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

@keyframes shake {
    0% { transform: rotate(0deg); }
    20% { transform: rotate(-15deg); }
    40% { transform: rotate(15deg); }
    60% { transform: rotate(-10deg); }
    80% { transform: rotate(10deg); }
    100% { transform: rotate(0deg); }
}