anchor.diff:    Widget build(BuildContext context) {
       final ThemeData theme = Theme.of(context);
       final bool isDark = theme.brightness == Brightness.dark;
  +    final MediaQueryData media = MediaQuery.of(context);
  +    final bool centerHome = media.orientation == Orientation.portrait && media.size.height < 800.0;
   
       const Curve switchOutCurve = const Interval(0.4, 1.0, curve: Curves.fastOutSlowIn);
       const Curve switchInCurve = const Interval(0.4, 1.0, curve: Curves.fastOutSlowIn);
  
positive.code:               duration: _kFrontLayerSwitchDuration,
                switchOutCurve: switchOutCurve,
                switchInCurve: switchInCurve,
                child: _category != null
                  ? new _DemosPage(_category)
                  : new _CategoriesPage(
  
negative.code:         child: new LayoutBuilder(
            builder: (BuildContext context, BoxConstraints constraints) {
              final double columnWidth = constraints.biggest.width / columnCount.toDouble();
              final double rowHeight = math.min(225.0, columnWidth * aspectRatio);
              final int rowCount = (categories.length + columnCount - 1) ~/ columnCount;
  
              // This repaint boundary prevents the inner contents of the front layer
  