TV snow effect

snow.scss

@function random-gray(){
  $col:random(5);
  @return rgb($col * 51, $col * 51, $col * 51);
}

@function grid-dots(){
  $sh:();
  @for $j from 1 through 20 {
    @for $i from 1 through 20 {
      $sh: $sh, (($i*10px)-(10px)) (($j*10px)-(10px)) 0 random-gray();
   }
  }
  @return $sh;
}

.snow {
  margin: auto;
  width: 200px;
  height: 200px;
  
  &:before{
    content:'';
    position: absolute;
    width: 10px;
    height: 10px;
    background: black;
    box-shadow: grid-dots();
    animation: snow 1.5s linear infinite; 
  }
}

@keyframes snow {
  @for $i from 1 through 10{
    #{$i*10}% { box-shadow: grid-dots(); }
  }
}