3 responsive columns

dabblet.css

/* 3 responsive columns */

@media all and (min-width: 1080px) {
  .box {
    float: left;
  }
  .box:nth-child(-n+2) {
    margin-right: 1em;
  }
  .box-container {
    display: flex;
    align-items: center;
    justify-content: center;
  }
}

@media all and (max-width: 1079px) {
  .box {
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 1em;
    position: relative;
    clear: both;
    display: block;
  }
  .box-container {
    display: block;
    clear: both;
    margin-left: auto;
    margin-right: auto;
    text-align: center;
  }
}

.box {
  width: 20em;
  height: 15em;
  border: 1px solid #000000;
  box-shadow: 0 0 1px rgba(0, 0, 0, 0.7);
  text-align: center;
}

.box-container {
  position: relative;
}

dabblet.html

<div class="box-container">
  <div class="box">
    1
  </div>
  <div class="box">
    2
  </div>
  <div class="box">
    3
  </div>
</div>

dabblet.js

// alert('Hello world!');

settings.json

{"view":"split","fontsize":"100","seethrough":"","prefixfree":"1","page":"all"}