With CSS only you could use a pseudoelement to keep always the aspect ratio to 1:1
or use the new
aspect-ratio
property , e.g.
.container {
display: grid;
grid-template-columns: 1fr 1fr 1fr 1fr;
grid-gap: 5px;
}
.container div {
background-color: red;
aspect-ratio: 1;
}
<div class="container">
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
</div>