. A random deal has none, so robot defenders assume what one would usually show of declarer's and dummy's hands: their strength within 2 points, their trumps within a card, any suit of five cards or more, and whether they're balanced.
• They play their cards as people do: the top of a sequence or fourth best on lead, second hand low, third hand high, attitude signals on partner's lead and count on declarer's. A robot declarer reads robot defenders' signals, never yours.
• How good are they? Against perfect play on a standard set of 320 deals, robot defenders lose about a third of a trick a deal, and a robot declarer a little under half a trick.
• Bid with a robot. Your partner bids SAYC's basics (below), and past them places the contract by the points and fits you've shown. The opponents pass, and the contract you reach is judged against par.

Bidding

• The system's rules. SAYC's basics are written as rules: openings, responses, and opener's rebid, counting high-card points only. They mark your calls in Bid it and in the bidding quizzes. Where they don't cover an auction there's no mark: the rules don't guess.
• The bid of the day. The app proposes each problem and the AI drafts its answer; an admin approves or changes them, scoring each call as expert panels do (100 for the best, less for the others). Where the problem is a contract decision, the solver checks it over layouts that fit the bidding.
• Bidding advice in Review is the AI's, for SAYC or 2/1, whichever you choose.

Your own hands

Paste a hand you played as a PBN, from Trickster Cards or any bridge app that exports one (a Chrome extension brings Trickster Cards hands in with one click), and ask about the bidding, the opening lead or the play, or for a full post-mortem. That analysis is Claude's: it gets the hands, the auction and the play, with each hand's points and shape counted in code, but the solver doesn't check it, so read it as advice, not a ruling. To test a line, open the hand in Play it yourself, where the solver judges every card.

Feedback

Players' feedback shapes the app: the odds at guesses came from players on r/bridge pointing out that a double-dummy solver calls the lucky card right. If something looks wrong, or you'd like to know how something works, send us a message. In the app, Feedback is at the foot of every page.