Is this your first game? Congrats! It's a really nice and complete submission!
Some thoughts:
1) Make the SFX volume consistent with the music volume (the "machine gun" sounds way too loud hah)
2) You should try to avoid spawning enemies too close to the player
3) Enemies shouldn't shoot you if they are not on screen
Viewing post in The Good Alien jam comments
Hahahahah the machine gun is too loud indeed hahahah I have to change that. Yes, it is my first game. It took more time than I imagined. Making games is not that easy! haha I will change those things in the next updates, thanks for the tips and feedback! I've played your game too, it was different from the others I've played, love it! I would suggest something like a "roadmap" indicating how many waves are left until the boss or something like that! You may as well drop some enhancements to the player as he passes through levels/waves. Cheers!