save project

snake.py

@@ -53,6 +53,7 @@ while True:
         apple_y= 30*num2-30
     else:
         position.pop(0)
+    if x < 0 or x > 630 or y > 450:
     # 将背景图画上去
     screen.blit(background, (0, 0))
     # 将贪吃蛇画上去