Patterns

ChessGrammar detects 10 tactical patterns, each confirmed by calculating actual material gain through best play.

Fork

A piece attacks two or more enemy pieces simultaneously. The opponent can only save one, resulting in material gain.

• Key square: The square where the forking piece lands
• Targets: The attacked pieces (2+)

Pin

A piece is immobilized because moving it would expose a more valuable piece behind it to attack.

• Key square: The pinning piece's position
• Targets: The pinned piece and the piece behind it

Skewer

A high-value piece is attacked, and when it moves away, a piece behind it is captured.

• Key square: The attacking piece's position
• Targets: The front piece (forced to move) and the piece behind

Discovered Attack

A piece moves, revealing an attack from another piece behind it.

• Key square: The piece that moves (blocker)
• Targets: The piece attacked by the revealed attacker

Double Check

Two pieces give check simultaneously. The king must move (cannot block or capture).

• Key square: Both checking pieces
• Targets: The enemy king

Back Rank Mate

Checkmate delivered on the back rank (1st or 8th), where the king is trapped by its own pawns.

Smothered Mate

Checkmate by a knight where the king is surrounded by its own pieces and cannot escape.

Deflection

A piece is forced away from a critical defensive duty, allowing a tactical blow.

Interference

A piece is placed on a critical square to block a defensive line or communication between enemy pieces.

Trapped Piece

A piece has no safe squares to move to and will be captured.