source: https://ryanbenhase.com/easily-implement-2x-retina-background-images/
@media all and (-webkit-min-device-pixel-ratio: 1.5), all and (-o-min-device-pixel-ratio: 3/2), all and (min--moz-device-pixel-ratio: 1.5), all and (min-device-pixel-ratio: 1.5)