CSS inset soical icons

index.slim

a.icon-facebook href="#"
a.icon-twitter href="#"
a.icon-google-plus href="#"
a.icon-tumblr href="#"
a.icon-pinterest href="#"
a.icon-youtube href="#"
a.icon-instagram href="#"

style.css

html {
   height: 100%;
} 

body {
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex; 
  display: flex;

  -webkit-box-align: center; 
  -moz-box-align: center;
  -ms-flex-align: center;
  -webkit-align-items: center;
  align-items: center;

  -webkit-box-pack: center; 
  -moz-box-pack: center; 
  -ms-flex-pack: center; 
  -webkit-justify-content: center;
  justify-content: center;

  margin: 0;
  height: 100%;
  width: 100%; 
   
  background-color: #CBCBCB;
} 

a {
  padding: .5em 1em;
}
[class^="icon-"]:before,
[class*=" icon-"]:before {
  font-size: 5em;
  background-color: #666666;
  -webkit-background-clip: text;
  -moz-background-clip: text;
  background-clip: text;
  color: transparent;
  text-shadow: rgba(255,255,255,0.5) 0px 2px 3px;
  transition: all 0.5s ease;
}
[class^="icon-"]:hover:before,
[class*=" icon-"]:hover:before {
  text-shadow: rgba(0,0,0,.5) 0px 2px 3px;
}