html, body {
  margin: 0; padding: 0;
}

.fragment {
  overflow: hidden;
}

#sky {	
  display: flex;
  background: url("sky.png") repeat-x;
  height: 860px;
  width: 5076px;
  animation: slide 10s linear infinite;
  -webkit-animation: slide 10s linear infinite;
}

@-webkit-keyframes slide{
  0%{
    transform: translate3d(0, 0, 0);
  }
  100%{
    transform: translate3d(-1692px, 0, 0);
  }
}
.bird {
    z-index: 3;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}