Code Tuyết rơi cho website bằng CSS

<!-- Begin Code Tuyết rơi -->
<style type='text/css'>
.snow-container{position:fixed;width:100%;max-width:100%;z-index:99999;pointer-events:none;overflow:hidden;top:0;height:100%}
.snow{display:block;position:absolute;z-index:2;top:0;right:0;bottom:0;left:0;pointer-events:none;-webkit-transform:translate3d(0,-100%,0);transform:translate3d(0,-100%,0);-webkit-animation:snow linear infinite;animation:snow linear infinite}
.snow.foreground{background-image:url("https://i.imgur.com/Mc93itw.png");-webkit-animation-duration:15s;animation-duration:10s}
.snow.foreground.layered{-webkit-animation-delay:7.5s;animation-delay:7.5s}
.snow.middleground{background-image:url(https://i.imgur.com/0lSmBnC.png);-webkit-animation-duration:20s;animation-duration:15s}
.snow.middleground.layered{-webkit-animation-delay:10s;animation-delay:10s}
.snow.background{background-image:url(https://i.imgur.com/ra8kRtU.png);-webkit-animation-duration:25s;animation-duration:20s}
.snow.background.layered{-webkit-animation-delay:12.5s;animation-delay:12.5s}
@-webkit-keyframes snow{0%{-webkit-transform:translate3d(0,-100%,0);transform:translate3d(0,-100%,0)}100%{-webkit-transform:translate3d(5%,100%,0);transform:translate3d(5%,100%,0)}}
@keyframes snow{0%{-webkit-transform:translate3d(0,-100%,0);transform:translate3d(0,-100%,0)}100%{-webkit-transform:translate3d(5%,100%,0);transform:translate3d(5%,100%,0)}}
</style>
<div class='snow-container'><div class='snow foreground'></div><div class='snow foreground layered'></div><div class='snow middleground'></div><div class='snow middleground layered'></div><div class='snow background'></div><div class='snow background layered'></div></div>
<!-- End Code Tuyết rơi -->

Demo hình ảnh: