auto save

snake.py

@@ -58,7 +58,9 @@ while True:
     if x == apple_x and y == apple_y:
         apple_x = random.randint(0,660)    
         apple_y = random.randint(0,480)    
-   
+    else:
+        pisition.pop(0)
+
     position.pop(0)
     # 将背景图画上去
     screen.blit(background, (0, 0))