If anybody is googling for this later:
<style>
html, body
{
height: 100%;
margin: 0;
}
body
{
display: flex;
display: -webkit-flex;
-webkit-justify-content: center;
justify-content: center;
-webkit-align-items: center;
align-items: center;
}
canvas
{
display: block;
outline: none;
height: 100%;
max-height: 133.333vw;
width: 100%;
max-width: 75vh;
}
</style>
worked well for my use case