diff --git a/main.py b/main.py
index a75e9ba..f4fb648 100644
--- a/main.py
+++ b/main.py
@@ -1,8 +1,14 @@
 import pygame as pg
-from source.main import main
+from source import tool
+from source import constants as c
+from source.state import mainmenu, screen, level
 
 if __name__=='__main__':
-    # do everything in this main function
-    main()
-    # don't forget quit for release all resource
-    pg.quit()
\ No newline at end of file
+    # 控制状态机运行
+    game = tool.Control()
+    state_dict = {c.MAIN_MENU: mainmenu.Menu(),
+                  c.GAME_VICTORY: screen.GameVictoryScreen(),
+                  c.GAME_LOSE: screen.GameLoseScreen(),
+                  c.LEVEL: level.Level()}
+    game.setup_states(state_dict, c.MAIN_MENU)
+    game.run()
\ No newline at end of file
diff --git a/resources/graphics/Screen/exit.png b/resources/graphics/Screen/exit.png
new file mode 100644
index 0000000..2a9e218
Binary files /dev/null and b/resources/graphics/Screen/exit.png differ
diff --git a/source/constants.py b/source/constants.py
index 09bfc9c..76fccba 100644
--- a/source/constants.py
+++ b/source/constants.py
@@ -24,6 +24,12 @@ GREEN        = (  0, 255,   0)
 
 SIZE_MULTIPLIER = 1.3
 
+# 退出游戏按钮
+EXIT = 'exit'
+# 当想要一个特殊值时用
+NULL = 'null'
+
+
 #GAME INFO DICTIONARY KEYS
 CURRENT_TIME = 'current time'
 LEVEL_NUM = 'level num'
diff --git a/source/main.py b/source/main.py
deleted file mode 100644
index b1badeb..0000000
--- a/source/main.py
+++ /dev/null
@@ -1,16 +0,0 @@
-__author__ = 'wcb'
-
-from . import tool
-from . import constants as c
-from .state import mainmenu, screen, level
-
-# create a standard game
-def main():
-    # 控制状态机运行
-    game = tool.Control()
-    state_dict = {c.MAIN_MENU: mainmenu.Menu(),
-                  c.GAME_VICTORY: screen.GameVictoryScreen(),
-                  c.GAME_LOSE: screen.GameLoseScreen(),
-                  c.LEVEL: level.Level()}
-    game.setup_states(state_dict, c.MAIN_MENU)
-    game.run()
\ No newline at end of file
diff --git a/source/state/mainmenu.py b/source/state/mainmenu.py
index 168af18..4f17dc8 100644
--- a/source/state/mainmenu.py
+++ b/source/state/mainmenu.py
@@ -1,8 +1,10 @@
 import pygame as pg
 from .. import tool
 from .. import constants as c
+from . import level
 
 class Menu(tool.State):
+    
     def __init__(self):
         tool.State.__init__(self)
     
@@ -10,7 +12,6 @@ class Menu(tool.State):
         self.next = c.LEVEL
         self.persist = persist
         self.game_info = persist
-        
         self.setupBackground()
         self.setupOption()
 
@@ -38,6 +39,13 @@ class Menu(tool.State):
         self.option_rect.x = 435
         self.option_rect.y = 75
         
+        # 退出按钮
+        frame_rect = [0, 0, 500, 500]
+        self.option_exit = tool.get_image_menu(tool.GFX[c.EXIT], *frame_rect, c.BLACK, 1.1)
+        self.exit_rect = self.option_exit.get_rect()
+        self.exit_rect.x = 690
+        self.exit_rect.y = 400
+
         self.option_start = 0
         self.option_timer = 0
         self.option_clicked = False
@@ -49,7 +57,15 @@ class Menu(tool.State):
             self.option_clicked = True
             self.option_timer = self.option_start = self.current_time
         return False
-        
+    
+    # 点击到按钮，修改转态的done属性
+    def checkExitClick(self, mouse_pos):
+        x, y = mouse_pos
+        if(x >= self.exit_rect.x and x <= self.exit_rect.right and
+           y >= self.exit_rect.y and y <= self.exit_rect.bottom):
+            self.done = True
+            self.next = c.EXIT
+
     def update(self, surface, current_time, mouse_pos, mouse_click):
         self.current_time = self.game_info[c.CURRENT_TIME] = current_time
         
@@ -57,6 +73,7 @@ class Menu(tool.State):
         if not self.option_clicked:
             if mouse_pos:
                 self.checkOptionClick(mouse_pos)
+                self.checkExitClick(mouse_pos)
         else:
             # 点到后播放动画
             if(self.current_time - self.option_timer) > 200:
@@ -67,6 +84,8 @@ class Menu(tool.State):
                 self.option_image = self.option_frames[self.option_frame_index]
             if(self.current_time - self.option_start) > 1300:
                 self.done = True
+                
 
         surface.blit(self.bg_image, self.bg_rect)
-        surface.blit(self.option_image, self.option_rect)
\ No newline at end of file
+        surface.blit(self.option_image, self.option_rect)
+        surface.blit(self.option_exit, self.exit_rect)
\ No newline at end of file
diff --git a/source/tool.py b/source/tool.py
index ed5aa53..b34ec32 100644
--- a/source/tool.py
+++ b/source/tool.py
@@ -64,6 +64,9 @@ class Control():
 
     # 状态转移
     def flip_state(self):
+        if self.state.next == c.EXIT:
+            pg.quit()
+            os._exit(0)
         previous, self.state_name = self.state_name, self.state.next
         persist = self.state.cleanup()
         self.state = self.state_dict[self.state_name]
@@ -98,7 +101,8 @@ def get_image(sheet, x, y, width, height, colorkey=c.BLACK, scale=1):
         rect = image.get_rect()
 
         image.blit(sheet, (0, 0), (x, y, width, height))
-        image.set_colorkey(colorkey)
+        if colorkey != c.NULL:
+            image.set_colorkey(colorkey)
         image = pg.transform.scale(image,
                                    (int(rect.width*scale),
                                     int(rect.height*scale)))