Using 2x images as sprite sheet.

style.css

/* sprite is 500x500 by default */
.sprite {
  background: url(sprites.png) top left no-repeat;
}

.sprite.sprite-user {
  background-position: 0px -100px;
}

/* Use the @2x sprite (1000x1000) only if the browser is capable of high-res display */
@media only screen and (-webkit-min-device-pixel-ratio: 1.5) {
  .sprite {
    background-image: sprites_2x.png;
    -webkit-background-size: 500px 500px;   
  }
}