:root {
  --back-top-color: #fff;
  --back-top-bg-color: #00a0ff;
}

.back-top-enter-active,
.back-top-leave-active {
  transition: opacity 0.3s;
}

.back-top-enter-from,
.back-top-leave-to {
  opacity: 0;
}

.back-top {
  position: fixed;
  right: 4rem;
  bottom: 3rem;
  box-sizing: border-box;
  cursor: pointer;
  height: 2.5rem;
  width: 2.5rem;
  z-index: 10;
  overflow: hidden;
}

.back-top .box {
  height: 2.5rem;
  width: 2.5rem;
  line-height: 2.5rem;
  border-radius: 50%;
  background-color: var(--back-top-bg-color);
  color: var(--back-top-color);
  display: flex;
  justify-content: center;
  align-items: center;
}

@media (max-width: 1199.98px) {
  .back-top {
    right: 1.5rem;
    bottom: 1.5rem;
  }
}