Generated by SassMeister.com.

input.scss

@function quick-sort($list) {
  $less:  ();
  $equal: ();
  $large: ();

  @if length($list) > 1 {
    $seed: nth($list, ceil(length($list) / 2));

    @each $item in $list {
      @if ($item == $seed) {
        $equal: append($equal, $item);
      } @else if ($item < $seed) {
        $less: append($less, $item);
      } @else if ($item > $seed) {
        $large: append($large, $item);
      }
    }

    @return join(join(quick-sort($less), $equal), quick-sort($large));
  }

  @return $list;
}

.star-small, .star-medium, .star-large {
    width: 24px;
    height: 24px;
    position: fixed;
    background-size: auto 24px;
    background-position: 0px 0px;
    image-rendering: crisp-edges;
    z-index: -5;
}

.star-small {
    background-image: url('https://i.imgur.com/VQJRbzZ.png');
    animation: star-small 6s infinite step-end;
}

$small-percents: quick-sort([random(10000)/10000, random(10000)/10000, random(10000)/10000]);
$small-positions: -24px, 0px, -24px;

@keyframes star-small {
	0% { background-position: 0px 0px; }
	@for $i from 1 through 3 {
    	#{percentage(nth($small-percents, $i))} {
    	    background-position: #{nth($small-positions, $i)} 0px;
    	}
	}
}

$medium-percents: ();
$medium-positions: (1);
@for $i from 1 through 6 {
    $medium-percents: append($medium-percents, random(10000)/10000);
    @if nth($medium-positions, -1) == 0 or nth($medium-positions, -1) == 2 {
        $medium-positions: append($medium-positions, 1);
    } @else if random() < 0.5 {
        $medium-positions: append($medium-positions, 2);
    } @else {
        $medium-positions: append($medium-positions, 0);
    }
}
$medium-percents: quick-sort($medium-percents);

.star-medium {
    background-image: url('https://i.imgur.com/fM1biij.png');
    animation: star-medium 9s infinite step-end;
    animation-delay: (random(90) / 10) * -1s;
}

@keyframes star-medium {
	0% { background-position: 0px 0px; }
	@for $i from 1 through 6 {
    	#{percentage(nth($medium-percents, $i))} {
    	    background-position: #{nth($medium-positions, $i) * -24px} 0px;
    	}
	}
}

$large-percents: ();
$large-positions: (1);
@for $i from 1 through 6 {
    $large-percents: append($large-percents, random(10000)/10000);
    @if nth($large-positions, -1) == 0 or nth($large-positions, -1) == 2 {
        $large-positions: append($large-positions, 1);
    } @else if random() < 0.5 {
        $large-positions: append($large-positions, 2);
    } @else {
        $large-positions: append($large-positions, 0);
    }
}
$large-percents: quick-sort($large-percents);

.star-large {
    background-image: url('https://i.imgur.com/fM1biij.png');
    animation: star-large 9s infinite step-end;
    animation-delay: (random(90) / 10) * -1s;
}

.star-large-offset {
    animation-delay: (random(90) / 10) * -1s;
}

@keyframes star-large {
	0% { background-position: 0px 0px; }
	@for $i from 1 through 6 {
    	#{percentage(nth($large-percents, $i))} {
    	    background-position: #{nth($large-positions, $i) * -24px} 0px;
    	}
	}
}

@for $i from 1 through 20 {
    .star-small:nth-of-type(#{$i}) {
        top: random(100) + vh;
        left: random(100) + vw;
    }
    .star-medium:nth-of-type(#{$i}) {
        top: random(100) + vh;
        left: random(100) + vw;
    }
    .star-large:nth-of-type(#{$i}) {
        top: random(100) + vh;
        left: random(100) + vw;
    }
}

output.css

.star-small, .star-medium, .star-large {
  width: 24px;
  height: 24px;
  position: fixed;
  background-size: auto 24px;
  background-position: 0px 0px;
  image-rendering: crisp-edges;
  z-index: -5;
}

.star-small {
  background-image: url("https://i.imgur.com/VQJRbzZ.png");
  animation: star-small 6s infinite step-end;
}

@keyframes star-small {
  0% {
    background-position: 0px 0px;
  }
  13.86% {
    background-position: -24px 0px;
  }
  33.93% {
    background-position: 0px 0px;
  }
  97.43% {
    background-position: -24px 0px;
  }
}
.star-medium {
  background-image: url("https://i.imgur.com/fM1biij.png");
  animation: star-medium 9s infinite step-end;
  animation-delay: -1.8s;
}

@keyframes star-medium {
  0% {
    background-position: 0px 0px;
  }
  11.43% {
    background-position: -24px 0px;
  }
  21.51% {
    background-position: 0px 0px;
  }
  23.11% {
    background-position: -24px 0px;
  }
  26.69% {
    background-position: 0px 0px;
  }
  66.22% {
    background-position: -24px 0px;
  }
  82.48% {
    background-position: 0px 0px;
  }
}
.star-large {
  background-image: url("https://i.imgur.com/fM1biij.png");
  animation: star-large 9s infinite step-end;
  animation-delay: -8.4s;
}

.star-large-offset {
  animation-delay: -7.4s;
}

@keyframes star-large {
  0% {
    background-position: 0px 0px;
  }
  6.21% {
    background-position: -24px 0px;
  }
  23.58% {
    background-position: 0px 0px;
  }
  24.06% {
    background-position: -24px 0px;
  }
  52.02% {
    background-position: -48px 0px;
  }
  91.01% {
    background-position: -24px 0px;
  }
  92.43% {
    background-position: 0px 0px;
  }
}
.star-small:nth-of-type(1) {
  top: 68vh;
  left: 94vw;
}

.star-medium:nth-of-type(1) {
  top: 39vh;
  left: 48vw;
}

.star-large:nth-of-type(1) {
  top: 49vh;
  left: 58vw;
}

.star-small:nth-of-type(2) {
  top: 73vh;
  left: 24vw;
}

.star-medium:nth-of-type(2) {
  top: 5vh;
  left: 19vw;
}

.star-large:nth-of-type(2) {
  top: 8vh;
  left: 39vw;
}

.star-small:nth-of-type(3) {
  top: 29vh;
  left: 7vw;
}

.star-medium:nth-of-type(3) {
  top: 78vh;
  left: 93vw;
}

.star-large:nth-of-type(3) {
  top: 64vh;
  left: 55vw;
}

.star-small:nth-of-type(4) {
  top: 49vh;
  left: 26vw;
}

.star-medium:nth-of-type(4) {
  top: 82vh;
  left: 82vw;
}

.star-large:nth-of-type(4) {
  top: 84vh;
  left: 59vw;
}

.star-small:nth-of-type(5) {
  top: 56vh;
  left: 88vw;
}

.star-medium:nth-of-type(5) {
  top: 23vh;
  left: 11vw;
}

.star-large:nth-of-type(5) {
  top: 5vh;
  left: 27vw;
}

.star-small:nth-of-type(6) {
  top: 65vh;
  left: 7vw;
}

.star-medium:nth-of-type(6) {
  top: 35vh;
  left: 66vw;
}

.star-large:nth-of-type(6) {
  top: 9vh;
  left: 89vw;
}

.star-small:nth-of-type(7) {
  top: 55vh;
  left: 79vw;
}

.star-medium:nth-of-type(7) {
  top: 16vh;
  left: 16vw;
}

.star-large:nth-of-type(7) {
  top: 94vh;
  left: 48vw;
}

.star-small:nth-of-type(8) {
  top: 27vh;
  left: 89vw;
}

.star-medium:nth-of-type(8) {
  top: 74vh;
  left: 1vw;
}

.star-large:nth-of-type(8) {
  top: 68vh;
  left: 49vw;
}

.star-small:nth-of-type(9) {
  top: 83vh;
  left: 73vw;
}

.star-medium:nth-of-type(9) {
  top: 58vh;
  left: 80vw;
}

.star-large:nth-of-type(9) {
  top: 34vh;
  left: 68vw;
}

.star-small:nth-of-type(10) {
  top: 36vh;
  left: 47vw;
}

.star-medium:nth-of-type(10) {
  top: 14vh;
  left: 14vw;
}

.star-large:nth-of-type(10) {
  top: 33vh;
  left: 38vw;
}

.star-small:nth-of-type(11) {
  top: 69vh;
  left: 24vw;
}

.star-medium:nth-of-type(11) {
  top: 6vh;
  left: 7vw;
}

.star-large:nth-of-type(11) {
  top: 74vh;
  left: 83vw;
}

.star-small:nth-of-type(12) {
  top: 78vh;
  left: 64vw;
}

.star-medium:nth-of-type(12) {
  top: 83vh;
  left: 28vw;
}

.star-large:nth-of-type(12) {
  top: 46vh;
  left: 4vw;
}

.star-small:nth-of-type(13) {
  top: 1vh;
  left: 44vw;
}

.star-medium:nth-of-type(13) {
  top: 69vh;
  left: 54vw;
}

.star-large:nth-of-type(13) {
  top: 7vh;
  left: 27vw;
}

.star-small:nth-of-type(14) {
  top: 46vh;
  left: 35vw;
}

.star-medium:nth-of-type(14) {
  top: 41vh;
  left: 99vw;
}

.star-large:nth-of-type(14) {
  top: 39vh;
  left: 36vw;
}

.star-small:nth-of-type(15) {
  top: 94vh;
  left: 98vw;
}

.star-medium:nth-of-type(15) {
  top: 89vh;
  left: 41vw;
}

.star-large:nth-of-type(15) {
  top: 71vh;
  left: 28vw;
}

.star-small:nth-of-type(16) {
  top: 18vh;
  left: 45vw;
}

.star-medium:nth-of-type(16) {
  top: 65vh;
  left: 76vw;
}

.star-large:nth-of-type(16) {
  top: 29vh;
  left: 90vw;
}

.star-small:nth-of-type(17) {
  top: 63vh;
  left: 94vw;
}

.star-medium:nth-of-type(17) {
  top: 58vh;
  left: 46vw;
}

.star-large:nth-of-type(17) {
  top: 28vh;
  left: 78vw;
}

.star-small:nth-of-type(18) {
  top: 42vh;
  left: 51vw;
}

.star-medium:nth-of-type(18) {
  top: 44vh;
  left: 4vw;
}

.star-large:nth-of-type(18) {
  top: 54vh;
  left: 62vw;
}

.star-small:nth-of-type(19) {
  top: 98vh;
  left: 1vw;
}

.star-medium:nth-of-type(19) {
  top: 98vh;
  left: 42vw;
}

.star-large:nth-of-type(19) {
  top: 36vh;
  left: 85vw;
}

.star-small:nth-of-type(20) {
  top: 39vh;
  left: 96vw;
}

.star-medium:nth-of-type(20) {
  top: 60vh;
  left: 28vw;
}

.star-large:nth-of-type(20) {
  top: 12vh;
  left: 44vw;
}

settings.json

{
  "sass": {
    "compiler": "dart-sass/1.26.11",
    "extensions": {},
    "syntax": "SCSS",
    "outputStyle": "expanded"
  },
  "autoprefixer": false
}