I'm glad you enjoyed my game!
About the sound effects I must admit it was something that went over my head and when you guys mentioned it then I realized it was missing. As it's the first game I was doing all by myself I'm still getting the gist of priorities and now I see that while I was focusing too much on the level design some things have gotten left aside. But it's definitely something I'll prioritize on my next games.
About the music some of the previous apply here too and while I know some things about music theory in general I'm still not used to making video game music (like techniques or software). I wanted to make the music feel choppy like and 8bit or 16bit style but that time my knowledge just fell short.
I had some implicit goals and one of those were for the game to be completely textless, and didn't think at the time that I could do some graphical indications of the powerups usability, I just knew I didn't want to use text. What I did thou was locking the player in place until they figure out what the powerup could do, classic metroid style.
Thank you so much for playing and thank you for the feedback!