buttom.css

.buttom
{
  position: absolute;
  top: 10%;
  transform: translateY(-50%);
  width: 100%;
  text-align: center;
}
.btn
{
  display: inline-block;
  width: 90px;
  height: 90px;
  background: #f1f1f1;
  margin: 10px;
  border-radius: 30%;
  box-shadow: 0 5px 15px -5px #00000070;
  color: (45deg,#036eb7,#64eaff);
  overflow: hidden;
  position: relative;
}
.btn i
{
  line-height: 90px;
  font-size: 12px;
  transition: 0.2s linear;
}
.btn:hover i
{
  transform: scale(1.3);
  color: #f1f1f1;
}
.btn:before
{
  content: "";
  position: absolute;
  width: 120%;
  height: 120%;
  background: #3498db;
  transform: rotate(45deg);
  left: -110%;
  top: 80%;
}
.btn:hover:before
{
  animation: aaa 0.7s 1;
  top: -10%;
  left: -10%;
}
@keyframes aaa
{
  0%{
    left: -110%;
    top: 90%;
  }50%{
    left: 10%;
    top: -30%;
  }100%{
    top: -10%;
    left: -10%;
  }
}