Frequently Asked Questions

One place for bridge, card games, puzzles, word games, mahjong, noughts and crosses, draughts, backgammon, chess played in your browser, with other people from anywhere or against the computer. The games are played in clubs - game rooms - each run by its own administrators.

Not to try it. As a visitor (Visitor in the bar of the welcome page) you try the games the centre offers visitors, against the computer, with nothing to sign up for. To play with others, join clubs and keep your results, register for an account: one account is for every game and every club. A family may share one email address: each of you registers with your own login name and your own full name.

Only if you ask for it: tick "Send me the centre's occasional news" on your account page, under Email from the centre, or as you register. It is off unless you tick it, it goes only to a confirmed address, and every news email has a link at its foot to stop them.

When you register, the centre sends a link to the address you gave. Opening it confirms the address, and makes you a member: then you may join clubs, and in each you join you are a subscriber, let into its rooms unless a room has a password or its manager keeps subscribers out. Until you do, you may look round the lobby and try the games offered to visitors, as a visitor does. A link works for an hour; if yours has run out, or never came, send another from your account page or the note at the top of every page. A registration not confirmed within 12 hours is removed, and you may register again.

A web browser - on a computer, a tablet or a phone - and nothing else: there is nothing to download or install. The tables work best with the screen turned so that it is wider than it is tall.

In four steps, each inside the one before:

• The lobby - the centre's front room. It lists the game rooms, and has the centre's news and, once it is open, the centre's discussion board.
• Game rooms - the clubs, each for one game. You join one as a guest from the lobby; its administrators can make you a member.
• Rooms - a game room may have rooms of its own, for a session, a group or a level, each with its tables.
• Tables - where the games are played. A game room's or a room's page lists its tables.

• Lobby takes you back to the lobby from anywhere.
• The link at the far left goes back up a step - from a table to its room, from a room to its game room.
• Your name opens your own menu: your account, your comments and suggestions to the centre, and - for the centre's administrator - Administration. A badge on it means something new is waiting for you.
• On a small screen the bar keeps to one row: its buttons show their pictures alone - hold a finger on one, or point at it, for its name - and those in the middle slide along when even their pictures do not fit, an arrow at either end showing that more are that way.
• Moderation appears only for moderators, when something is waiting for them.
• Sign out ends your session on this device.

Go into a game room from the lobby (join it first if you have not), or into one of its rooms. Its page lists the tables: sit at one with a free seat, or start your own and choose its options. The computer plays any seat nobody is sitting in.

Messages from the centre or from your clubs. One you have not read appears as soon as you arrive on any page; I have read it puts it away.

The centre and every club have a blog - their news, written by those who run them. The lobby and each game room may also have a discussion board, once its moderators have opened it, where members start topics and reply to each other. Each is reached from the buttons at the top of the lobby or the game room's page; a number on the board's button is how many topics have posts you have not read.

Yes. Start a table and leave the other seats empty: the computer plays them. At bridge, a practice table is yours alone, with the computer as partner and opponents, and the other hands shown when you want them. Visitors play the games offered to them on their own too.

Start a table and tell them its name; give it a password if you want it kept to them. They sit down in a free seat, and you can talk to each other at the table.

It bids SAYC, ACOL, 2/1 Game Forcing, Precision Club or Polish Club, and it decides by perfect-information Monte Carlo with policy-consistent sampling.

In plain words: it cannot see the other hands, so it works out what they could be by asking its own bidding rules which hands would have made the calls it has seen. It deals the unseen cards at random many times over - and where the bidding leaves few deals that fit, a swap chain walks from one that fits to the next, swapping cards between the hidden hands - keeping only the deals that agree with what every call showed and every card played so far, and solves each one double dummy - as if all four hands were face up - with an exact double dummy solver. Only those imagined deals are solved, never the real one at the table: the computer sees no more of the cards than its own seat may. It then chooses the call or card that does best across them.

In a contested auction it bids each choice it is weighing - pass, double, or bid on - out to the end on every deal, and scores the contract each reaches; in the play it looks ahead the same way, card by card. Ask the table for help, and it says what it would play and why. There is more on the bridge page.

The computer's words can be held to the everyday or the common when a table is started (The bots' words), or in Settings when you play alone: about the 10,000 or the 30,000 words English uses most, with their plurals and other forms, and the short words a medium-sized dictionary has. You may still play any word of the list yourself. Whatever its words, the computer never plays a slur, or swearing, or a word whose usual meaning is vulgar or offensive.

Press Meanings, under the bar, or open the Words tab behind the gear: every word on the board is there, the last play's first, and a word tapped shows what it means - the computer's words and everybody else's too. A word like cats shows the meanings of cat.

The meanings are from Open English WordNet, under the Creative Commons Attribution 4.0 licence, and from Wiktionary, by its contributors, under Creative Commons Attribution-ShareAlike 4.0 (as kaikki.org extracts it). The centre's collection of them is offered under the same ShareAlike licence: ask through Comments and suggestions. Each definition has been through the centre's moderation, as anything written here is, and a few are shown only once a person has read them; a word without a meaning says so.

Yes. Each deal is made by taking the layout apart a free pair at a time and giving each pair matching tiles, so there is always a way to clear it - though a careless pair can bury the tile you need: take a move back, or Shuffle when no pair is left. The computer's hint sees only the tiles in view: it deals the hidden ones out a dozen ways that fit, solves each, and suggests the pair that clears the board in the most. More on the mahjong page.

At the classic game, at its best, it never loses: it searches every game to its end. At Ultimate it plays thousands of games out at random from each move and chooses the one that does best (Monte Carlo tree search); at five in a row it weighs every square by the rows of five it would make or stop. Each table chooses how well it plays - gently, steadily or its best. More on the noughts and crosses page.

It looks ahead: every move it could make, every reply, and so on - eight moves deep in English draughts at its best, six in international - following any captures to their end, and judges each position it reaches by the pieces left, kings worth more than men and men worth more the further on they are. Gently and steadily it looks less far, and adds a little chance. More on the draughts page.

Yes. Each table's dice come from its own random seed, drawn in turn as they are rolled, the same for everybody at the table - so nobody, the computer included, can see or choose the next roll, and a game the centre restarts comes out exactly as it was. The computer's play looks only at the board and the dice rolled. More on the backgammon page.

At its best, a good club player: it looks ahead move by move - every move, every reply, deeper and deeper, many thousands of positions a move - and follows the captures to their end, judging each position by the pieces left and where they stand. Steadily it looks four moves ahead; gently two, with more chance. With a clock its thinking takes its share of the time left. More on the chess page.

Under your name, top right: Your account. A password needs 10 to 30 characters, with a capital letter, a digit and a symbol, and no spaces.

The centre's administrator can give you a temporary one, which you change as soon as you sign in. Ask through your club, or a member you know.

After five wrong passwords your account is held back from that device for five minutes; after ten failed sign-ins from one place, that place is held back for half an hour. Anywhere else, you sign in as usual - nobody can lock you out by guessing at your name.

Yes: everything written in the centre - posts, notices, chat, names - is read as it is written. A sentence that would clearly offend is taken out, with a mark where it was; something that might offend, or that swears however mildly, waits for a moderator before anybody else sees it. Chat at a table that might offend is simply not sent.

Each post on a blog or a board has Report it: say why if you want to, and its moderators look at it.

The centre is free to use at present: no subscription, no charges, and no adverts. Nor does it carry anybody else's tracking or advertising code - its pages load nothing from anywhere but the centre itself.

Under your name, top right: Comments and suggestions. Those who run the centre read them, and their answers come back to you there.

Yes, and with thanks to those who made it:

• DDS 3.1, a double dummy solver - which the bridge computer players use only on the deals they imagine, never on the real hands at a table - Copyright © 2006-2014 by Bo Haglund, 2014-2018 by Bo Haglund and Søren Hein; version 3 maintained by Martin Nygren and contributors. github.com/dds-bridge/dds, under the Apache License 2.0. The bridge computer players are also measured and tuned against a million practice deals solved by it in advance, away from any table.
• SVG-cards by David Bellot - the Traditional card faces - under the GNU Lesser General Public License 2.1; and SVG playing cards by Adrian Kennard (RevK) - the Clear faces - in the public domain.
• SCOWL, the word list by Kevin Atkinson, for Wordgrid's British words; and ENABLE, a word list in the public domain, for its American ones. What the words mean is from Open English WordNet (CC BY 4.0) and Wiktionary (CC BY-SA 4.0), as above, read with SQLite. Which words are everyday or common, for bots held to them, is from wordfreq by Robyn Speer (its data under CC BY-SA 4.0) and SCOWL at its medium size.
• The chess openings - their names, ECO codes and moves - are from Lichess's chess-openings, in the public domain (CC0 1.0). What each opening is for, as the hints say it, is in our own words.
• Resend (resend.com) sends the centre's email - the link that confirms an address, and what waits for those who run the centre - and so holds the addresses it sends to, for that alone.
• toxic-bert by Unitary AI, under the Apache License 2.0, which reads what is written for moderation, run by Microsoft's ONNX Runtime.
• And the centre is built on Microsoft's .NET and ASP.NET Core (with its SignalR connection for the tables), the PostgreSQL database with Npgsql, HtmlSanitizer and AngleSharp, and the Caddy web server - each under its own open source licence.