@keyframes shake {
    0% {
        transform: rotate(0);
    }
    25% {
        transform: rotate(-5deg);
    }
    50% {
        transform: rotate(5deg);
    }
    75% {
        transform: rotate(-5deg);
    }
    100% {
        transform: rotate(0);
    }
}


.navbar-brand > img {
    max-height: 60px;
}

i.border-circle {
    border-radius: 50%;
    border: 5px solid #666666;
    width: 2em;
    height: 2em;
    display: flex;
    justify-content: center;
    align-items: center;
    margin: auto;
    transition: ease-in-out 0.2s all;
}

a:hover i.border-circle {
   filter: drop-shadow(1px 1px 3px rgba(0, 0, 0, 0.15));
   animation: shake 0.5s infinite;
}