<div class="container">
<div class="panel"></div>
</div>
.container {
width: 50%;
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}
.panel {
background-color: red;
width: 100%;
padding-top: 75%;
}
This Pen doesn't use any external CSS resources.
This Pen doesn't use any external JavaScript resources.