12 column grid example 2 mobile first (Interactive Example)

<!doctype html>
<title>Example</title>
<style>
  .grid {
    display: block;
  }
  .box {
    color: white;
    padding: 7px;
    background: yellowgreen;
    margin: 10px 0;
    text-align: center;
  }
  @media screen and (min-width: 576px) {
    .grid {
      display: grid;
      grid-template-rows: repeat(6, 1fr);
      grid-template-columns: repeat(12, 1fr);
      grid-gap: 10px;
    }
    .box {
      margin: 0;
    }
    .box:nth-child(2),
    .box:nth-child(21) {
      grid-column: span 11;
      }
    .box:nth-child(3),
    .box:nth-child(20) {
      grid-column: span 2;
      }
    .box:nth-child(4),
    .box:nth-child(19) {
      grid-column: span 10;
      }
    .box:nth-child(5),
    .box:nth-child(18) {
      grid-column: span 3;
      }
    .box:nth-child(6),
    .box:nth-child(17) {
      grid-column: span 9;
      }
    .box:nth-child(7),
    .box:nth-child(16) {
      grid-column: span 4;
      }
    .box:nth-child(8),
    .box:nth-child(15) {
      grid-column: span 8;
      }
    .box:nth-child(9),
    .box:nth-child(14) {
      grid-column: span 5;
      }
    .box:nth-child(10),
    .box:nth-child(13) {
      grid-column: span 7;
      }
    .box:nth-child(11),
    .box:nth-child(12) {
      grid-column: span 6;
      }
  }
</style>
<main class="grid">
  <div class="box">1</div>
  <div class="box">2</div>
  <div class="box">3</div>
  <div class="box">4</div>
  <div class="box">5</div>
  <div class="box">6</div>
  <div class="box">7</div>
  <div class="box">8</div>
  <div class="box">9</div>
  <div class="box">10</div>
  <div class="box">11</div>
  <div class="box">12</div>
  <div class="box">13</div>
  <div class="box">14</div>
  <div class="box">15</div>
  <div class="box">16</div>
  <div class="box">17</div>
  <div class="box">18</div>
  <div class="box">19</div>
  <div class="box">20</div>
  <div class="box">21</div>
  <div class="box">22</div>
</main>