Example

by Christian Sonne

HTML

<!-- Learn about this code on MDN: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-columns -->

<div id="grid">
  <div id="item1"></div>
  <div id="item2"></div>
  <div id="item3"></div>
</div>

CSS

#grid {
  height: 100px;
  display: grid;
  grid-template-areas: "a a";
  grid-gap: 10px;
  grid-auto-columns: 200px;
}

#grid > div {
  background-color: lime;
}