.btn {
  display: flex;
  justify-content: center;
  align-items: center;
  color: #ffffff;
  outline: none;
  height: 50px;
  width: 150px;
  border: none;
  text-decoration: none;
  background-image: linear-gradient(115deg,#4fcf70,#fad648,#a767e5,#12bcfe,#44ce7b);
}

.btn:hover {
  animation: rotate 0.4s linear infinite;
}

@keyframes rotate {
  100% {
    filter: hue-rotate(-360deg)
  }
}

.btn span {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 42px;
  width: 142px;
  background: #222222;
  font-size: 18px;
}