.btn{
  display: inline-block;
  width: 60px;border-radius:5px;
  height: 35px;
  background: #fff;
  margin-top: 0px;cursor: pointer;
  
  box-shadow: 0 5px 15px -5px #00000070;
  color: #111;
  overflow: hidden;
  position: relative;
}
.btn i{
  line-height: 0px;
  font-size: 20px;
  transition: 0.2s linear;
}
.btn:hover i{
  transform: scale(1.0);
  color: #fff;
}
.btn::before{
  content: "";
  position: absolute;color:black;
  width: 120%;
  height: 120%;
  background: green;
  transform: rotate(45deg);
  left: -110%;
  top: 90%;
}
.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%;
  }
}
button:hover{
        box-shadow: 5px 15px 30px rgba(0, 0, 0, 0.6);
}