anchor.diff:          b.darkColor,
           b.textColor,
           b.style,
  +        b.margin * t,
           b._position,
           b._opacity * t.clamp(0.0, 1.0),
  -        b.margin * t,
         );
       }
       if (b == null) {
  
positive.code:         a.darkColor,
          a.textColor,
          a.style,
          a._position,
          a._opacity * (1.0 - t).clamp(0.0, 1.0),
          a.margin * t,
        );
      }
      return new FlutterLogoDecoration._(
  
negative.code:       Color.lerp(a.darkColor, b.darkColor, t),
        Color.lerp(a.textColor, b.textColor, t),
        t < 0.5 ? a.style : b.style,
        EdgeInsets.lerp(a.margin, b.margin, t),
        a._position + (b._position - a._position) * t,
        (a._opacity + (b._opacity - a._opacity) * t).clamp(0.0, 1.0),
      );
    }
  
  