Update the board file

src/backend/Board.java

@@ -171,19 +171,31 @@ public class Board {
 		      if(selectedX == x && selectedY == y) {
 		            selectedPosition = null;
 		            highlightedPositions.clear(); //Unhighlight
+		            return;
+		        }
+		      //To check if square valid
+		      boolean valid = false;
+		      for (int[] pos : highlightedPositions) {
+		    	  if (pos[0]==x&&pos[1]==y) {
+		    		  valid = true;
+		    		  break;
+		    	  }
 		      }
-		      
 		      // If a piece is selected and the user clicks a new position
-		      else {
+		      if (valid) {
 		    	  movePiece(selectedX, selectedY, x, y);
-		    	  // Update turn
+		    	  //update turn
 		    	  this.turnNumber++;
 			      this.turnWhite=!this.turnWhite; 
+		      }
+		      else {
+		    	  System.out.println("Blocked! This is not a valid move.");
 		    	  
+		      }	
 			      // Deselect the position after moving
 			  this.selectedPosition = null;
 			  highlightedPositions.clear();//Clear after move
-		      }
+		      
 		    } 
 		      
 	 }