Preserving comment section width on mobile only

Site URL: http://www.figandlight.com

Hello!

I found a way to adjust the width of the comment section on a blog post to make it smaller than the page width. But that change carries over into the mobile layout as well. Is there a way to apply the width change to ONLY the desktop version of the site but not the mobile version?

Here's the code I used: 

.squarespace-comments {
    width: 75%;
    margin: 0 auto;
}

Any help would be appreciated, thank you!

Edit code to this

/* desktop comment width */
@media screen and (min-width:768px) {
.squarespace-comments {
    width: 75%;
    margin: 0 auto;
}
}

It worked! Thank you so much!!