Right-click bugfix

src/ChessboardMouseAdapter.java

@@ -16,6 +16,7 @@ public class ChessboardMouseAdapter extends MouseAdapter {
      * @param me mouse event
      */
     public void mousePressed(MouseEvent me) {
+        if(me.getButton() != MouseEvent.BUTTON1) return;
         dragging = false;
         lastClicked = System.currentTimeMillis()+250;
     }