Chess

About Chess

Chess is a two-player strategy game played on a board of 64 squares. It grew out of the Indian game chaturanga about 1,500 years ago, travelled through Persia and the Arab world into Europe, and has been played in its modern form since around 1500. It is a favourite in hostels, tea shops and engineering colleges, and it rewards the same careful calculation that engineering asks of you.

This version is written from scratch for Kaamko: the rules, the computer opponent and the piece set are our own. The computer runs in a background worker in your browser, so the page stays responsive while it thinks, and nothing about your games is sent anywhere. Your wins against each level are kept on this device only.

How to play Chess

1. White moves first, then the players alternate. Each side has a king, a queen, two rooks, two bishops, two knights and eight pawns.
2. The king moves one square in any direction. The queen moves any distance in a straight line or diagonal. A rook moves in straight lines, a bishop along diagonals, and a knight jumps in an L shape, two squares one way and one to the side, over any pieces in between.
3. A pawn moves one square forward, or two from its starting square, and captures one square diagonally forward. A pawn that reaches the far rank is promoted; choose the new piece in "Promote to" before you move.
4. You capture by moving onto a square held by an opposing piece. You may never make a move that leaves your own king attacked.
5. Castling: if the king and a rook have not moved, the squares between them are empty, and the king is not in check and does not cross an attacked square, the king moves two squares towards the rook and the rook jumps to the other side of it. To castle here, move the king two squares.
6. En passant: if a pawn moves two squares and lands beside one of your pawns, your pawn may capture it as if it had moved one square, but only on the very next move.
7. Checkmate, where the king is attacked and has no escape, wins. The game is drawn by stalemate, by the same position three times, by fifty moves each with no capture or pawn move, or when neither side has enough pieces left to mate.

To move, tap or click a piece and then its destination; dots show the legal squares. On a keyboard, move between squares with the arrow keys and press Enter to pick up and put down.

Principles for your first hundred games

In the opening, put a pawn in the centre, bring out the knights and bishops before the queen, and castle early to tuck the king away. Do not move the same piece twice without a reason. Before every move, ask what your opponent's last move threatens, and check every capture and every check you could give. Most games between beginners are decided by a piece left undefended, not by deep plans. Count what is attacking a square and what is defending it before you exchange. Once you are ahead in material, trade pieces, not pawns, and the endgame becomes simple.

The four computer levels

The computer uses alpha-beta search with a capture search at the end of each line, and judges positions by material and by where each piece stands. Beginner looks one move ahead and adds noise to its choices, so it blunders. Casual looks two moves ahead, club four, and strong searches as deep as it can in about two seconds. It has no opening book, so its first moves vary, and it is far weaker than a dedicated chess engine. It is a sparring partner, not a grandmaster.