<div class="spinner">
  <span class="spinner-circle _no1"></span>
  <span class="spinner-circle _no2"></span>
  <span class="spinner-circle _no3"></span>
</div>

.spinner {
  display: flex;
  place-content: center;
  column-gap: 10px;
  margin-top: 50px;
  position: relative;
  
  &-circle {
    width: 15px;
    height: 15px;
    border-radius: 50%;
    animation: fadeColor infinite 3s;
    
    @for $i from 1 to 4 {
      &._no#{$i} {
        animation-delay: $i * 1s;
    top: -20px;
      }
    }
  }
}

@keyframes fadeColor {
  from {
    background-color: gray;
    position: relative;
    top: 0;
  }
  to {
    background-color: #ddd;
  }
}