md/assets/css/loading.css

.loading {
  text-align: center;
  position: fixed;
  width: 100%;
  height: 100%;
  overflow: hidden;
  z-index: 99999;
  background-color: #f2f2f2;
}

.loading_night {
  background-color: #303133;
}

.loading-wrapper {
  position: fixed;
  top: 50%;
  left: 50%;
  -webkit-transform: translateX(-50%) translateY(-50%);
  -moz-transform: translateX(-50%) translateY(-50%);
  -ms-transform: translateX(-50%) translateY(-50%);
  transform: translateX(-50%) translateY(-50%);
}

.loading-text {
  line-height: 1.4;
  font-size: 1.2rem;
  font-weight: bold;
  margin-bottom: 1rem;
}

.loading-anim {
  width: 35px;
  height: 35px;
  border: 5px solid rgba(189, 189, 189, 0.25);
  border-left-color: rgba(66, 185, 131, 0.9);
  border-top-color: rgba(66, 185, 131, 0.9);
  border-radius: 50%;
  display: inline-block;
  animation: rotate 600ms infinite linear;
}

@keyframes rotate {
  to {
    transform: rotate(1turn)
  }
}