wrangle body

javascript: (function() {
    if (document.getElementById('snippetSlider')) {
        return;
    }

    var body = document.querySelector("body");
    var slider = document.createElement("input");
    var styleTag = document.createElement("style");
    var styleString = "input[type=range]#snippetSlider{-webkit-appearance:none;margin:18px 0;width:200px}input[type=range]#snippetSlider:focus{outline:0}input[type=range]#snippetSlider::-webkit-slider-runnable-track{width:200px;height:8.4px;cursor:pointer;animate:.2s;box-shadow:1px 1px 1px #000,0 0 1px #0d0d0d;background:#3071a9;border-radius:1.3px;border:.2px solid #010101}input[type=range]#snippetSlider::-webkit-slider-thumb{box-shadow:1px 1px 1px #000,0 0 1px #0d0d0d;border:1px solid #000;height:36px;width:16px;border-radius:3px;background:#fff;cursor:pointer;-webkit-appearance:none;margin-top:-14px}input[type=range]#snippetSlider:focus::-webkit-slider-runnable-track{background:#367ebd}input[type=range]#snippetSlider::-moz-range-track{width:200px;height:8.4px;cursor:pointer;animate:.2s;box-shadow:1px 1px 1px #000,0 0 1px #0d0d0d;background:#3071a9;border-radius:1.3px;border:.2px solid #010101}input[type=range]#snippetSlider::-moz-range-thumb{box-shadow:1px 1px 1px #000,0 0 1px #0d0d0d;border:1px solid #000;height:36px;width:16px;border-radius:3px;background:#fff;cursor:pointer}input[type=range]#snippetSlider::-ms-track{width:200px;height:8.4px;cursor:pointer;animate:.2s;background:0 0;border-color:transparent;border-width:16px 0;color:transparent}input[type=range]#snippetSlider::-ms-fill-lower{background:#2a6495;border:.2px solid #010101;border-radius:2.6px;box-shadow:1px 1px 1px #000,0 0 1px #0d0d0d}input[type=range]#snippetSlider::-ms-fill-upper{background:#3071a9;border:.2px solid #010101;border-radius:2.6px;box-shadow:1px 1px 1px #000,0 0 1px #0d0d0d}input[type=range]#snippetSlider::-ms-thumb{box-shadow:1px 1px 1px #000,0 0 1px #0d0d0d;border:1px solid #000;height:36px;width:16px;border-radius:3px;background:#fff;cursor:pointer}input[type=range]#snippetSlider:focus::-ms-fill-lower{background:#3071a9}input[type=range]#snippetSlider:focus::-ms-fill-upper{background:#367ebd}";
    styleTag.innerHTML = styleString;
    slider.setAttribute("id", "snippetSlider");
    slider.setAttribute("type", "range");
    slider.setAttribute("min", "300");
    slider.setAttribute("max", "1000");
    slider.setAttribute("value", "800");
    slider.setAttribute("style", "position: fixed; top:0; right: 0");
    slider.addEventListener("input", function() {
        body.setAttribute("style", "margin: auto; max-width: " + slider.value + "px;")
    });
    body.appendChild(styleTag);
    body.appendChild(slider);
    body.setAttribute("style", "margin: auto; max-width: 800px;")
})()