auto save

snake.py

@@ -60,8 +60,10 @@ while True:
         num2=random.randint(0,16)
         apple_x=num1*30-30
         apple_y=num2*30-30
-    else：
+    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