// ==UserScript==
// @name Autoscroll
// @namespace https://github.com/tokyo-jesus/
// @description Scrolls the page automatically
// @include http*://*
// @version 2.0.1
// @grant GM_registerMenuCommand
// ==/UserScript==

GM_registerMenuCommand("Autoscroll", function () {
  var speed = Number(prompt("Select speed (10 fast, 2000 slow; -1 to cancel)", "100"));
  var scroll = function () {
    if (speed > -1) {
      window.scrollBy(0 , 1);
      setTimeout(scroll, speed);
    }
  };
  setTimeout(scroll, speed);
});