$n: 180; 


html, body{
  width: 100%;
  height: 100%;
  float: left;
  overflow-x: hidden;
  background: #222;
}
header{
  position: fixed;  
  text-align: center;
  width: 100%;
  height: 300px;
  background: #333;
  color: #fff;
}

.scroll{
  width: 100%;
  height: 0;
  top: 0;
  
  width: 50%;
  height: 50%; 
  max-height: 200px;
  max-width: 200px;
  overflow: hidden;
  left: 50%;
  top: 50%;
  transform: translate(-50%,-50%) scale(1.2);
  position: absolute;


  .block{
    width: 10px;
    height: 10px;
    float: left;
    background: rebeccapurple; 
    display: block;
    margin: 2px;
    transition: transform 1s ease;
    animation: pump 3s ease infinite;
    position: relative; 
    @for $i from 0 through $n { 
      &:nth-child(#{($i)}){
        animation: pump 1s linear  $i/14.5+s infinite;  
      } 
  }
} 
}
.space{
  height: 1000px;
  display: block;
}


@keyframes pump{
  33%{
    border-radius: 100%;
    background: rebeccapurple;
  }
  66%{
    transform: scale(.2);
    background: #fff;
    box-shadow: 0 0 0 6px black;
  }
  100%{
    transform: rotate(90deg);

    //filter: invert(100%);
  }
}