.timeline{
  counter-reset: year 2018;
  position: relative;
}

.timeline li{
  list-style: none;
  float: left;
  width: 33.3333%;
  position: relative;
  text-align: center;
  text-transform: uppercase;
}

ul:nth-child(1){
  color: #4caf50;
}

.timeline li:before{
  counter-increment: year;
  content: counter(year);
  width: 50px;
  height: 50px;
  border: 3px solid #4caf50;
  border-radius: 50%;
  display: block;
  text-align: center;
  line-height: 50px;
  margin: 0 auto 10px auto;
  background: #F1F1F1;
  color: #000;
  transition: all ease-in-out .3s;
  cursor: pointer;
}

.timeline li:after{
  content: "";
  position: absolute;
  width: 100%;
  height: 1px;
  background-color: grey;
  top: 25px;
  left: -50%;
  z-index: -999;
  transition: all ease-in-out .3s;
}

.timeline li:first-child:after{
  content: none;
}
.timeline li.active{
  color: #555555;
}
.timeline li.active:before{
  background: #4caf50;
  color: #F1F1F1;
}

.timeline li.active + li:after{
  background: #4caf50;
}