save project

snake.py

@@ -60,6 +60,8 @@ while True:
         apple_y = num2*30-30
     else:
         position.pop(0)
+    if x < 0 or x > 630 or y < 0 or y > 450
+    
     # 将背景图画上去
     screen.blit(background, (0, 0))
     # 将贪吃蛇的头画上去