I have to ask, was this made in Scratch? If so, that's really cool. I didn't even know you could export a game in Scratch lol.
A small suggestion would be to make the enemies give at least one bullet after they're killed. The fact that there's less than one means that the player is guaranteed to run out eventually and then the game is pretty much over. I think it'd be cool to see an endless mode where if you run out of bullets you lose.
Pretty cool game! Awesome job!