--- a07/jogo.py	2005-10-08 12:24:11.000000000 -0300
+++ a08/jogo.py	2005-10-08 13:38:36.000000000 -0300
@@ -4,7 +4,7 @@
 ###############################################################################
 #
 # Mudanças em relação à versão anterior:
-#    - otimizações: usar colorkey ao invés de transparência por pixel (alpha)
+#    - otimizações: usar técnica de "dirty-rectangles"
 #
 ###############################################################################
 
@@ -346,6 +346,8 @@
             self.bgcolor = pygame.color.Color( bgcolor )
         self.pos     = pos or [ 0, 0 ]
         self.font    = pygame.font.Font( font, ptsize )
+
+        self.last_rect = None
     # __init__()
 
     def update( self, dt ):
@@ -353,21 +355,26 @@
     # update()
 
     def draw( self, screen ):
-        xp = self.player.get_XP()
-        if self.last_xp != xp:
-            self.last_xp = xp
-            text = "XP: % 4d" % xp
-            if self.bgcolor:
-                self.image = self.font.render( text, False, self.fgcolor,
-                                               self.bgcolor )
-            else:
-                self.image = self.font.render( text, False, self.fgcolor,
-                                               ( 255, 0, 255 ) )
-                self.image.set_colorkey( ( 255, 0, 255 ), RLEACCEL )
-                
+        text = "XP: % 4d" % self.player.get_XP()
+        if self.bgcolor:
+            self.image = self.font.render( text, False, self.fgcolor,
+                                           self.bgcolor )
+        else:
+            self.image = self.font.render( text, False, self.fgcolor,
+                                           ( 255, 0, 255 ) )
+            self.image.set_colorkey( ( 255, 0, 255 ), RLEACCEL )
+
+        self.last_rect = Rect( self.pos, self.image.get_size() )
+
         screen.blit( self.image, self.pos )
             
     # draw()
+
+
+    def clear( self, screen, background ):
+        if self.last_rect:
+            screen.blit( background, self.last_rect )
+    # clear()
 # PlayerXPStatus
 
 
@@ -391,6 +398,7 @@
         self.player     = player
         self.pos        = pos or [ 5, 5 ]
         self.size_image = self.image.get_size()
+        self.last_rect  = None
     # __init__()
 
 
@@ -406,7 +414,16 @@
         for i in range( self.player.get_lives() ):
             pos[ 0 ] += self.size_image[ 0 ] + self.spacing
             screen.blit( self.image, pos )
+
+        pos[ 1 ] = self.size_image[ 1 ]
+        self.last_rect = Rect( self.pos, pos )
     # draw()
+
+
+    def clear( self, screen, background ):
+        if self.last_rect:
+            screen.blit( background, self.last_rect )
+    # clear()
 # PlayerLifeStatus
 
 
@@ -421,7 +438,9 @@
     """
     image = None
     pos   = None
-    
+    update_threshold = 30
+    update_step      = 1
+
     def __init__( self, image="tile.png" ):
         """
         Com essa função criamos uma superfície, formada de uma repetição da
@@ -455,7 +474,7 @@
             image = image.convert()
 
 	self.isize = image.get_size()
-	self.pos = [ 0, -1 * self.isize[ 1 ] ]
+	self.pos = [ 0, 0 ]
         screen      = pygame.display.get_surface()
         screen_size = screen.get_size()
 
@@ -473,20 +492,35 @@
 
         back.set_alpha( None, RLEACCEL )
         self.image = back.convert()
+
+        self.last = 0
+        self.current = self.update_threshold # atualize na primeira vez
     # __init__()
 
 
 
     def update( self, dt ):
-        self.pos[ 1 ] += 1
-        if ( self.pos[ 1 ] > 0 ):
-            self.pos[ 1 ] -= self.isize[ 1 ]
+        self.current += 1
     # update()
 
 
 
     def draw( self, screen ):
-        screen.blit( self.image, self.pos )
+        size = screen.get_size()
+
+        if self.current >= self.last + self.update_threshold:
+            self.last = self.current
+            self.pos[ 1 ] += self.update_step
+
+            current_rect = Rect( self.pos, size )
+            image_rect   = self.image.get_rect()
+
+            if not image_rect.contains( current_rect ):
+                self.pos[ 1 ] -= self.isize[ 1 ]
+
+            screen.blit( self.image, self.pos )
+
+        return self.image.subsurface( Rect( self.pos, size ) )
     # draw()
 # Background
 
@@ -607,10 +641,18 @@
     # actors_update()
 
 
+    def actors_clear( self ):
+        bg = self.background.draw( self.screen )
+
+        for actor in self.list.values():
+            actor.clear( self.screen, bg )
+
+        self.player_life.clear( self.screen, bg )
+        self.player_xp.clear( self.screen, bg )
+    # actors_clear()
+
 
     def actors_draw( self ):
-        self.background.draw( self.screen )
-        
         for actor in self.list.values():
             actor.draw( self.screen )
             
@@ -621,7 +663,7 @@
 
 
     def actor_check_hit( self, actor, list, action ):
-        if   isinstance( actor, pygame.sprite.RenderPlain ):
+        if   isinstance( actor, pygame.sprite.RenderUpdates ):
             hitted = pygame.sprite.groupcollide( actor, list, 1, 0 )
             for v in hitted.values():
                 for o in v:
@@ -729,11 +771,11 @@
                                            fgcolor="0xff0000" )
 
         self.list = {
-            "player"       : pygame.sprite.RenderPlain( self.player ),
-            "enemies"      : pygame.sprite.RenderPlain( Enemy( [ 120, 0 ],
+            "player"       : pygame.sprite.RenderUpdates( self.player ),
+            "enemies"      : pygame.sprite.RenderUpdates( Enemy( [ 120, 0 ],
                                                                image=self.image_enemy ) ),
-            "fire"         : pygame.sprite.RenderPlain(),
-            "enemies_fire" : pygame.sprite.RenderPlain()
+            "fire"         : pygame.sprite.RenderUpdates(),
+            "enemies_fire" : pygame.sprite.RenderUpdates()
             }
 
         # assim iniciamos o loop principal do programa
@@ -752,7 +794,10 @@
 
             # Faça a manutenção do jogo, como criar inimigos, etc.
             self.manage()
-            
+
+            # Limpe o que os atroes sujaram durante a iteração anterior
+            self.actors_clear()
+
             # Desenhe para o back buffer
             self.actors_draw()