.bg {
  background: #fff url(http://junxu.com/img/bg_img/code480.jpg) top center no-repeat;
  width: 400px;
  height: 400px;
}

a:link, a:visited {
  width: 200px;
  height: 200px;
  top: 50%;
  left: 50%;
  margin: 100px 0 0 100px;
  display: inline-block;
  color: rgba(255, 255, 255, 1.0);
  text-decoration: none;
  border-radius: 100px;
  text-align: right;
  text-shadow: 1px 1px 2px rgba(0, 0, 0, 1.0);
  -webkit-transition: all .5s ease-out;
  -moz-transition: all .5s ease-out ;
  -ms-transition: all .5s ease-out ;
  -o-transition: all .5s ease-out ;
  transition: all .5s ease-out ;
}
a:hover, a:active {
  box-shadow: 50px 7px 0 65px rgba(183, 118, 82, 0.9) inset;
  color: rgba(0, 0, 0, 1.0);
  text-shadow: 1px 1px 2px rgba(255, 255, 255, 1.0);
}

span {
  position: relative;
  top: 50%;
  font-size: 1.2em;
  margin-right: 13%;
}