anchor.diff:  
     @override
     Widget build(BuildContext context) {
  +    ThemeData theme = Theme.of(context);
  +    ThemeData darkTheme = new ThemeData(
  +      brightness: Brightness.dark,
  +      accentColor: theme.accentColor,
  +      accentColorBrightness: theme.accentColorBrightness,
  +    );
       return new Positioned.fill(
         child: new IgnorePointer(
           child: new CustomSingleChildLayout(
  
positive.code: import 'package:flutter/gestures.dart';
  import 'package:flutter/widgets.dart';
  
  import 'colors.dart';
  import 'typography.dart';
  
  const double _kScreenEdgeMargin = 10.0;
  const Duration _kFadeDuration = const Duration(milliseconds: 200);
  
negative.code:               opacity: 0.9,
                child: new Container(
                  decoration: new BoxDecoration(
                    backgroundColor: darkTheme.backgroundColor,
                    borderRadius: new BorderRadius.circular(2.0)
                  ),
                  height: height,
                  padding: padding,
                  child: new Center(
                    widthFactor: 1.0,
                    child: new Text(message, style: darkTheme.textTheme.body1)
                  )
                )
              )
  