second.css

.github-corner:hover .octo-arm {
    animation: octocat-wave 560ms ease-in-out;
}

@keyframes octocat-wave {
    0% {
        transform: rotate(0deg);
    }

    20% {
        transform: rotate(-25deg);
    }

    40% {
        transform: rotate(10deg);
    }

    60% {
        transform: rotate(-25deg);
    }

    80% {
        transform: rotate(10deg);
    }

    100% {
        transform: rotate(0deg);
    }
}

@media (max-width: 500px) {
    .github-corner:hover .octo-arm {
        animation: none;
    }

    .github-corner .octo-arm {
        animation: octocat-wave 560ms ease-in-out;
    }
}