Human Agent Playground Chess

Piece movement

• King: one square in any direction.
• Queen: any number of squares along ranks, files, or diagonals.
• Rook: any number of squares along ranks or files.
• Bishop: any number of squares along diagonals.
• Knight: an L shape, jumping over pieces.
• Pawn:
  • moves forward one square
  • from its starting rank may move forward two squares if clear
  • captures one square diagonally forward
  • promotes on the last rank

Special rules

Castling

• Castling moves the king two squares toward a rook and places that rook on the square the king crossed.
• It is legal only if:
  • neither the king nor that rook has moved
  • the squares between them are empty
  • the king is not currently in check
  • the king does not cross or land on an attacked square

En passant

• En passant is only available immediately after a pawn advances two squares and lands beside an enemy pawn.
• The enemy pawn may capture it as if it had moved only one square.
• If the capture is not taken on the next move, the right disappears.

Promotion

• A pawn reaching the last rank must promote.
• In this project, move payloads may include a promotion field when needed.
• Usual promotion targets are queen, rook, bishop, or knight.

Game-ending conditions

• Check: the king is under attack.
• Checkmate: the side to move is in check and has no legal move.
• Stalemate: the side to move is not in check but has no legal move.
• Draws may also come from repetition, insufficient material, or other server-supported termination logic.

Notation in this playground

• Legal move and play payloads use coordinate fields such as:
  • { "from": "e2", "to": "e4" }
• Move details may also include SAN such as:
  • Nf3
  • Qxd5
  • O-O
• SAN is useful for summaries, but legality must always come from the server's legal-move tool or API response.

Agent reasoning rules for Chess

• Always base the move on the current live position, not on an opening script alone.
• Prefer legal move data from the server over memory.
• Explain why the move is good now:
  • king safety
  • center control
  • development
  • tactical gain
  • threat prevention
• Do not describe a long forced line unless the current position truly justifies it.
• Do not claim a move is legal without checking the current legal-move source.

Practical reminders

• White moves first.
• If it is not your turn, do not invent a move.
• When the position changes, recompute your plan from the new board state.
• If SAN and coordinate notation seem inconsistent, trust the server state and legal moves first.