Chess

The fourth of the centre's board games: chess, the game of kings - with a friend, or the computer in the other seat, with a clock or without.

The game

The standard game: each side's king, queen, rooks, bishops, knights and pawns, White moving first; castling, en passant and a pawn promoted to the piece its player chooses.
Checkmate wins. Stalemate, the same position three times, fifty moves each without a capture or a pawn moved, not enough pieces left to mate, or a draw agreed, is a draw.

Two at a table, a person or the computer in each seat; or play alone against the computer whenever you like.
Whoever sets a table up chooses a clock or none - 5 minutes each with 3 seconds a move, 10 with 5, 15 with 10, or 30 - how well the computer plays - gently, steadily or its best - and whether hints are given. White goes to each player in turn, game by game.
The clock is kept by the centre's own time, so it is fair whoever's connection is slower; a flag fallen ends the game at once.
The board is drawn from your side; pick a piece and where it may go is marked; offer a draw, resign, copy the game's moves as PGN. Leader boards rank a room's players, a win a point and a draw half; and the game for visitors to try.

Nothing is hidden in chess, so the computer sees exactly what you see, and no more.

It looks ahead: every move it could make, every reply, and so on, a move deeper each time round, the most promising tried first, and lines that cannot matter cut short - at its best many hundreds of thousands of positions a move.
At the end of each line it plays out the captures until the position is quiet, so it does not stop counting half way through an exchange.
It judges a position by the material left and where each piece stands - knights and bishops towards the middle, rooks on open files and the seventh rank, the king sheltered behind its pawns while the queens are on, and brought out as the board empties - pawns doubled, isolated or passed, and the bishop pair.
Steadily it looks four moves ahead; gently two, with more chance in its judgement. With a clock it takes its share of the time left. Offered a draw, it accepts only when it stands worse.
Ask for a hint and it rings the piece it would move and draws an arrow to where it goes, and says why.

Its thinking runs in your own browser, in WebAssembly.

Back to the centre; how to find your way around, and what it costs (nothing): frequently asked questions.