Sass-父选择器？？？自身选择器

#outside{
    width: 61.8%;
    height: 200px;
    background-color: grey;
}

.inside{
    color: white;
    background: purple;
    border-radius: 5px;
    font-size: 20px;
    font-weight: bolder;
    text-align: center;
    display: block;
    &:hover{
        color: yellow;
    }
}

#outside {
  width: 61.8%;
  height: 200px;
  background-color: grey; }

.inside {
  color: white;
  background: purple;
  border-radius: 5px;
  font-size: 20px;
  font-weight: bolder;
  text-align: center;
  display: block; }
  .inside:hover {
    color: yellow; }