Sass Susy 2：如何删除；最后一句话；从不同断点上的第n个子节点开始？

我正在使用Susy 2，我有以下代码：

@include breakpoint($tab) {
  .l-region--sections {
    > .block {
      @include span(6 of 12);
      &:nth-child(2n) {
        @include last;
      }
    }
  }
}

@include breakpoint($desk) {
  .l-region--sections {
    > .block {
      @include span(4 of 16);
      &:last-child {
        @include last;
      }
    }
  }
}

---

问题是，在桌面宽度上，“：nth child（2n）”生效，我想完全删除它，以支持“：last child”。如何删除桌面的“：nth child（2n）”样式？

答案似乎如下：，基本上：

@include breakpoint($tab) {
  .l-region--sections {
    > .block {
      @include span(6 of 12);
      &:nth-child(2n) {
        @include last;
      }
    }
  }
}

@include breakpoint($desk) {
  .l-region--sections {
    > .block {
      @include span(4 of 16);
      &:nth-child(2n) {
        @include span(4 of 16); // We are declaring span for this container here once more, just to override nth-child styles.
      }
      &:last-child {
        @include last;
      }
    }
  }
}