document.addEventListener("DOMContentLoaded", function () {
    // subtitles
    var b = document.createElement("button"),
        c = document.createElement("div");
    c.appendChild(b);
    b.innerHTML = "toggle";
    b.addEventListener("click", function () {
        document.body.classList.toggle("subtitle");
    });

    document.body.append(c);
    c.id = "controls";

    
})