.box {
  position:relative;
  vertical-align: middle;
  color: rgba(51,204,51,1);
  font-family: 'Nunito', sans-serif;
  display: inline-block;
  height: 60px;
  line-height: 60px;
  text-align: center;
  transition: 0.5s;
  padding: 0 20px;
  cursor: pointer;
  border: 2px solid rgba(51,204,51,1);
  -webkit-transition:0.5s;
}

.box:hover {
  border: 2px solid rgba(0,160,80,0);
  color: #000;
}

.box::before, .box::after {
  width: 100%;
  height:100%;
  z-index: 3;
  content:'';
  position: absolute;
  top:0;
  left:0;
  box-sizing: border-box;
  -webkit-transform: scale(0);
  transition: 0.5s;
}

.foo::before {
  border-bottom: 3px solid #000;
  border-left: 3px solid #000;
  -webkit-transform-origin: 0 100%;
}

.foo::after {
  border-top: 3px solid #000;
  border-right: 3px solid #000;
  -webkit-transform-origin: 100% 0%;
}


.bar::before {
  border-bottom: 3px solid #000;
  border-left: 3px solid #000;
  -webkit-transform-origin: 100% 0%;
}

.bar::after {
  border-top: 3px solid #000;
  border-right: 3px solid #000;
  -webkit-transform-origin: 0% 100%;
}

.curmudgeon::before {
  border-bottom: 3px solid #000;
  border-left: 0;
  -webkit-transform-origin: 0% 100%;
}

.curmudgeon::after {
  border-top: 0;
  border-right: 0;
  -webkit-transform-origin: 50% 50%;
}

.box:hover::after, .box:hover::before {
  -webkit-transform: scale(1);
}

.link {
  line-height: 1em;
  position: absolute;
  bottom: 0;
  right: 20px;
  width: 300px;
  height: 50px;
 font-family: 'Nunito', sans-serif;
  text-align: right; 
}

.link > a {
  text-decoration: none;
  color: #FF0;
}