A very polished game that is a lot of fun! I would recommend having the gun fire automatically while holding down fire but more importantly making the game webgl (playable in browser) because that is what is limiting people from trying and rating your game, it should be pretty simple and there are a lot of tutorials on YouTube. If it was in browser instead of downloading for windows or mac, I'm sure many more people would be playing this!
Edit: Highest I got to was 24