anchor.diff:  
   enum CellState { covered, exploded, cleared, flagged, shown }
   
  -class MineDiggerApp extends App {
  +class MineDigger extends StatefulComponent {
  +  MineDiggerState createState() => new MineDiggerState();
  +}
  +
  +class MineDiggerState extends State<MineDigger> {
     static const int rows = 9;
     static const int cols = 9;
     static const int totalMineCount = 11;
  
positive.code:   // |uiState| keeps track of the visible player progess.
    List<List<CellState>> uiState;
  
    void initState() {
      resetGame();
    }
  
  
negative.code:   final int posX;
    final int posY;
  
    Widget build(BuildContext context) {
      Widget text;
      if (flagged)
        text = buildInnerCell(new StyledText(elements : [textStyles[5], '\u2691']));
  