.btn {
  position: relative;
  background: none;
  border: 2px solid black;
  font-size: 1.2rem;
  padding: 1rem 2rem;
  border-radius: 0.5rem;
  transition: all 0.3s;
}
.btn::before {
  content: "";
  height: 0%;
  width: 0%;
  border-radius: 50%;
  top: 50%;
  left: 50%;
  z-index: -1;
  position: absolute;
  background-color: #494958;
  transition: all 0.3s;
}
.btn:hover {
  border: 2px solid #32323c;
  color: white;
}
.btn:hover::before {
  top: 0;
  left: 0;
  height: 100%;
  width: 100%;
  border-radius: 0.3rem;
}