<a id="download-btn" class="download-float-btn" href="download_all.zip" download title="下载离线文档" style="visibility:hidden">
  <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M19 9h-4V3H9v6H5l7 7 7-7zM5 18v2h14v-2H5z"/></svg>
  <span>下载</span>
</a>