<div class='container'>
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
  <div class="item">4</div>
  <div class="item">5</div>
  <div class="item">6</div>
</div>

html,
body {
  background: GhostWhite;
  margin: 0;
}

.container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  grid-auto-rows: 100px;
  grid-gap: 2rem;
  padding: 2rem;
}

.item {
  background: MidnightBlue;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 2rem;
  color: MediumSpringGreen;
  font-family: sans-serif;
  box-shadow: 6px 10px 15px -3px rgba(0, 0, 0, 0.1);
  border-radius: 8px;
}