diff --git a/engine/components/collide_rect.py b/engine/components/collide_rect.py
index 39a6133..adcd18a 100644
--- a/engine/components/collide_rect.py
+++ b/engine/components/collide_rect.py
@@ -12,13 +12,15 @@ class CollideRect(Component):
         self.vx = 0
         self.vy = 0
 
+    def x_change_cb(self, x):
+        self.rect.x = x
+
+    def y_change_cb(self, y):
+        self.rect.y = y
+
     def load(self):
-        def x_change_cb(x):
-            self.rect.x = x
-        def y_change_cb(y):
-            self.rect.y = y
-        self.parent.subscribe('x', x_change_cb)
-        self.parent.subscribe('y', y_change_cb)
+        self.parent.subscribe('x', self.x_change_cb)
+        self.parent.subscribe('y', self.y_change_cb)
 
     def register(self):
         PhysicsServer().register_component(self)
diff --git a/engine/entity.py b/engine/entity.py
index 3b6a1c8..551effe 100644
--- a/engine/entity.py
+++ b/engine/entity.py
@@ -1,5 +1,6 @@
 from .observer import Observer
 
+
 class Entity(Observer):
     def __init__(self, name):
         super().__init__()
diff --git a/engine/servers/input.py b/engine/servers/input.py
index 116df35..2cb54df 100644
--- a/engine/servers/input.py
+++ b/engine/servers/input.py
@@ -4,7 +4,8 @@ from pygame import event
 from pygame.locals import QUIT
 
 
-class StopException(RuntimeError): pass
+class StopException(RuntimeError):
+    pass
 
 
 class InputServer(Server):
diff --git a/engine/servers/server.py b/engine/servers/server.py
index ed0b856..8c3d046 100644
--- a/engine/servers/server.py
+++ b/engine/servers/server.py
@@ -14,7 +14,6 @@ class Server(metaclass=Singleton):
     def unregister_component(self, component):
         self._components.remove(component)
 
-
     @abstractmethod
     def step(self):
         pass
diff --git a/scenes/game_objects/ghost.py b/scenes/game_objects/ghost.py
index 6f923dc..0258a5c 100644
--- a/scenes/game_objects/ghost.py
+++ b/scenes/game_objects/ghost.py
@@ -1,6 +1,6 @@
 from random import random, randint
 
-from pygame import Surface, draw, Rect, image
+from pygame import Rect, image
 
 from engine.entity import Entity
 from engine.scene_manager import SceneManager
@@ -9,7 +9,6 @@ from engine.components.collide_rect import CollideRect
 from engine.components.sprite import Sprite
 
 from .common import S, Direction
-from .pacdot import PacDot
 
 
 class Ghost(Entity):
diff --git a/scenes/game_objects/level.py b/scenes/game_objects/level.py
index 826cc04..2704006 100644
--- a/scenes/game_objects/level.py
+++ b/scenes/game_objects/level.py
@@ -14,6 +14,7 @@ from .pacdot import PacDot, EnsmallmentDot
 
 class Node():
     cpt = 0
+
     def __init__(self):
         self.id = self.__class__.cpt
         self.__class__.cpt += 1
@@ -68,10 +69,10 @@ class Level(Entity):
                 if node is None:
                     continue
                 node.neighbors[Direction.LEFT.value] = \
-                    self.graph[y][(x-1)%w]
+                    self.graph[y][(x-1) % w]
                 node.neighbors[Direction.RIGHT.value] = \
-                    self.graph[y][(x+1)%w]
+                    self.graph[y][(x+1) % w]
                 node.neighbors[Direction.UP.value] = \
-                    self.graph[(y-1)%h][x]
+                    self.graph[(y-1) % h][x]
                 node.neighbors[Direction.DOWN.value] = \
-                    self.graph[(y+1)%h][x]
+                    self.graph[(y+1) % h][x]
diff --git a/scenes/main_menu.py b/scenes/main_menu.py
index afe6b75..e69de29 100644
--- a/scenes/main_menu.py
+++ b/scenes/main_menu.py
@@ -1,4 +0,0 @@
-class MainMenu(Scene):
-    pass
-
-scene = MainMenu()