POC of a share button full css/font

index.html

<h1>Hover it</h1>
<div class="main">
  <div class="rounded center icon-share"></div>
  <div class="share-container rounded">
    <a class="share-btn tl icon-google-plus" href='#'></a>    
    <a class="share-btn tr icon-twitter" href='#'></a>    
    <a class="share-btn bl icon-pinterest" href='#'></a>    
    <a class="share-btn br icon-facebook" href='#'></a>    
  </div>
</div>

style.css

body {
  background: radial-gradient(center, ellipse cover,  #fefefe 0%, #dbe5e7 100%); 
  background-attachment: fixed;
}

h1 {
  text-align: center;
  color: #56a6e4;
  font-size: 2em;
  font-weight: bold;
  padding: 5px;
  text-transform: uppercase;
}
a {
  text-decoration: none;
}
.main, .center, .center-bis {
  width: 32px;
  height: 32px;
}
.main {
  font: 14px, 'FontAwesome';
  position: relative;
  margin: 50px auto;
  
}
.rounded {
  border-radius: 50%;
  overflow: hidden;
  text-align: center;
}
.center {
  display: inline-block;
  vertical-align: middle;
  z-index: 5;
  position: relative;
  background: linear-gradient(#8df 0%, #29d 100%);
  box-shadow: 0 1px 5px rgba(255, 255, 255, 0.5) inset, 0 0 0px 1px rgba(33, 112, 178, 0.5);
  line-height: 33px;
  color: #fff;
  
}
.center img {    
  vertical-align: middle;
}


.share-btn {
  display:inline-block;
  width: 49%;
  height: 49%;
  position: absolute;
  z-indez:1;
  border-color: #92888f;
  border-style: solid;
  border-width: 0;
  font-size: 25px;
  color: #777777;
}
.share-btn:hover {
  background:linear-gradient(#8df 0%, #29d 100%);
  color: #ffffff;
  text-shadow: 0 -1px #4298e0;
}
.share-btn.tl {
  right: 50%;
  bottom: 50%;
  border-top-left-radius: 100%;
  
  text-indent: 5px;
  line-height: 55px;
  
}

.share-btn.tr {
  left: 50%;
  bottom: 50%;
  border-top-right-radius: 100%;
  
  line-height: 50px;
  
}
.share-btn.bl {
  right: 50%;
  top: 50%;
  border-bottom-left-radius: 100%;
  
  text-indent: 2px;
  line-height: 47px;
  
}
.share-btn.br {
  left: 50%;
  top: 50%;
  border-bottom-right-radius: 100%;
  
  line-height: 46px;
  text-indent: -2px;
  
}
.share-container {
  position: absolute;
  top: 50%;
  left: 50%;
  margin-left: 0px;
  margin-top:  0px;
  overflow: hidden;
  transition: all 0.3s cubic-bezier(.05,.93,.61,1.6);
  box-shadow: 0px 0px 20px -5px rgba(0, 0, 0, 0.5);
  width: 0px;
  height: 0px;
  background: #fff;
}

.center:hover ~ .share-container,
.share-container:hover {
  width: 100px;
  height: 100px;
  margin-left: -50px;
  margin-top: -50px;
}

.share-container:after,
.share-container:before {
  position: absolute;
  background:  linear-gradient(rgba(136, 221, 255, 0.5) 0%, rgba(34, 153, 221, 0.5) 50%, rgba(136, 221, 255, 0.5) 100%);
  z-index:4;
  margin: 0;
  transition: all 0.5s ease-in-out;
  content: ' ';
}

.share-container:before {
  background:  linear-gradient(left, rgba(136, 221, 255, 0.5) 0%, rgba(34, 153, 221, 0.5) 50%, rgba(136, 221, 255, 0.5) 100%);
  height: 1px;
  margin: 50% 50%;
  width: 0%;
}
.center:hover ~ .share-container:before,
.share-container:hover:before {
  width: 85%;
  left: 0px;
  margin: 50% 7%;
}


.share-container:after {
  left: -1px;
  height: 0%;
  width: 1px;
  margin: 50% 50%;
}
.center:hover ~ .share-container:after,
.share-container:hover:after {
  height: 85%;
  margin: 7% 50%;
}

/*  Font Awesome
    the iconic font designed for use with Twitter Bootstrap
    -------------------------------------------------------
    The full suite of pictographic icons, examples, and documentation
    can be found at: http://fortawesome.github.com/Font-Awesome/

    License
    -------------------------------------------------------
    The Font Awesome webfont, CSS, and LESS files are licensed under CC BY 3.0:
    http://creativecommons.org/licenses/by/3.0/ A mention of
    'Font Awesome - http://fortawesome.github.com/Font-Awesome' in human-readable
    source code is considered acceptable attribution (most common on the web).
    If human readable source code is not available to the end user, a mention in
    an 'About' or 'Credits' screen is considered acceptable (most common in desktop
    or mobile software).

    Contact
    -------------------------------------------------------
    Email: dave@davegandy.com
    Twitter: http://twitter.com/fortaweso_me
    Work: http://lemonwi.se co-founder

    */
@font-face{
    font-family:FontAwesome;
    src:url(http://netdna.bootstrapcdn.com/font-awesome/2.0/font//fontawesome-webfont.eot?#iefix) format('eot'),
    url(http://netdna.bootstrapcdn.com/font-awesome/2.0/font//fontawesome-webfont.woff) format('woff'),
    url(http://netdna.bootstrapcdn.com/font-awesome/2.0/font//fontawesome-webfont.ttf) format('truetype'),
    url(http://netdna.bootstrapcdn.com/font-awesome/2.0/font//fontawesome-webfont.svg#FontAwesome) format('svg');
    font-weight:400;font-style:normal;}


/*  Font Awesome styles
    ------------------------------------------------------- */
[class^="icon-"]:before, [class*=" icon-"]:before {
  font-family: FontAwesome;
  font-weight: normal;
  font-style: normal;
  display: inline-block;
  text-decoration: inherit;
}
a [class^="icon-"], a [class*=" icon-"] {
  display: inline-block;
  text-decoration: inherit;
}
/* makes the font 33% larger relative to the icon container */
.icon-large:before {
  vertical-align: top;
  font-size: 1.3333333333333333em;
}
.btn [class^="icon-"], .btn [class*=" icon-"] {
  /* keeps button heights with and without icons the same */

  line-height: .9em;
}
li [class^="icon-"], li [class*=" icon-"] {
  display: inline-block;
  width: 1.25em;
  text-align: center;
}
li .icon-large[class^="icon-"], li .icon-large[class*=" icon-"] {
  /* 1.5 increased font size for icon-large * 1.25 width */

  width: 1.875em;
}
li[class^="icon-"], li[class*=" icon-"] {
  margin-left: 0;
  list-style-type: none;
}
li[class^="icon-"]:before, li[class*=" icon-"]:before {
  text-indent: -2em;
  text-align: center;
}
li[class^="icon-"].icon-large:before, li[class*=" icon-"].icon-large:before {
  text-indent: -1.3333333333333333em;
}
/*  Font Awesome uses the Unicode Private Use Area (PUA) to ensure screen
    readers do not read off random characters that represent icons */
.icon-facebook:before             { content: "\f09a"; }
.icon-twitter:before              { content: "\f099"; }
.icon-pinterest:before            { content: "\f0d2"; }
.icon-google-plus:before          { content: "\f0d5"; }

.icon-share:before                { content: "\f045"; }
​