save project

snake.py

@@ -52,6 +52,8 @@ while True:
         y -= 30
     else:
         y += 30
+
+    if x < 0 or y < 0 or x >630 or y >450:
     position.append((x, y))
     # 将背景图画上去.
     screen.blit(background, (0, 0))