gistfile1.css

@media only screen and (-webkit-min-device-pixel-ratio: 2) {  
  img[src="images/icon.png"] {
    content: url("images/icon@2x.png");
  }
  img[src="images/store_small.png"] {
    content: url("images/store_small@2x.png");
  }
  img[src="images/screen_fail.png"] {
    content: url("images/screen_fail@2x.png");
  }
  img[src="images/screen_play.png"] {
    content: url("images/screen_play@2x.png");
  }
}