// Class.extend takes a function that returns the options object
//     it is passed the accessor function generated in the Pvt.js example above
var Person = Class.extend(function(pvt) {

  // private static member
  var species = "Homo sapien";

  return {
    init: function(isDancing) {
      // pvt(this).invisible === undefined
      // pvt(this).hasSword === undefined

      pvt(this).dancing = isDancing;
      // pvt(this).dancing === isDancing
    },
    dance: function() {
      return pvt(this).dancing;
    },
    getSpecies: function() {
      return species ;
    }
  };
});

var Ninja = Person.extend(function(pvt) {
  return {
    init: function(hasSword){
      pvt(this).invisible = true;
      this._super( false );
      pvt(this).hasSword = hasSword || true;

      // pvt(this).dancing === false
    },
    dance: function(){
      // Call the inherited version of dance()
      return this._super();
    },
    swingSword: function(){
      return pvt(this).hasSword;
    }
  };
});


var p = new Person(true);
p.dance(); // => true

var n = new Ninja();
n.dance(); // => false
n.swingSword(); // => true

// Should all be true
p instanceof Person && p instanceof Class &&
  n instanceof Ninja && n instanceof Person && n instanceof Class;