+class WorldEvent(Event):
+ """ Be a hero. Change the world. """
+
+ ENGINE_METHOD = "change_world"
+
+
+class QuitEvent(Event):
+ """ Quit the game. """
+
+ ENGINE_METHOD = "quit_game"
+
+
+class MoveViewportEvent(Event):
+ """ Change to a new scene. """
+
+ ENGINE_METHOD = "move_screen"
+
+
+class Actors:
+ """ A list of actors. """
+
+ def __init__(self):
+ self._actors = []
+
+ def add(self, actor):
+ self._actors.append(actor)
+ return actor
+
+ def remove(self, actor):
+ self._actors.remove(actor)
+ return actor
+
+ def draw(self, screen):
+ for actor in self._actors:
+ actor.draw() # TODO: allow an option screen to be passed in
+
+