div.circle-wrap
  - for (var x =1; x <= 12; x++)
    div.row
      - for (var y = 1; y <= 12; y++)
        div.circle

@mixin center {
  display : flex;
  align-items: center;
  justify-content: center;
}
body {
  @include center;
  height: 100vh;
  background-image: linear-gradient(45deg, #00DBDE 0%, #FC00FF 100%);
}
.row {
  display: flex;
  .circle {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    margin: 5px 10px;
    background: #fff;
    transform-origin : top center;
    animation : spin 1s linear infinite;
  }
  @keyframes spin {
    0% {transform : scale(1.1) rotate(0deg);}
    50% {transform : scale(0.2) rotate(180deg);}
    100% {transform : scale(1.1) rotate(360deg);}
  }
}
@for $i from 1 through 12 {
    .row:nth-child(#{$i}) .circle {animation-delay : 100ms * $i;}
}