Chess

Overview

Chess is a two-player strategy board game played on an 8x8 checkered board. Each player controls 16 pieces with the goal of checkmating the opponent’s king.

Status: ✅ Available
Players: 2
Difficulty: Hard
Board: 8x8 checkered board (64 squares)

Objective

Checkmate your opponent’s king by placing it under attack with no legal moves to escape.

Rules

The Board

• 8x8 grid with alternating light and dark squares
• Files (columns) labeled a-h from left to right
• Ranks (rows) labeled 1-8 from bottom to top
• Each player starts with pieces on ranks 1-2 (White) and 7-8 (Black)
• Light square always on the right for each player

The Pieces

Each player starts with:

• 1 King (K): Most important piece
• 1 Queen (Q): Most powerful piece
• 2 Rooks (R): Castle-shaped pieces
• 2 Bishops (B): Diagonal movers
• 2 Knights (N): L-shaped movers
• 8 Pawns (P): Front-line pieces

How Pieces Move

King (K):

• Moves one square in any direction
• Cannot move into check
• Can castle once per game (special move)

Queen (Q):

• Moves any number of squares in any direction (horizontal, vertical, diagonal)
• Most powerful piece
• Cannot jump over pieces

Rook (R):

• Moves any number of squares horizontally or vertically
• Cannot jump over pieces
• Used in castling

Bishop (B):

• Moves any number of squares diagonally
• Cannot jump over pieces
• Each bishop stays on its starting color

Knight (N):

• Moves in an “L” shape: 2 squares in one direction, 1 square perpendicular
• Only piece that can jump over other pieces
• Alternates between light and dark squares

Pawn (P):

• Moves forward one square (or two squares on first move)
• Captures diagonally forward one square
• Promotes to any piece (usually Queen) when reaching the opposite end
• Can capture “en passant” (special pawn capture)

How to Play

Step 1: Setup

• Place board with light square on bottom right
• White pieces on ranks 1-2, Black on ranks 7-8
• Rooks in corners, Knights next to them, Bishops next to Knights
• Queen on her color (White Queen on light square, Black Queen on dark square)
• King on remaining center square
• Pawns on second rank

Step 2: Starting the Game

• White always moves first
• Players alternate turns
• Each turn, move one piece (except castling)

Step 3: Making Moves

• Select a piece and move it according to its movement rules
• Capture opponent’s pieces by moving to their square
• Cannot capture your own pieces
• Cannot move into check
• Must move out of check if in check

Step 4: Special Moves

Castling:

• King and Rook move simultaneously
• King moves 2 squares toward Rook
• Rook moves to square King crossed
• Requirements:
  • Neither piece has moved before
  • No pieces between them
  • King not in check
  • King doesn’t cross or land in check
• Kingside (short) castling: King to g-file
• Queenside (long) castling: King to c-file

En Passant:

• Special pawn capture
• When opponent’s pawn moves 2 squares forward from starting position
• And lands beside your pawn
• You can capture it as if it moved only 1 square
• Must be done immediately on next turn

Pawn Promotion:

• When pawn reaches opposite end (rank 8 for White, rank 1 for Black)
• Must promote to Queen, Rook, Bishop, or Knight
• Usually promote to Queen (most powerful)
• New piece takes effect immediately

Step 5: Check and Checkmate

Check:

• King is under attack
• Must move king, block attack, or capture attacking piece
• Cannot make a move that leaves king in check

Checkmate:

• King is in check
• No legal move can get king out of check
• Game over, attacking player wins

Stalemate:

• Player has no legal moves
• King is NOT in check
• Game ends in a draw

Step 6: Winning the Game

Win by:

• Checkmate
• Opponent resigns
• Opponent runs out of time (in timed games)

Draw by:

• Stalemate
• Mutual agreement
• Threefold repetition (same position 3 times)
• 50-move rule (50 moves without capture or pawn move)
• Insufficient material (e.g., King vs King)

Strategy Tips

Opening Principles

1. Control the center - Place pawns and pieces in center squares (d4, d5, e4, e5)
2. Develop pieces - Move Knights and Bishops out early
3. Castle early - Protect your King
4. Don’t move same piece twice - Develop all pieces
5. Don’t bring Queen out too early - Can be attacked and chased

Middle Game

1. Look for tactics - Forks, pins, skewers, discovered attacks
2. Control key squares - Outposts for Knights, open files for Rooks
3. Coordinate pieces - Work together to attack
4. Pawn structure - Avoid weak pawns, create passed pawns
5. King safety - Keep King protected

End Game

1. Activate King - King becomes strong in endgame
2. Passed pawns - Push pawns toward promotion
3. Rook activity - Rooks on 7th rank are powerful
4. Opposition - King positioning in pawn endgames
5. Calculate precisely - Every move matters

Common Tactics

• Fork: One piece attacks two or more pieces
• Pin: Piece cannot move without exposing more valuable piece
• Skewer: Valuable piece must move, exposing less valuable piece
• Discovered attack: Moving one piece reveals attack from another
• Double attack: Two pieces attack simultaneously
• Sacrifice: Give up material for positional advantage or checkmate

Implementation Details

Current Features

• ✅ 8x8 chess board display
• ✅ All piece movements implemented
• ✅ Turn-based gameplay
• ✅ Check detection
• ✅ Checkmate detection
• ✅ Stalemate detection
• ✅ Castling
• ✅ En passant
• ✅ Pawn promotion
• ✅ Move validation
• ✅ Game state management

Planned Features

• 🔜 AI opponent with difficulty levels
• 🔜 Move history and notation
• 🔜 Undo/Redo moves
• 🔜 Save/Load games
• 🔜 Timer (Blitz, Rapid, Classical)
• 🔜 Hints and analysis
• 🔜 Opening book
• 🔜 Puzzles and tactics trainer
• 🔜 Online multiplayer
• 🔜 Game analysis with engine

Technical Implementation

class ChessGame {
  final List<List<ChessPiece?>> board; // 8x8 grid
  final ChessColor currentTurn;
  final bool whiteKingMoved;
  final bool blackKingMoved;
  final bool whiteKingsideRookMoved;
  final bool whiteQueensideRookMoved;
  final bool blackKingsideRookMoved;
  final bool blackQueensideRookMoved;
  final ChessPosition? enPassantTarget;
  final List<ChessMove> moveHistory;
  final ChessGameStatus status;
}

class ChessPiece {
  final ChessPieceType type;
  final ChessColor color;
}

enum ChessPieceType { king, queen, rook, bishop, knight, pawn }
enum ChessColor { white, black }
enum ChessGameStatus { ongoing, check, checkmate, stalemate, draw }

Algorithms Implemented

1. Move Generation: Calculate all legal moves for each piece
2. Check Detection: Determine if king is under attack
3. Checkmate Detection: Verify no legal moves escape check
4. Stalemate Detection: Verify no legal moves but not in check
5. Castling Validation: Check all castling requirements
6. En Passant Detection: Track pawn double-moves
7. Pawn Promotion: Handle pawn reaching end rank

Chess Notation

Algebraic Notation

• Pieces: K (King), Q (Queen), R (Rook), B (Bishop), N (Knight), Pawn (no letter)
• Files: a-h (columns)
• Ranks: 1-8 (rows)
• Move: Piece + destination square (e.g., Nf3, e4)
• Capture: x (e.g., Bxf7, exd5)
• Check: + (e.g., Qh5+)
• Checkmate: # (e.g., Qh7#)
• Castling kingside: O-O
• Castling queenside: O-O-O
• Promotion: = (e.g., e8=Q)

Example Game

1. e4 e5
2. Nf3 Nc6
3. Bb5 a6
4. Ba4 Nf6
5. O-O Be7
6. Re1 b5
7. Bb3 d6
8. c3 O-O

Glossary

• Check: King is under attack
• Checkmate: King is in check with no escape (game over)
• Stalemate: No legal moves but not in check (draw)
• Castling: Special King and Rook move
• En Passant: Special pawn capture
• Promotion: Pawn reaching opposite end becomes another piece
• Fork: One piece attacks multiple pieces
• Pin: Piece cannot move without exposing valuable piece
• Skewer: Valuable piece must move, exposing another
• Discovered attack: Moving reveals attack from another piece
• Sacrifice: Giving up material for advantage
• Gambit: Sacrificing material in opening for position
• Endgame: Final phase with few pieces remaining
• Opening: First phase of the game
• Middle game: Main phase between opening and endgame

References

• Chess Rules - Wikipedia
• Chess.com Learn
• Lichess Practice
• FIDE Laws of Chess