I like the graphics a lot! Really cute art style, I love how detailed the boss was (even if it did just glide around, haha). The audio was a bit too quiet though.
I think the only problem is that it's too simple at the moment. All the enemies just shoot towards the player, the only difference is how the enemy moves. I think the game could benefit a lot more from different bullet patterns, like rings, or shotgun bursts. I think a minimap could benefit the game a lot, too.
Still a pretty fun game overall! Definitely could go pretty far with some polish.