How do I make wallpaper image resize to screen size (i.e. phone, tablet & desktop)?

The wallpaper background on our site does not resize to screen size. The wallpaper looks good on a desktop, but is too big when viewing on a phone (see images below). Is there a way to get the wallpaper to resize to the screen size? The code I am using for the wallpaper is:

.page-container {

background-image: url({{ ‘LAFACE-wp-2.png’ | asset_url }});
background-color: $color-body;
background-repeat: no-repeat;
background-position: top center;
background-attachment: fixed;
-webkit-background-size: cover;
-moz-background-size: cover;-o-background-size: cover;
background-size: cover
}

The site is: https://laface-skin-care.myshopify.com/?_ab=0&_fd=0&_sc=1&key=a2a35434a549b03ad233264794405b77106e714c7d9528442a82aae4c696697d

Any help is appreciated!

DESKTOP:

PHONE: