diff --git a/ChessForms/BoardDisplay.cs b/ChessForms/BoardDisplay.cs
index 6e6a95e..8f6964b 100644
--- a/ChessForms/BoardDisplay.cs
+++ b/ChessForms/BoardDisplay.cs
@@ -356,6 +356,11 @@ void DrawDangerzone()
                 continue;
             }
 
+            if (item.Value.Count == 0)
+            {
+                continue;
+            }
+
             ColorSquare(item.Key, DangersquareColor);
         }*/
 
@@ -566,7 +571,7 @@ void CellClicked(object sender, EventArgs e)
             case MouseButtons.None:
                 break;
             case MouseButtons.Right: // Mark square.
-                // do not change color if square is already colored.
+                                     // do not change color if square is already colored.
                 if ((recentMoveFrom?.File == cellX && recentMoveFrom?.Rank == cellY) ||
                     (recentMoveTo?.File == cellX && recentMoveTo?.Rank == cellY))
                 {
diff --git a/ChessGame/Chessboard.cs b/ChessGame/Chessboard.cs
index 9236cdc..4f6bc44 100644
--- a/ChessGame/Chessboard.cs
+++ b/ChessGame/Chessboard.cs
@@ -50,8 +50,12 @@ public Chessboard(Chessboard board)
         MovedPieces = new HashSet<Piece>(board.MovedPieces);
         Moves = new Stack<Move>(board.Moves);
 
-        // not needed before executing move
-        Dangerzone = new Dictionary<Coordinate, List<Piece>>();
+
+        Dangerzone = new Dictionary<Coordinate, HashSet<Piece>>();
+        foreach (var item in board.Dangerzone)
+        {
+            Dangerzone[item.Key] = new HashSet<Piece>(item.Value);
+        }
     }
 
     /// <summary>
@@ -71,8 +75,11 @@ public Chessboard(Chessboard board, Move move)
         MovedPieces = new HashSet<Piece>(board.MovedPieces);
         Moves = new Stack<Move>(board.Moves.Reverse());
 
-        // is refreshed in simulatemove
-        Dangerzone = new Dictionary<Coordinate, List<Piece>>();
+        Dangerzone = new Dictionary<Coordinate, HashSet<Piece>>();
+        foreach (var item in board.Dangerzone)
+        {
+            Dangerzone[item.Key] = new HashSet<Piece>(item.Value);
+        }
 
         SimulateMove(move);
     }
@@ -92,7 +99,7 @@ public Chessboard(byte width, byte height, Gamemode gamemode)
         CurrentState = GameState.NotStarted;
 
         Pieces = new Dictionary<Coordinate, Piece>();
-        Dangerzone = new Dictionary<Coordinate, List<Piece>>();
+        Dangerzone = new Dictionary<Coordinate, HashSet<Piece>>();
         Moves = new Stack<Move>();
         MovedPieces = new HashSet<Piece>();
     }
@@ -105,7 +112,7 @@ public Chessboard(byte width, byte height, Gamemode gamemode)
     /// <summary>
     /// Gets a dictionary that describes intersection squares. An intersection square is a square which one or more pieces threaten at once.
     /// </summary>
-    public Dictionary<Coordinate, List<Piece>> Dangerzone { get; }
+    public Dictionary<Coordinate, HashSet<Piece>> Dangerzone { get; }
 
     /// <summary>
     /// Gets previous moves, that resolve to this position.
@@ -361,7 +368,7 @@ public bool IsKingInCheck(TeamColor color)
         }
 
         // Get list of pieces aiming on the square the king sits on.
-        if (Dangerzone.TryGetValue(position, out List<Piece> pieces))
+        if (Dangerzone.TryGetValue(position, out HashSet<Piece> pieces))
         {
             // Returns true if any of the pieces are of opposite teamColor.
             return pieces.Any(p => p.Color != color);
@@ -528,7 +535,7 @@ public Move GetMoveByNotation(string notation, TeamColor teamColor, MoveNotation
     /// <returns></returns>
     public int IsDangerSquare(Coordinate position, TeamColor teamColor)
     {
-        if (Dangerzone.TryGetValue(position, out List<Piece> pieces))
+        if (Dangerzone.TryGetValue(position, out HashSet<Piece> pieces))
         {
             return pieces is null ? 0 : pieces.Count(p => p.Color == teamColor);
         }
@@ -543,7 +550,7 @@ public int IsDangerSquare(Coordinate position, TeamColor teamColor)
     /// <returns></returns>
     public int GetDangerSquareSum(Coordinate position)
     {
-        if (!Dangerzone.TryGetValue(position, out List<Piece> pieces))
+        if (!Dangerzone.TryGetValue(position, out HashSet<Piece> pieces))
         {
             // No pieces can capture this tile.
             return 0;
@@ -697,7 +704,7 @@ void UpdateDangerzones(Piece piece)
                 // Make new list of pieces aiming on this square if there isn't one already.
                 if (!Dangerzone.ContainsKey(destination))
                 {
-                    Dangerzone[destination] = new List<Piece>();
+                    Dangerzone[destination] = new HashSet<Piece>();
                 }
 
                 // Add this move to dangerzone.
diff --git a/ChessGame/Piece.cs b/ChessGame/Piece.cs
index bead1bc..17c831f 100644
--- a/ChessGame/Piece.cs
+++ b/ChessGame/Piece.cs
@@ -70,6 +70,7 @@ public IEnumerable<Move> GetMoves(Chessboard board, bool guardedSquaresOnly = fa
 
     public override string ToString() => Notation.ToString();
 
+    /*
     public override bool Equals(object obj)
     {
         return obj is Piece piece &&
@@ -85,5 +86,5 @@ public override int GetHashCode()
         hashCode = hashCode * -1521134295 + Color.GetHashCode();
         hashCode = hashCode * -1521134295 + MaterialValue.GetHashCode();
         return hashCode;
-    }
+    }*/
 }