Really polished a fun experience! I loved the different enemy types and their unique attacks, and the final boss was really good! I kept thinking maybe the boss is dead but then it kept going which was great! The upgrades are quite impactful and it's definitely satisfying to stack up on damage upgrades. I think my only nitpicks are that the boss difficulty was a bit weird. I'd say the hardest part of the boss was right at the beginning when you're surrounded by 3 different entities shooting at you, then after that it doesn't become much more difficult. Maybe it's just me? but maybe that stage could be brought on a bit later in the boss. I also think the 15 enemies could be more challenging. When they shoot the 2 enemy, it's very slow and feels a bit underwhelming. Maybe that enemy could also shoot (or if it already does maybe shoot frequently) or move a bit faster.
Otherwise, really great game and I love the UI elements and visual effects! Congrats!