<div id="grid">
  <div class="column"></div>
  <div class="column"></div>
  <div class="column"></div>
</div>

body {
  margin: 0;
  background: navajowhite;
}

#grid {
  height: 100vh;
  transition: 300ms;
  display: grid;
  grid-template-columns: 1fr 1fr 0fr;
}

#grid:hover {
  grid-template-columns: 1fr 1fr 1fr;
}

.column {
  outline: 1.5px solid rgb(0 0 0 / 10%);
}