button {
  width: 100px;
  height: 50px;
  border-radius: 30em;
  font-size: 15px;
  font-family: inherit;
  border: none;
  position: relative;
  overflow: hidden;
  z-index: 1;
  box-shadow: 6px 6px 12px #c5c5c5,
             -6px -6px 12px #ffffff;
}

button:hover {
  color: #ffffff;
  transform: scale(1.1);
  outline: 2px solid #70bdca;
  box-shadow: 4px 5px 17px -4px #268391;
}

button::before {
  content: "";
  position: absolute;
  left: -50px;
  top: 0;
  width: 0;
  height: 100%;
  background-color: #2c9caf;
  transform: skewX(45deg);
  z-index: -1;
  transition: width 1000ms;
}

button:hover::before {
  width: 250%;
}