Center div with max-width and height enabled and maintain aspect-ratio - html

Question

How can I center a div with max-width and max height, but also maintain it's aspect ratio?
My code so far centers div, but it does not maintain aspect ratio of 6:5 (height:width)
#main-content {
margin: 0 auto;
width: 100%;
max-width: 1200px;
height: 100%;
height: 500px;
background-color: #953d44;
position: relative;
}
#container {
width: 80%;
height: 80%;
max-height: 600px;
max-width: 500px;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
position: absolute;
background-color: cornflowerblue;
}
<div id="main-content">
<div id="container"></div>
</div>
https://codepen.io/timsim/pen/dWMbqR

Answer 1

You couldnt notice the change because the main container itself had only 500px height. I have changed it to 1000px.
Run the following snippet and goto full screen mode, It actually works!
#main-content {
margin: 0 auto;
width: 100%;
max-width: 1200px;
height: 100%;
height: 1000px;
background-color: #953d44;
position: relative;
}
#container {
width: 80%;
height: 80%;
max-height: 600px;
max-width: 500px;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
position: absolute;
background-color: cornflowerblue;
}
<div id="main-content">
<div id="container"></div>
</div>
P.S.: Ofc this wont work if main container height is less then the max height specified for the contanier.