@keyframes left-side-btn{
  20%{left: -90px;}
  40%{left: -85px;}
  60%{left: -80px;}
  80%{left: -75px;}
}
@keyframes right-side-btn{
  20%{right: -90px;}
  40%{right: -85px;}
  60%{right: -80px;}
  80%{right: -75px;}
}
@-webkit-keyframes right-side-btn{
  20%{left: -90px;}
  40%{left: -85px;}
  60%{left: -80px;}
  80%{left: -75px;}
}
@-webkit-keyframes right-side-btn{
  20%{right: -90px;}
  40%{right: -85px;}
  60%{right: -80px;}
  80%{right: -75px;}
}

.side-btn{
  font-family: sans-serif;
  position: fixed;
  width: 220px;
  height: 80px;
  top: 45%;
  border-top-left-radius: 10px;
  border-top-right-radius: 10px;
  background: #d45;
  text-align: center;
  transition: 0.3s ease;
  animation-name: side-btn;
  animation-duration: 1.5s;
  animation-iteration-count: infinite;
  -webkit-animation-duration: 1.5s;
  -webkit-animation-iteration-count: infinite;
  z-index: 100;
}

.side-btn a{
  display: block;
  width: 100%;
  height: 100%;
  line-height: 70px;
  font-size: 18px;
  color: #fff;
  text-decoration: none;
  border-top-left-radius: 10px;
  border-top-right-radius: 10px;
}

.left-side-btn{
  left: -90px;
  -ms-transform: rotate(90deg);
  -moz-transform: rotate(90deg);
  -webkit-transform: rotate(90deg);
  -o-transform: rotate(90deg);
  -webkit-animation-name: left-side-btn;
}

.right-side-btn{
  right: -90px;
  width: 220px;
  height: 80px;
  -ms-transform: rotate(270deg);
  -moz-transform: rotate(270deg);
  -webkit-transform: rotate(270deg);
  -o-transform: rotate(270deg);
  -webkit-animation-name: right-side-btn;
}

.side-btn:hover{
  transition: 0.9s ease;
  right: -75px;
  top: 45%;
  width: 240px;
  height: 100px;
  -ms-animation-play-state: paused;
  -moz-animation-play-state: paused;
  -webkit-animation-play-state: paused;
  -o-animation-play-state: paused;
}