@keyframes shake {
    0% { transform: rotate(0deg); }
    25% { transform: rotate(10deg); }
    50% { transform: rotate(0deg); }
    75% { transform: rotate(-10deg); }
    100% { transform: rotate(0deg); }
  }
  
  #result.shake {
    animation: shake 0.5s ease-in-out infinite;
  }