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 $i from 1 through 25 {
    .star-small:nth-of-type(#{$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;
  }
  25.81% {
    background-position: -24px 0px;
  }
  43.47% {
    background-position: 0px 0px;
  }
  59.63% {
    background-position: -24px 0px;
  }
}
.star-medium {
  background-image: url("https://i.imgur.com/fM1biij.png");
  animation: star-medium 9s infinite step-end;
  animation-delay: -1.4s;
}

@keyframes star-medium {
  0% {
    background-position: 0px 0px;
  }
  0.61% {
    background-position: -24px 0px;
  }
  20.72% {
    background-position: 0px 0px;
  }
  23.66% {
    background-position: -24px 0px;
  }
  25.17% {
    background-position: -48px 0px;
  }
  68.63% {
    background-position: -24px 0px;
  }
  84.76% {
    background-position: -48px 0px;
  }
}
.star-large {
  background-image: url("https://i.imgur.com/fM1biij.png");
  animation: star-large 9s infinite step-end;
  animation-delay: -7.4s;
}

.star-large-offset {
  animation-delay: -0.2s;
}

@keyframes star-large {
  0% {
    background-position: 0px 0px;
  }
  14.32% {
    background-position: -24px 0px;
  }
  21.28% {
    background-position: 0px 0px;
  }
  40.3% {
    background-position: -24px 0px;
  }
  56.13% {
    background-position: 0px 0px;
  }
  57.88% {
    background-position: -24px 0px;
  }
  83.83% {
    background-position: -48px 0px;
  }
}
.star-small:nth-of-type(1) {
  top: 61vh;
  left: 37vw;
}

.star-medium:nth-of-type(1) {
  top: 11vh;
  left: 40vw;
}

.star-large:nth-of-type(1) {
  top: 31vh;
  left: 19vw;
}

.star-small:nth-of-type(2) {
  top: 27vh;
  left: 96vw;
}

.star-medium:nth-of-type(2) {
  top: 71vh;
  left: 60vw;
}

.star-large:nth-of-type(2) {
  top: 5vh;
  left: 58vw;
}

.star-small:nth-of-type(3) {
  top: 1vh;
  left: 96vw;
}

.star-medium:nth-of-type(3) {
  top: 70vh;
  left: 76vw;
}

.star-large:nth-of-type(3) {
  top: 22vh;
  left: 80vw;
}

.star-small:nth-of-type(4) {
  top: 52vh;
  left: 47vw;
}

.star-medium:nth-of-type(4) {
  top: 20vh;
  left: 28vw;
}

.star-large:nth-of-type(4) {
  top: 5vh;
  left: 69vw;
}

.star-small:nth-of-type(5) {
  top: 100vh;
  left: 14vw;
}

.star-medium:nth-of-type(5) {
  top: 89vh;
  left: 22vw;
}

.star-large:nth-of-type(5) {
  top: 83vh;
  left: 9vw;
}

.star-small:nth-of-type(6) {
  top: 64vh;
  left: 35vw;
}

.star-medium:nth-of-type(6) {
  top: 6vh;
  left: 4vw;
}

.star-large:nth-of-type(6) {
  top: 7vh;
  left: 77vw;
}

.star-small:nth-of-type(7) {
  top: 47vh;
  left: 24vw;
}

.star-medium:nth-of-type(7) {
  top: 5vh;
  left: 81vw;
}

.star-large:nth-of-type(7) {
  top: 22vh;
  left: 87vw;
}

.star-small:nth-of-type(8) {
  top: 64vh;
  left: 37vw;
}

.star-medium:nth-of-type(8) {
  top: 45vh;
  left: 22vw;
}

.star-large:nth-of-type(8) {
  top: 63vh;
  left: 57vw;
}

.star-small:nth-of-type(9) {
  top: 11vh;
  left: 90vw;
}

.star-medium:nth-of-type(9) {
  top: 97vh;
  left: 97vw;
}

.star-large:nth-of-type(9) {
  top: 77vh;
  left: 77vw;
}

.star-small:nth-of-type(10) {
  top: 82vh;
  left: 58vw;
}

.star-medium:nth-of-type(10) {
  top: 32vh;
  left: 75vw;
}

.star-large:nth-of-type(10) {
  top: 53vh;
  left: 100vw;
}

.star-small:nth-of-type(11) {
  top: 100vh;
  left: 28vw;
}

.star-medium:nth-of-type(11) {
  top: 42vh;
  left: 83vw;
}

.star-large:nth-of-type(11) {
  top: 48vh;
  left: 17vw;
}

.star-small:nth-of-type(12) {
  top: 65vh;
  left: 5vw;
}

.star-medium:nth-of-type(12) {
  top: 67vh;
  left: 65vw;
}

.star-large:nth-of-type(12) {
  top: 31vh;
  left: 27vw;
}

.star-small:nth-of-type(13) {
  top: 49vh;
  left: 16vw;
}

.star-medium:nth-of-type(13) {
  top: 93vh;
  left: 34vw;
}

.star-large:nth-of-type(13) {
  top: 1vh;
  left: 85vw;
}

.star-small:nth-of-type(14) {
  top: 1vh;
  left: 13vw;
}

.star-medium:nth-of-type(14) {
  top: 73vh;
  left: 73vw;
}

.star-large:nth-of-type(14) {
  top: 86vh;
  left: 91vw;
}

.star-small:nth-of-type(15) {
  top: 35vh;
  left: 84vw;
}

.star-medium:nth-of-type(15) {
  top: 33vh;
  left: 3vw;
}

.star-large:nth-of-type(15) {
  top: 89vh;
  left: 29vw;
}

.star-small:nth-of-type(16) {
  top: 22vh;
  left: 7vw;
}

.star-medium:nth-of-type(16) {
  top: 3vh;
  left: 92vw;
}

.star-large:nth-of-type(16) {
  top: 58vh;
  left: 32vw;
}

.star-small:nth-of-type(17) {
  top: 67vh;
  left: 23vw;
}

.star-medium:nth-of-type(17) {
  top: 15vh;
  left: 43vw;
}

.star-large:nth-of-type(17) {
  top: 86vh;
  left: 95vw;
}

.star-small:nth-of-type(18) {
  top: 48vh;
  left: 94vw;
}

.star-medium:nth-of-type(18) {
  top: 62vh;
  left: 85vw;
}

.star-large:nth-of-type(18) {
  top: 8vh;
  left: 5vw;
}

.star-small:nth-of-type(19) {
  top: 17vh;
  left: 39vw;
}

.star-medium:nth-of-type(19) {
  top: 92vh;
  left: 19vw;
}

.star-large:nth-of-type(19) {
  top: 10vh;
  left: 14vw;
}

.star-small:nth-of-type(20) {
  top: 6vh;
  left: 24vw;
}

.star-medium:nth-of-type(20) {
  top: 33vh;
  left: 78vw;
}

.star-large:nth-of-type(20) {
  top: 4vh;
  left: 49vw;
}

.star-small:nth-of-type(21) {
  top: 89vh;
  left: 70vw;
}

.star-medium:nth-of-type(21) {
  top: 3vh;
  left: 98vw;
}

.star-large:nth-of-type(21) {
  top: 74vh;
  left: 16vw;
}

.star-small:nth-of-type(22) {
  top: 89vh;
  left: 21vw;
}

.star-medium:nth-of-type(22) {
  top: 87vh;
  left: 14vw;
}

.star-large:nth-of-type(22) {
  top: 2vh;
  left: 17vw;
}

.star-small:nth-of-type(23) {
  top: 32vh;
  left: 71vw;
}

.star-medium:nth-of-type(23) {
  top: 88vh;
  left: 64vw;
}

.star-large:nth-of-type(23) {
  top: 73vh;
  left: 61vw;
}

.star-small:nth-of-type(24) {
  top: 76vh;
  left: 64vw;
}

.star-medium:nth-of-type(24) {
  top: 55vh;
  left: 71vw;
}

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

.star-small:nth-of-type(25) {
  top: 99vh;
  left: 42vw;
}

.star-medium:nth-of-type(25) {
  top: 10vh;
  left: 71vw;
}

.star-large:nth-of-type(25) {
  top: 73vh;
  left: 50vw;
}

settings.json

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