zoro-cli/lib/plugins/config-web/template/src/style/transition/fade-in-out.css

https://github.com/vuejs/vue-cli

.fade-in-out-enter-active,
.fade-in-out-leave-active {
  transition: all 0.25s ease-in-out;
}

.fade-in-out-enter,
.fade-in-out-leave-to {
  opacity: 0.5;
}