.btn {
  display: inline-block;
  font-family: sans-serif;
  font-weight: 600;
  font-size: 16px;
  color: #fff;
  margin: 1rem auto;
  padding: 0.7rem 2rem;
  border-radius: 30em;
  border-style: none;
  position: relative;
  z-index: 1;
  overflow: hidden;
  text-decoration: none;
  text-transform: uppercase;
  letter-spacing: 2px;
  background-color: transparent;
  box-shadow: 1px 1px 12px #000000;
}

.btn::before {
  content: "";
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
  background-color: #fff;
  transform: translateX(-101%);
  transition: all .3s ease;
  z-index: -1;
}

.btn:hover {
  color: #272727;
  transition: all .3s ease;
}

.btn:hover::before {
  transform: translateX(0);
}