#password-rules i, #password-rules svg {
    transition: color .25s ease, fill .25s ease, transform .25s ease;
}

.shake { animation: shake .35s; }
@keyframes shake {
  10%, 90% { transform: translateX(-1px); }
  20%, 80% { transform: translateX(2px); }
  30%, 50%, 70% { transform: translateX(-4px); }
  40%, 60% { transform: translateX(4px); }
}

button[disabled] {
    opacity: .6;
    cursor: not-allowed;
    filter: grayscale(40%);
}