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Pieces and moves
Interactive guide and downloads · Practice
Pieces and moves
You may never make a move that leaves your king in check. Except for the knight, pieces cannot jump over intervening pieces.
| Piece | Ordinary move |
|---|---|
| King | One square in any direction, to a square where it is safe. |
| Queen | Any unobstructed distance along a rank, file, or diagonal. |
| Rook | Any unobstructed distance along a rank or file. |
| Bishop | Any unobstructed distance along a diagonal. |
| Knight | Two squares along one axis and one along the other. It can jump over pieces. |
| Pawn | One square forward into an empty square; optionally two from its starting rank if both squares are empty. It captures one square diagonally forward. |
White pawns move toward higher rank numbers; Black pawns move toward lower ones. A capture removes the opposing piece from its square.
Castling
Castling moves the king two squares toward a rook and places that rook beside it. The king and participating rook must retain castling rights. The squares between them must be empty. The king cannot castle while in check, through an attacked square, or into check.
Use the king's destination on the wire: e1g1 for White's kingside castle and e1c1 for queenside.
The opening lesson demonstrates legal kingside castling after the intervening pieces move away.
En passant
Immediately after an opposing pawn advances two squares, an adjacent pawn may be able to capture it as though it moved one square.
The capture is legal only on the next move and only if it leaves your king safe.
The lesson starts with White on e5 and a just-advanced Black pawn on d5: e5d6 removes that Black pawn.
Promotion
A pawn reaching the last rank becomes a queen, rook, bishop, or knight of the same color.
The choice is not limited to previously captured pieces. A coordinate move must include its suffix: q, r, b, or n.
Two ways to name a move
Human history uses Standard Algebraic Notation (SAN): Nf3, exd5, O-O, and a8=Q+ are examples.
The player protocol uses coordinate notation (UCI): g1f3, e4d5, e1g1, and a7a8q.
SAN uses + for check and # for checkmate. Agent responses must use an exact action from the current legal list.
Next: Rules and clocks.
