<div class="grid grow-melt">
  <div class="grid-item"></div>
  <div class="grid-item"></div>
  <div class="grid-item"></div>
  <div class="grid-item"></div>
  <div class="grid-item"></div>
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  <div class="grid-item"></div>
  <div class="grid-item"></div>
  <div class="grid-item"></div>
  <div class="grid-item"></div>
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</div>

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  margin: 0;
  background: #222;
}

:root {
  --blue-color-1: #6ee1f5;
}

// 绝对值
@function abs($v) {
  @return max(#{$v}, calc(-1 * #{$v}));
}

// 中位数
@function middle($v) {
  @return calc(0.5 * (#{$v} - 1));
}

// 数轴上两点距离
@function dist-1d($v1, $v2) {
  $v-delta: calc(#{$v1} - #{$v2});
  @return #{abs($v-delta)};
}

.grid {
  $row: 8;
  $col: 8;
  --row: #{$row};
  --col: #{$col};
  --gap: 0.25vw;

  display: grid;
  gap: var(--gap);
  grid-template-rows: repeat(var(--row), 1fr);
  grid-template-columns: repeat(var(--col), 1fr);

  &-item {
    --p: 2vw;
    --bg: var(--blue-color-1);

    @for $y from 1 through $row {
      @for $x from 1 through $col {
        $k: $col * ($y - 1) + $x;
        &:nth-child(#{$k}) {
          --x: #{$x};
          --y: #{$y};
        }
      }
    }

    padding: var(--p);
    box-shadow: inset 0 0 0 var(--p) var(--bg);
  }
  &.grow-melt {
    .grid-item {
      --t: 2s;

      animation-name: grow, melt;
      animation-duration: var(--t);
      animation-iteration-count: infinite;
    }
  }
}