@media
only screen and (-webkit-min-device-pixel-ratio: 2),
only screen and (   min--moz-device-pixel-ratio: 2),
only screen and (     -o-min-device-pixel-ratio: 2/1),
only screen and (        min-device-pixel-ratio: 2),
only screen and (                min-resolution: 192dpi),
only screen and (                min-resolution: 2dppx) {
    /* Comments */
    .comment .avatar > .mask {
        background-image: url('../img/avatar-mask@2x.png');
    }
    body.dark .comment .avatar > .mask {
        background-image: url('../img/avatar-mask-dark@2x.png');
    }
}