fog-down-2x.css

html, body {
  margin: 0;
  padding: 0;
}
body {
  /*background-color: gray;*/
  background-image: url(mountains.png);
  overflow-x: hidden; 
}

/* ---------- Fog ---------- */
.fogwrapper {
  height: 100%;
  position: absolute;
  top: 0;
  width: 100%;
  filter: blur(1px) grayscale(0.7) saturate(1.9) sepia(0.2);
}
#foglayer_01, #foglayer_02, #foglayer_03 {
  height: 100%;
  position: absolute;
  width: 200%;
}
#foglayer_01 .image01, #foglayer_01 .image02,
#foglayer_02 .image01, #foglayer_02 .image02,
#foglayer_03 .image01, #foglayer_03 .image02 {
  float: left;
  height: 100%;
  width: 50%;
}
#foglayer_01 {
  animation: foglayer_01_opacity 10s linear infinite, foglayer_moveme 6s linear infinite;
}
#foglayer_02, #foglayer_03 {
  animation: foglayer_02_opacity 21s linear infinite, foglayer_moveme 2s linear infinite;
}

/* ---------- Moving Fog ---------- */
/*
  'size: cover' || 'size: 100%'; results remain the same
  'attachment: scroll' can be added or removed; results remain the same
  'attachment: fixed' causing unexpected results in Chrome
  'repeat-x' || 'no-repeat'; results remain the same
*/ 
#foglayer_01 .image01, #foglayer_01 .image02 {
  background: url("fog1.png") center center/cover no-repeat transparent;
}
#foglayer_02 .image01, #foglayer_02 .image02,
#foglayer_03 .image01, #foglayer_03 .image02{
  background: url("fog2.png") center center/cover no-repeat transparent;
}

/* ---------- Keyframe Layer 1 ---------- */
@keyframes foglayer_01_opacity {
  0% { opacity: .1; }
  22% { opacity: .5; }
  40% { opacity: .28; }
  58% { opacity: .4; }
  80% { opacity: .16; }
  100% { opacity: .1; }
}
/* ---------- Keyframe Layer 2 ---------- */
@keyframes foglayer_02_opacity {
  0% { opacity: .5; }
  25% { opacity: .2; }
  50% { opacity: .1; }
  80% { opacity: .3; }
  100% { opacity: .5; }
}
/* ---------- Keyframe Layer 3 ---------- */
@keyframes foglayer_03_opacity {
  0% { opacity: .8; }
  27% { opacity: .2; }
  52% { opacity: .6; }
  68% { opacity: .3; }
  100% { opacity: .8; }
}
/* ---------- Keyframe moveMe ---------- */
@keyframes foglayer_moveme {
  0% { top: -100%; }
  100% { top: 0; }
}