ok

src/backend/Board.java

@@ -13,10 +13,6 @@ public class Board {
     private ArrayList<int[]> highlightedSquares = new ArrayList<>();
     private ArrayList<Move> moveHistory = new ArrayList<>();
 
-
-    
-    
-
 	public Board(int colNum, int lineNum) {
         this.width = colNum;
         this.height = lineNum;
@@ -250,9 +246,24 @@ public class Board {
 	}
 
 	public Board(Board board) {
-		//TODO
+        this.width = board.width;
+        this.height = board.height;
+        this.turnNumber = board.turnNumber;
+        this.selectedX = board.selectedX;
+        this.selectedY = board.selectedY;
 
-	}
+        this.pieces = new ArrayList<>();
+        for (Piece p : board.pieces) {
+            this.pieces.add(new Piece(p.getType(), p.isWhite(), p.getX(), p.getY()));
+        }
+
+        this.highlightedSquares = new ArrayList<>();
+        for (int[] pos : board.highlightedSquares) {
+            this.highlightedSquares.add(new int[]{pos[0], pos[1]});
+        }
+
+        this.moveHistory = new ArrayList<>(board.moveHistory);
+    }
 	
 	public void playMove(Move move) {
 	    if (move == null) return;
@@ -289,6 +300,31 @@ public class Board {
 	    selectedY = -1;
 	    highlightedSquares.clear();
 	}
+	public boolean isKingInCheck(boolean isWhite) {
+        Piece king = null;
+        for (Piece p : pieces) {
+            if (p.getType() == PieceType.King && p.isWhite() == isWhite) {
+                king = p;
+                break;
+            }
+        }
+        if (king == null) return true;
+
+        int kingX = king.getX();
+        int kingY = king.getY();
+
+        for (Piece p : pieces) {
+            if (p.isWhite() != isWhite) {
+                ArrayList<int[]> moves = Move.getLegalMoves(this, p);
+                for (int[] move : moves) {
+                    if (move[0] == kingX && move[1] == kingY) {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
 
 	
 	public Piece getPieceAt(int x, int y) {

src/backend/Move.java

@@ -107,6 +107,26 @@ public class Move {
         return moves;
     }
 
+    public static ArrayList<int[]> getLegalMoves(Board board, Piece piece) {
+        ArrayList<int[]> legalMoves = new ArrayList<>();
+        ArrayList<int[]> candidateMoves = getPossibleMoves(board, piece);
+
+        for (int[] move : candidateMoves) {
+            Board clone = new Board(board); // Deep copy constructor
+            Piece moved = clone.getPieceAt(piece.getX(), piece.getY());
+
+            // Play the simulated move
+            Piece captured = clone.getPieceAt(move[0], move[1]);
+            Move simulated = new Move(moved, piece.getX(), piece.getY(), move[0], move[1], captured);
+            clone.playMove(simulated);
+
+            if (!clone.isKingInCheck(piece.isWhite())) {
+                legalMoves.add(move);
+            }
+         }
+        return legalMoves;
+    }
+    
     private static boolean isInsideBoard(Board board, int x, int y) {
         return x >= 0 && x < board.getWidth() && y >= 0 && y < board.getHeight();
     }