Secouer sur une entrée invalide – 30 secondes de code

<input type="text" placeholder="Letters only" pattern="[A-Za-z]*" />

@keyframes shake {
  0% {
    margin-left: 0rem;
  }
  25% {
    margin-left: 0.5rem;
  }
  75% {
    margin-left: -0.5rem;
  }
  100% {
    margin-left: 0rem;
  }
}

input:invalid {
  animation: shake 0.2s ease-in-out 0s 2;
  box-shadow: 0 0 0.6rem #ff0000;
}