Once I got the hang of flying its pretty fun but I feel like it's missing something to spice things up after awhile. I played a bit of endless mode and by wave 6 it didn't feel like much has changed between waves to get a sense of progression. Perhaps you need more enemy types? I know batty targets only people but maybe if there was stuff in the air to target as well gameplay could feel more varied.
The help menu extended off the window in fullscreen for me so some of the information was obscured. You should probably be able to scroll with it if it's going to be that long.
The hitbox / hurtbox feels a little wonky? Sometimes I would fly over the heads of enemies when I feel like I should've hit them. Almost as if batty's hitbox extends only above her model's body and not below it at all. Also it's really hard to dodge the enemy that shoots orange balls at you.
There should probably be some sort of invisible wall at the bounds of the level. For fun I tried seeing how batty far can fly away from it but since the render distance is really small the level disappears from view pretty quickly and it becomes really hard to orient myself without any reference to try and get back.
Voice acting is pretty funny. I enjoyed the overall lightheartedness of the game. Music is comfy.