diff --git a/api/move.go b/api/move.go
index 14db174..be4b447 100644
--- a/api/move.go
+++ b/api/move.go
@@ -18,6 +18,7 @@ const (
 	MoveMessage        MessageType = "move"
 	InvalidMoveMessage MessageType = "invalidMove"
 	ColorDetermined    MessageType = "colorDetermined"
+	TakenEnPassant     MessageType = "takenEnPassant"
 )
 
 func (m WebsocketMessage) IsValidMoveMessage() bool {
diff --git a/chess/bishop.go b/chess/bishop.go
index c0fbab5..30d9dde 100644
--- a/chess/bishop.go
+++ b/chess/bishop.go
@@ -19,3 +19,5 @@ func (b Bishop) GetColor() types.ChessColor {
 func (b Bishop) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	return board.GetNonBlockedDiagonals(fromSquare)
 }
+
+func (b Bishop) AfterMoveAction(board *Board, fromSquare types.Coordinate) {}
diff --git a/chess/board.go b/chess/board.go
index e3fb693..0695c34 100644
--- a/chess/board.go
+++ b/chess/board.go
@@ -13,6 +13,7 @@ type Board struct {
 	position    Position
 	history     []types.Move
 	colorToMove types.ChessColor
+	state       types.AdditionalState
 }
 
 func newBoard() Board {
@@ -20,6 +21,7 @@ func newBoard() Board {
 		position:    make(Position),
 		history:     make([]types.Move, 0),
 		colorToMove: types.White,
+		state:       types.AdditionalState{},
 	}
 }
 
@@ -122,6 +124,9 @@ func (b *Board) CheckAndPlay(move types.Move) (bool, string) {
 	b.history = tempBoard.history
 	b.colorToMove = b.colorToMove.Opposite()
 	b.appendMoveToHistory(move)
+
+	pieceAtStartSquare.AfterMoveAction(b, move.StartSquare)
+
 	return true, ""
 }
 
@@ -184,6 +189,7 @@ func (b Board) getCopyOfBoard() Board {
 		position:    b.position.getCopyOfPosition(),
 		history:     b.history,
 		colorToMove: b.colorToMove,
+		state:       b.state,
 	}
 }
 
@@ -206,6 +212,8 @@ func (b *Board) handleSpecialMove(move types.Move) bool {
 		if !was {
 			was = piece.HandleEnPassant(b, move, b.getLastMove())
 		}
+	case King:
+		was = piece.HandleCastling(b, move)
 	}
 	return was
 }
diff --git a/chess/board_test.go b/chess/board_test.go
index a993983..663c927 100644
--- a/chess/board_test.go
+++ b/chess/board_test.go
@@ -210,3 +210,167 @@ func Test_CheckMove_HistoryWorks(t *testing.T) {
 	}
 	assert.Equal(t, expectedHistory, board.history)
 }
+
+func Test_Promotion_BlackKing(t *testing.T) {
+	t.Run("valid promotion to the right", func(t *testing.T) {
+		var board = newBoard()
+		board.position[types.Coordinate{Col: 5, Row: 1}] = King{Color: types.White}
+
+		board.position[types.Coordinate{Col: 5, Row: 8}] = King{Color: types.Black}
+		board.position[types.Coordinate{Col: 1, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 8, Row: 8}] = Rook{Color: types.Black}
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 1}, EndSquare: types.Coordinate{Col: 5, Row: 2}})
+
+		move := types.Move{
+			StartSquare: types.Coordinate{Col: 5, Row: 8},
+			EndSquare:   types.Coordinate{Col: 7, Row: 8},
+		}
+		good, reason := board.CheckAndPlay(move)
+		assert.True(t, good)
+		assert.Empty(t, reason)
+
+		assert.Equal(t, King{Color: types.Black}, board.position[types.Coordinate{Col: 7, Row: 8}])
+		assert.Equal(t, Rook{Color: types.Black}, board.position[types.Coordinate{Col: 6, Row: 8}])
+		assert.Empty(t, board.position[types.Coordinate{Col: 5, Row: 8}])
+		assert.Empty(t, board.position[types.Coordinate{Col: 8, Row: 8}])
+	})
+
+	t.Run("valid promotion to the left", func(t *testing.T) {
+		var board = newBoard()
+		board.position[types.Coordinate{Col: 5, Row: 1}] = King{Color: types.White}
+
+		board.position[types.Coordinate{Col: 5, Row: 8}] = King{Color: types.Black}
+		board.position[types.Coordinate{Col: 1, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 8, Row: 8}] = Rook{Color: types.Black}
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 1}, EndSquare: types.Coordinate{Col: 5, Row: 2}})
+
+		move := types.Move{
+			StartSquare: types.Coordinate{Col: 5, Row: 8},
+			EndSquare:   types.Coordinate{Col: 3, Row: 8},
+		}
+		good, reason := board.CheckAndPlay(move)
+		assert.True(t, good)
+		assert.Empty(t, reason)
+
+		assert.Equal(t, King{Color: types.Black}, board.position[types.Coordinate{Col: 3, Row: 8}])
+		assert.Equal(t, Rook{Color: types.Black}, board.position[types.Coordinate{Col: 4, Row: 8}])
+		assert.Empty(t, board.position[types.Coordinate{Col: 1, Row: 8}])
+		assert.Empty(t, board.position[types.Coordinate{Col: 2, Row: 8}])
+		assert.Empty(t, board.position[types.Coordinate{Col: 5, Row: 8}])
+	})
+
+	t.Run("king moved already", func(t *testing.T) {
+		var board = newBoard()
+		board.position[types.Coordinate{Col: 5, Row: 1}] = King{Color: types.White}
+
+		board.position[types.Coordinate{Col: 5, Row: 8}] = King{Color: types.Black}
+		board.position[types.Coordinate{Col: 1, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 8, Row: 8}] = Rook{Color: types.Black}
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 1}, EndSquare: types.Coordinate{Col: 5, Row: 2}})
+
+		//Move black
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 8}, EndSquare: types.Coordinate{Col: 4, Row: 8}})
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 2}, EndSquare: types.Coordinate{Col: 5, Row: 1}})
+
+		//Move black back
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 4, Row: 8}, EndSquare: types.Coordinate{Col: 5, Row: 8}})
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 1}, EndSquare: types.Coordinate{Col: 5, Row: 2}})
+
+		move := types.Move{
+			StartSquare: types.Coordinate{Col: 5, Row: 8},
+			EndSquare:   types.Coordinate{Col: 3, Row: 8},
+		}
+		good, _ := board.CheckAndPlay(move)
+		assert.False(t, good)
+	})
+
+	t.Run("promotion right with piece in between", func(t *testing.T) {
+		var board = newBoard()
+		board.position[types.Coordinate{Col: 5, Row: 1}] = King{Color: types.White}
+
+		board.position[types.Coordinate{Col: 5, Row: 8}] = King{Color: types.Black}
+		board.position[types.Coordinate{Col: 1, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 8, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 7, Row: 8}] = Bishop{Color: types.Black}
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 1}, EndSquare: types.Coordinate{Col: 5, Row: 2}})
+
+		move := types.Move{
+			StartSquare: types.Coordinate{Col: 5, Row: 8},
+			EndSquare:   types.Coordinate{Col: 7, Row: 8},
+		}
+		good, _ := board.CheckAndPlay(move)
+		assert.False(t, good)
+	})
+
+	t.Run("promotion left with piece next to king", func(t *testing.T) {
+		var board = newBoard()
+		board.position[types.Coordinate{Col: 5, Row: 1}] = King{Color: types.White}
+
+		board.position[types.Coordinate{Col: 5, Row: 8}] = King{Color: types.Black}
+		board.position[types.Coordinate{Col: 1, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 8, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 4, Row: 8}] = Bishop{Color: types.Black}
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 1}, EndSquare: types.Coordinate{Col: 5, Row: 2}})
+
+		move := types.Move{
+			StartSquare: types.Coordinate{Col: 5, Row: 8},
+			EndSquare:   types.Coordinate{Col: 3, Row: 8},
+		}
+		good, _ := board.CheckAndPlay(move)
+		assert.False(t, good)
+	})
+
+	t.Run("promotion left with piece on castling square", func(t *testing.T) {
+		var board = newBoard()
+		board.position[types.Coordinate{Col: 5, Row: 1}] = King{Color: types.White}
+
+		board.position[types.Coordinate{Col: 5, Row: 8}] = King{Color: types.Black}
+		board.position[types.Coordinate{Col: 1, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 8, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 3, Row: 8}] = Bishop{Color: types.Black}
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 1}, EndSquare: types.Coordinate{Col: 5, Row: 2}})
+
+		move := types.Move{
+			StartSquare: types.Coordinate{Col: 5, Row: 8},
+			EndSquare:   types.Coordinate{Col: 3, Row: 8},
+		}
+		good, _ := board.CheckAndPlay(move)
+		assert.False(t, good)
+	})
+
+	t.Run("promotion left with piece next to rook", func(t *testing.T) {
+		var board = newBoard()
+		board.position[types.Coordinate{Col: 5, Row: 1}] = King{Color: types.White}
+
+		board.position[types.Coordinate{Col: 5, Row: 8}] = King{Color: types.Black}
+		board.position[types.Coordinate{Col: 1, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 8, Row: 8}] = Rook{Color: types.Black}
+		board.position[types.Coordinate{Col: 2, Row: 8}] = Bishop{Color: types.Black}
+
+		//Make dummy move for white
+		board.CheckAndPlay(types.Move{StartSquare: types.Coordinate{Col: 5, Row: 1}, EndSquare: types.Coordinate{Col: 5, Row: 2}})
+
+		move := types.Move{
+			StartSquare: types.Coordinate{Col: 5, Row: 8},
+			EndSquare:   types.Coordinate{Col: 3, Row: 8},
+		}
+		good, _ := board.CheckAndPlay(move)
+		assert.False(t, good)
+	})
+}
diff --git a/chess/king.go b/chess/king.go
index fed3f7f..2891db2 100644
--- a/chess/king.go
+++ b/chess/king.go
@@ -17,5 +17,114 @@ func (k King) GetColor() types.ChessColor {
 }
 
 func (k King) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
-    return board.GetNonBlockedKingMoves(fromSquare)
+	return board.GetNonBlockedKingMoves(fromSquare)
+}
+
+func (k King) AfterMoveAction(board *Board, fromSquare types.Coordinate) {
+	switch k.Color {
+	case types.Black:
+		board.state.BlackKingMoved = true
+	case types.White:
+		board.state.WhiteKingMoved = true
+	}
+}
+
+func (k King) HandleCastling(board *Board, move types.Move) bool {
+	if k.hadMovedBefore(board) {
+		return false
+	}
+
+	valid, dir := k.movedOnValidCastlingSquare(board, move)
+	if !valid {
+		return false
+	}
+
+	switch k.Color {
+	case types.White:
+		board.state.WhiteKingMoved = true
+	case types.Black:
+		board.state.BlackKingMoved = true
+	}
+
+	k.playCastlingOnBoard(board, move, dir)
+	return true
+}
+
+func (k King) hadMovedBefore(b *Board) bool {
+	var hasMoved bool
+	switch k.Color {
+	case types.White:
+		hasMoved = b.state.WhiteKingMoved
+	case types.Black:
+		hasMoved = b.state.BlackKingMoved
+	}
+	return hasMoved
+}
+
+type CastlingDirection string
+
+const (
+	CastlingRight CastlingDirection = "right"
+	CastlingLeft  CastlingDirection = "left"
+)
+
+func (k King) movedOnValidCastlingSquare(b *Board, move types.Move) (bool, CastlingDirection) {
+	var valid bool = false
+
+	switch k.Color {
+	case types.White:
+		castlingSquareRight := types.Coordinate{Col: 7, Row: 1}
+		castlingSquareLeft := types.Coordinate{Col: 3, Row: 1}
+
+		if move.EndSquare == castlingSquareRight &&
+			b.getPieceAt(castlingSquareRight) == nil &&
+			b.getPieceAt(*castlingSquareRight.Left(1)) == nil &&
+			!b.state.WhiteHRookMoved {
+			return true, CastlingRight
+		}
+
+		if move.EndSquare == castlingSquareLeft &&
+			b.getPieceAt(castlingSquareLeft) == nil &&
+			b.getPieceAt(*castlingSquareLeft.Right(1)) == nil &&
+			b.getPieceAt(*castlingSquareLeft.Left(1)) == nil &&
+			!b.state.WhiteARookMoved {
+			return true, CastlingLeft
+		}
+	case types.Black:
+		castlingSquareRight := types.Coordinate{Col: 7, Row: 8}
+		castlingSquareLeft := types.Coordinate{Col: 3, Row: 8}
+
+		if move.EndSquare == castlingSquareRight &&
+			b.getPieceAt(castlingSquareRight) == nil &&
+			b.getPieceAt(*castlingSquareRight.Left(1)) == nil &&
+			!b.state.BlackHRookMoved {
+			return true, CastlingRight
+		}
+
+		if move.EndSquare == castlingSquareLeft &&
+			b.getPieceAt(castlingSquareLeft) == nil &&
+			b.getPieceAt(*castlingSquareLeft.Right(1)) == nil &&
+			b.getPieceAt(*castlingSquareLeft.Left(1)) == nil &&
+			!b.state.BlackARookMoved {
+			return true, CastlingLeft
+		}
+	}
+	return valid, CastlingRight
+}
+
+func (k King) playCastlingOnBoard(board *Board, move types.Move, dir CastlingDirection) {
+	onRow := move.StartSquare.Row
+
+	switch dir {
+	case CastlingRight:
+		delete(board.position, types.Coordinate{Col: 8, Row: onRow})
+		delete(board.position, types.Coordinate{Col: 5, Row: onRow})
+		board.position[types.Coordinate{Col: 7, Row: onRow}] = King{Color: k.Color}
+		board.position[types.Coordinate{Col: 6, Row: onRow}] = Rook{Color: k.Color}
+	case CastlingLeft:
+		delete(board.position, types.Coordinate{Col: 1, Row: onRow})
+		delete(board.position, types.Coordinate{Col: 5, Row: onRow})
+		board.position[types.Coordinate{Col: 3, Row: onRow}] = King{Color: k.Color}
+		board.position[types.Coordinate{Col: 4, Row: onRow}] = Rook{Color: k.Color}
+	}
 }
diff --git a/chess/knight.go b/chess/knight.go
index a8b4f7e..4f31174 100644
--- a/chess/knight.go
+++ b/chess/knight.go
@@ -8,14 +8,16 @@ type Knight struct {
 	Color types.ChessColor
 }
 
-func (k Knight) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
-	return k.GetAllNonBlockedMoves(board, fromSquare)
+func (n Knight) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
+	return n.GetAllNonBlockedMoves(board, fromSquare)
 }
 
-func (k Knight) GetColor() types.ChessColor {
-	return k.Color
+func (n Knight) GetColor() types.ChessColor {
+	return n.Color
 }
 
-func (k Knight) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
+func (n Knight) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	return board.GetNonBlockedKnightMoves(fromSquare)
 }
+
+func (n Knight) AfterMoveAction(board *Board, fromSquare types.Coordinate) {}
diff --git a/chess/pawn.go b/chess/pawn.go
index ceb8f94..916363f 100644
--- a/chess/pawn.go
+++ b/chess/pawn.go
@@ -187,3 +187,5 @@ func (p Pawn) filterBlockedSquares(board Board, fromSquare types.Coordinate, squ
 	}
 	return lo.Intersect(nonBlockedSquares, squaresToBeFiltered)
 }
+
+func (p Pawn) AfterMoveAction(board *Board, fromSquare types.Coordinate) {}
diff --git a/chess/piece_interface.go b/chess/piece_interface.go
index b3aa093..a79d6f5 100644
--- a/chess/piece_interface.go
+++ b/chess/piece_interface.go
@@ -8,6 +8,7 @@ type Piece interface {
 	GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate
 	GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate
 	GetColor() types.ChessColor
+    AfterMoveAction(board *Board, fromSquare types.Coordinate)
 }
 
 func GetPieceForShortName(name types.PieceShortName, color types.ChessColor) Piece {
diff --git a/chess/queen.go b/chess/queen.go
index 5fc8c4f..5b31d75 100644
--- a/chess/queen.go
+++ b/chess/queen.go
@@ -21,3 +21,5 @@ func (q Queen) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) [
     squares = append(squares, board.GetNonBlockedDiagonals(fromSquare)...)
     return squares
 }
+
+func (q Queen) AfterMoveAction(board *Board, fromSquare types.Coordinate) {}
diff --git a/chess/rook.go b/chess/rook.go
index 5f4ee42..59bde33 100644
--- a/chess/rook.go
+++ b/chess/rook.go
@@ -12,9 +12,6 @@ func (r Rook) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []
 	return r.GetAllNonBlockedMoves(board, fromSquare)
 }
 
-func (r Rook) AfterMoveAction() {
-}
-
 func (r Rook) GetColor() types.ChessColor {
 	return r.Color
 }
@@ -22,3 +19,22 @@ func (r Rook) GetColor() types.ChessColor {
 func (r Rook) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	return board.GetNonBlockedRowAndColumn(fromSquare)
 }
+
+func (r Rook) AfterMoveAction(board *Board, fromSquare types.Coordinate) {
+	switch r.Color {
+	case types.Black:
+        if fromSquare.Col == types.RangeLastValid {
+            board.state.BlackHRookMoved = true
+        }
+        if fromSquare.Col == types.RangeFirstValid {
+            board.state.BlackARookMoved = true
+        }
+	case types.White:
+        if fromSquare.Col == types.RangeLastValid {
+            board.state.WhiteHRookMoved = true
+        }
+        if fromSquare.Col == types.RangeFirstValid {
+            board.state.WhiteARookMoved = true
+        }
+	}
+}
diff --git a/types/common.go b/types/common.go
index e0b2145..f7c7f2c 100644
--- a/types/common.go
+++ b/types/common.go
@@ -1,7 +1,5 @@
 package types
 
-
-
 type ChessColor string
 
 const (
@@ -16,3 +14,12 @@ func (c ChessColor) Opposite() ChessColor {
 		return White
 	}
 }
+
+type AdditionalState struct {
+	BlackKingMoved  bool
+	WhiteKingMoved  bool
+	BlackHRookMoved bool
+	BlackARookMoved bool
+	WhiteHRookMoved bool
+	WhiteARookMoved bool
+}
diff --git a/utils/passphrase.go b/utils/passphrase.go
index 272a084..c2bd83c 100644
--- a/utils/passphrase.go
+++ b/utils/passphrase.go
@@ -13,7 +13,7 @@ func NewPassphrase() Passphrase {
 	var retries int
 	var word string
 	var words int = 2
-//TODO make sure passphrases are unique
+	//TODO make sure passphrases are unique
 	for words > 0 {
 		retries = 20
 		for {
@@ -54,6 +54,8 @@ func isProfanity(s string) bool {
 	contains := []string{
 		"nigg",
 		"fag",
+		"ass",
+		"bitch",
 	}
 	startsWith := []string{
 		"spic",