--- a/skaapsteker/physics.py	Mon Apr 04 21:45:59 2011 +0200
+++ b/skaapsteker/physics.py	Mon Apr 04 21:54:42 2011 +0200
@@ -27,6 +27,9 @@
     collision_layer = None # never collides with anything
     collides_with = set() # nothing collides with this
 
+    # set to True to have .update() called once per tick
+    wants_updates = False
+
     def __init__(self, *args, **kwargs):
         super(Sprite, self).__init__(*args, **kwargs)
         self.velocity = (0.0, 0.0)
@@ -81,6 +84,9 @@
         v_y = (1.0 - normal[1] * b_y) * v_y
         self.velocity = v_x, v_y
 
+    def update(self):
+        pass # only called in wants_update = True
+
 
 class World(object):
 
@@ -90,6 +96,7 @@
         self._all = pygame.sprite.LayeredUpdates()
         self._mobiles = pygame.sprite.Group()
         self._gravitators = pygame.sprite.Group()
+        self._updaters = pygame.sprite.Group()
         self._collision_groups = { None: pygame.sprite.Group() }
         self._last_time = None
 
@@ -106,6 +113,8 @@
             self._mobiles.add(sprite)
         if sprite.gravitates:
             self._gravitators.add(sprite)
+        if sprite.wants_updates:
+            self._updaters.add(sprite)
         self._add_collision_group(sprite.collision_layer)
         for layer in sprite.collides_with:
             self._add_collision_group(layer)
@@ -163,6 +172,9 @@
             if collisions:
                 self._backout_collisions(sprite, collisions, dt)
 
+        # call update methods
+        self._updaters.update()
+
     def draw(self, surface):
         self._all.draw(surface)
         if options['debug_rects']:

--- a/skaapsteker/sprites/player.py	Mon Apr 04 21:45:59 2011 +0200
+++ b/skaapsteker/sprites/player.py	Mon Apr 04 21:54:42 2011 +0200
@@ -13,6 +13,7 @@
 
     collision_layer = PC_LAYER
     collides_with = set([MONSTER_LAYER])
+    wants_updates = True
 
     def __init__(self):
         Sprite.__init__(self)
@@ -35,6 +36,9 @@
         # TODO: handle animations
         self.image = self._image_dict[key][0]
 
+    def update(self):
+        pass # animate tail here
+
     def set_facing(self, new_facing):
         self.facing = new_facing