anchor.diff:    }
   }
   
  -class ExposedMineNode extends Component {
  +class ExposedMineNode extends StatelessComponent {
   
     ExposedMineNode({ this.state, this.count });
   
     final CellState state;
     final int count;
   
  -  Widget build() {
  +  Widget build(BuildContext context) {
       StyledText text;
       if (state == CellState.cleared) {
         // Uncovered cell with nearby mine count.
  
positive.code:   );
  }
  
  class CoveredMineNode extends Component {
  
    CoveredMineNode({ this.flagged, this.posX, this.posY });
  
  
negative.code:   final int posX;
    final int posY;
  
    Widget build(BuildContext context) {
      Widget text;
      if (flagged)
        text = buildInnerCell(new StyledText(elements : [textStyles[5], '\u2691']));
  