State Transition

Handler.js

var W = World(function(transit){
  
  var Title;
  var Game;
  
  Title = function(){
    var h = {};
    var x = 0;
    Input.listen(function(c){
      if(c == Key.Enter)transit(Game(x));
    });
    h.step = function(){
      x++;
    };
    h.draw = function(){
      Graphics.drawCircle(x,height/2,0xff0000);
    };
    return h;
  };
  
  Game = function(ini){return function(){
    var h = {};
    var x = ini;
    Input.listen(function(c){
      if(c == Key.Escape)transit(Title);
    });
    h.step = function(){
      x--;
    };
    h.draw = function(){
      Graphics.drawCircle(x,height/2,0xffff00);
    };
    return h;
  };};
  
  return Title;
    
});

World.js

World = function(init){
  var w = {};
  w.current = null;
  function transit(h){
    w.current = h();
    Screen.step(function(){
      w.current.step();
      w.current.draw();
    });
  }
  transit(init(transit));
  return w;
};