save project

snake.py

@@ -59,7 +59,8 @@ while True:
         ay = random.randint(0,15)*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))
     # 将贪吃蛇的头画上去