ll(":is(a, button)");
    for (const el of tabbable) {
        el.tabIndex = tabIndex++;
    }

    append(document.body, dfnPanel);
    positionDfnPanel(dfnPanel);
}

function positionDfnPanel(dfnPanel) {
    const dfn = dfnPanel.dfn;
    const dfnPos = getBounds(dfn);
    dfnPanel.style.top = dfnPos.bottom + "px";
    dfnPanel.style.left = dfnPos.left + "px";

    const panelPos = dfnPanel.getBoundingClientRect();
    const panelMargin = 8;
    const maxRight = document.body.parentNode.clientWidth - panel