save project

snake.py

 import pygame
-from pygame import locals
 import random
+from pygame import locals
 
 # 初始化pygame，为使用硬件做准备
 pygame.init()
@@ -63,7 +63,8 @@ while True:
         apple_y = num2 * 30 - 30
     else:
         position.pop(0)
-        
+    if x < 0 or x > 630 or y < 0 or y >450:
+        exit()
 
     # 将背景图画上去
     screen.blit(background, (0, 0))
@@ -76,4 +77,6 @@ while True:
     # 将果实画上去
     screen.blit(food, (apple_x, apple_y))
     # 刷新画面
+    pygame.display.update()
+    FPSCLOCK.tick(3)
     
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