save project

snake.py

@@ -62,6 +62,9 @@ while True:
         apple_y=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