anchor.diff:          css.rule('&.z5 > .Paper_shadow', [
             paperShadow(5)
           ])
  +      ]),
  +
  +      css.rule('.Paper_shadow', [
  +        css.position('absolute'),
  +        css.top(0),
  +        css.right(0),
  +        css.bottom(0),
  +        css.left(0),
  +        css.borderRadius('inherit'),
  +        css.transition('box-shadow 0.5s $swiftEaseInOut'),
         ])
       ];
   }
  
positive.code: 
  class PaperStyleSheet extends css.StyleSheet {
    build() => [
        css.rule('.Paper_shadow', [
          css.position('absolute'),
          css.top(0),
          css.left(0),
          css.right(0),
          css.bottom(0),
          css.borderRadius('inherit'),
          css.transition('box-shadow 0.5s $swiftEaseInOut'),
        ]),
  
        css.rule('.Paper', [
          css.rule('&.round', [
            css.borderRadius('3px')
          ]),
          css.rule('&.circle', [
            css.borderRadius('50%')
          ]),
  
negative.code:       ..classes.add('Paper');
  
      shadowElement.classes.add('Paper_shadow');
  
      element
        ..append(shadowElement);
    }
  
    v.VRootDecorator<html.DivElement> build() =>
  