That was quite fun! It nees some work on a few things like more art for environment/level desing, but I think it's a good prototype.
I didn't mind having to go back to switch between weapons, though it would be nice if you explained that at the start. But I thought it was fun trying to run back & forth all the time. Could be even more fun in more complex levels! :D I only wish it had some music and SFX :-)
All in all, fun idea and nice touch at the end with the extra message!