index.html

<style>
/**
 * GitHub Corners, page css
 * Author: Tim Holman
 */
.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;
    }
}
</style>
<div id="root"></div>
<a class="github-corner" href="https://github.com/djblue/sudoku">
  <svg xmlns="http://www.w3.org/2000/svg" width="80" height="80" viewBox="0 0 250 250" fill="#1c1c1e" style="position: absolute; top: 0; right: 0">
    <path d="M0 0l115 115h15l12 27 108 108V0z" fill="#1083ac"/>
    <path class="octo-arm" d="M128 109c-15-9-9-19-9-19 3-7 2-11 2-11-1-7 3-2 3-2 4 5 2 11 2 11-3 10 5 15 9 16" style="-webkit-transform-origin: 130px 106px; transform-origin: 130px 106px"/>
    <path class="octo-body" d="M115 115s4 2 5 0l14-14c3-2 6-3 8-3-8-11-15-24 2-41 5-5 10-7 16-7 1-2 3-7 12-11 0 0 5 3 7 16 4 2 8 5 12 9s7 8 9 12c14 3 17 7 17 7-4 8-9 11-11 11 0 6-2 11-7 16-16 16-30 10-41 2 0 3-1 7-5 11l-12 11c-1 1 1 5 1 5z"/>
  </svg>
</a>
<script src="main.js"></script>