<a href="#" class="button"><span>詳しく見る</span></a>

.button {
  margin-bottom: 40px;
  height: 50px;
  width: 150px;
  display: grid;
  place-items: center;
  color: #fff;
  text-decoration: none;
  background-color: #000;
  position: relative;
  transition: all 0.6s ease;
  border: 1px solid #000;
  overflow: hidden;
  background-color: #000;
  position: relative;
  color: #fff;
  &::before {
    content: "";
    height: 50px;
    width: 150px;
    display: block;
    position: absolute;
    transform: translateX(-100%);
    background-color: #fff;
    transition: all 0.3s ease;
  }
  span {
    position: relative;
    z-index: 1;
  }
  &:hover {
    &::before {
      transform: translateX(0);
    }
    span {
      color: #000;
    }
  }
}