// See http://www.kevlindev.com/tutorials/javascript/inheritance/index.htm
// for information about how great this class-style of inheritance
// is in JavaScript.

function extend(subclass, superclass) {
  function Dummy(){}
  Dummy.prototype = superclass.prototype;
  subclass.prototype = new Dummy();
  subclass.prototype.constructor = subclass;
  subclass.superclass = superclass;
  subclass.superproto = superclass.prototype;
};