.shake:hover {
  animation: shake 0.5s ease-in-out infinite;
}

@keyframes shake {
  0%   { transform: rotate(0deg); }
  20%  { transform: rotate(10deg); }
  40%  { transform: rotate(-10deg); }
  60%  { transform: rotate(8deg); }
  80%  { transform: rotate(-8deg); }
  100% { transform: rotate(0deg); }
}