<div class="container">
  <div class="side-1">Side 1</div>  
  <div class="content">Content<br>…<br>…<br>…</div>
  <div class="side-2">Side 2</div>  
</div>

.container > * {
  margin-bottom: .5em;
}

.container > :last-child {
  margin: 0;
}

@media screen and (min-width: 600px) {
  .container {
    display: grid;
    grid-template-columns: 1fr 3fr 1fr;
    gap: 0.5rem;
  }
  
  .container > * {
    margin-bottom: 0;
  }
}

/* etc: */

.container > * {
  padding: 1em;
  background: #b3e888;
}

.container {
  background: #fff;
  padding: 1em;
}

body {
  padding: 1em;
  background: silver;
}

External CSS

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External JavaScript

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