Chess

Six levels, and a coach that tells you why

Setting up…

YouWhite · moves first

ComputerBlack

Opponent

Level

You play

Coach Opening

Coach tips as I play Show where a piece can go Mark the last move Turn the board around

Moves

Rules

The board is 8×8 with a light square in each player's right-hand corner. White moves first, and then the players alternate. Each side has a king, a queen, two rooks, two bishops, two knights and eight pawns.
How the pieces move. The rook goes any distance straight, the bishop any distance diagonally, the queen either. The knight jumps two squares one way and one the other, over anything in between. The king moves one square in any direction. Everything but the knight is blocked by the first piece in its path, and takes by landing on an enemy piece.
Pawns are the odd ones. They move one square forward — two from their starting square — but take one square diagonally forward, which is the only move they make that is not the move they take with.
En passant. A pawn that goes two squares and lands beside an enemy pawn may be taken by it as if it had gone only one — but only at once, on the very next move.
Promotion. A pawn that reaches the far rank becomes a queen, rook, bishop or knight of its own colour. It is nearly always a queen; a knight is occasionally better, because a knight does what a queen cannot.
Castling moves the king two squares towards a rook and the rook to the far side of it. It needs the king and that rook to have never moved, no pieces between them, and a king that is not in check, does not pass through an attacked square, and does not land on one.
Check and checkmate. A king that is attacked is in check and must be got out of it — by moving, by blocking, or by taking the attacker. A king in check with no way out is checkmated, and the game is over.
Draws. A player to move with no legal move and no check is stalemated: a draw. So is the same position three times over, fifty moves by each side with no capture and no pawn move, too little material left to mate, or simply agreement.

The pieces

The values are the usual rough ones, and they are what this computer counts with. They are a guide, not a law: a knight in a closed position beats a rook with nothing to do.

Opening strategy

Control the centre. Open with a centre pawn — 1.e4 or 1.d4. A pawn on e4 or d4 takes squares away from their pieces before they are even out, and frees your own bishop and queen in the same move. Every piece you own is worth more in the middle of the board than at the edge, and the opening is the argument over who gets there first.
Develop the minor pieces. Get the knights and bishops off the back rank and onto squares where they do something. A piece still at home on move twelve is a piece you are playing without. Aim each one at the centre: a knight on the rim really does have half the squares of a knight in the middle.
Knights before bishops. A knight has one natural square — f3 and c3 for White, f6 and c6 for Black — and almost nothing to gain by waiting. A bishop has a choice of diagonals, and the choice gets easier once the pawns have settled. So bring the knights out first and let the bishops see what they are choosing between.
Castle early. Inside the first ten moves, get the king behind a wall of pawns and out of the centre, where the files are about to open. Castling does two jobs at once: the king goes somewhere safe and a rook comes towards the middle. Leave it too long and you will find you cannot castle at all.
Delay the queen. The queen is worth nine of anything and can be attacked by all of them. Bring her out early and every knight and bishop that comes out with a threat gains a free move chasing her. Develop the cheap pieces first; the queen has all game to find a square.
The one rule behind the rules: do not move the same piece twice in the opening unless you are made to. Every move spent moving a developed piece again is a move the other player spends developing a new one.

Middlegame strategy

Make a plan. The moves come from the position, not from a list. Look at what is actually in front of you — an open file, a backward pawn, a weak square nobody can defend, a king with no pawns in front of it — and aim at it. A middling plan played consistently beats good moves played at random.
Improve your worst piece. When nothing is forced, find the piece of yours with the fewest squares and the least to do, and give it a better home. This one habit is worth more than any amount of calculation: strong players are the ones with no spare pieces.
Look for tactics — every single turn. Before you play a quiet move, scan the checks, the captures and the threats, yours and theirs. Most games between club players are decided by something that was there to be seen. A loose piece, a pinned defender, two pieces on one diagonal: these are what you are looking for.
Trade when you are ahead. A pawn up with four pieces each is a small edge; a pawn up with nothing but kings and pawns is usually winning. So when you are ahead in material, swap pieces off — queens first, since the queen is the one piece that can turn a lost position round on its own. When you are behind, do exactly the opposite: keep the pieces on and keep it complicated.
Rooks want open files and the seventh rank. A rook on a file with no pawns on it is worth half a piece more than a rook stuck behind its own pawns, and a pair of rooks on the seventh is one of the strongest things in chess.

Endgame strategy

Activate your king. The piece you spent the opening hiding is a fighting piece once the queens come off — roughly as strong as a knight, and it is on the board already. Walk it towards the centre, where it defends its own pawns and gets in front of theirs. A king left on g1 in a pawn endgame is a king that loses the endgame.
Push passed pawns. A passed pawn is one with no enemy pawn in front of it on its own file or either neighbour — nothing stands between it and queening. Push it. Every square it advances makes it harder to stop, and it ties an enemy piece to watching it, which is a piece not defending anything else.
Use your rooks. Put a rook behind a passed pawn — yours or theirs. Behind your own, the rook gains scope with every square the pawn advances; behind theirs, it never has to give ground. A rook in front of a passed pawn is a rook doing nothing but waiting.
Count before you commit. Pawn races are arithmetic, not judgement: count the moves each side needs to queen, remember who is to move, and check whether the new queen gives check on the way. One tempo decides most of them.
Fewer pieces, more precision. Endgames punish carelessness in a way middlegames do not, because there is nothing left to complicate things with. Take the extra ten seconds.

How the computer plays

It plays by the list above. Each of those principles is a term in the computer's judgement of a position, weighted by how far into the game it is — so a castling bonus matters in the opening and fades away once the pieces come off, and the king's walk to the centre is worth nothing in the opening and a great deal at the end. When it plays a move it tells you which of them moved it, because it is reading the same list the coach is.
It looks for mate first, searching checking moves only — the same counting a player does when the attack is on. If there is a forced mate it plays it, and says so.
Then it searches with alpha-beta, iterative deepening, a transposition table, killer and history move ordering, null-move pruning, late move reductions, check extensions and a quiescence search over captures, so it is never fooled by half of an exchange.
The levels are not just slower and faster. A weaker player is not a strong player with less time: they know less and they miss more. So Beginner counts material two moves ahead and knows nothing about pawn structure, king safety or activity — it will take a free piece and hang one the same move. Casual has the opening principles and nothing else. Club plays a real plan. Strong, Expert and Master have the whole list and differ in how deep they look and how often they play something other than their first choice, which at Master is never.
It has an opening book of the main lines — the Ruy Lopez, the Italian, the Sicilian, the French, the Caro-Kann, the Queen's Gambit, the King's Indian — so the first few moves look like chess rather than like a machine feeling its way. Beginner does not use it at all.

Keys

N new game · H hint · U take back · F full-screen board · M sound · Esc clear the selection