thanks for feed back, i will add at description how to use stair, and for saving i just used PlayerPrefs, the browser have the ability to save it as any device as they not more than 20 Mb , and of course they are less than 1, then i delete them all when game over, to make user start from beginning.
by the way when you advance on the levels you can use cookies to bye ammo or shield from the shop at start scene or from any level from the shop at pause menu