The main menu and fireworks effects were sick as hell! I also really liked the upgrade system. Initially, I thought the dash wasn’t working until I saw it as an upgrade option. It adds a nice sense of progression. The music was excellent, you did a great job with that as well.
As for the elephant in the room: I saw you mentioned the odd bullet direction was intentional. Take this with a grain of salt, but in my opinion, it didn’t quite work as a persistent gameplay mechanic. For it to work, I think there needs to be a clearer connection between your movement direction and where the bullets are going. I couldn’t get a solid grasp on the system at hand. Alternately, maybe there could be certain periods where the bullet direction becomes unstable.
Also, I saw in the description that you forgot to implement the theme, funny enough, I actually assumed the unstable bullet directions were your take on the theme! What did you originally have planned?
Good work overall, you clearly put a lot of effort into this!