save project

snake.py

@@ -64,6 +64,8 @@ while True:
         score+=1
     else:
         position.pop(0)
+    if x<0 or x>660 or y<0 or y>480:
+        exit()
     # 将背景图画上去
     screen.blit(background, (0, 0))
     # 将贪吃蛇的头画上去