Kilometrówka V2

(function (_, k, m, __) {
    function km(n) {
        return (n / 9600000 * 2.54).toFixed(4) + ` km`;
    }
    var pX = 0;
    var pY = 0;
    var ch = new BroadcastChannel(m);
    var c = parseInt(localStorage[m], 10) || 0;
    var x = c;
    __ = _.createElement(`li`);
    __.innerHTML = `Kilometrówka: <span style="font-weight: bold">${km(c)}</span>`;
    _.querySelector("ul.rules").appendChild(__);
    __ = __.childNodes[1];
    ch.onmessage = function(e) {
        if (c > e.data) {
            ch.postMessage(c);
            return;
        }
        c = e.data;
        __.innerHTML = km(c);
    };
    _.onmousemove = function(e) {
        c += k.sqrt(k.pow(pX - e.screenX, 2) + k.pow(pY - e.screenY, 2));
        pX = e.screenX;
        pY = e.screenY;
        __.innerHTML = km(c);
        ch.postMessage(c);
    };
    _.body.onbeforeunload = function() {
        localStorage[m] = c;
    };
})(document, Math, "kilometrowka");