I hope this game one day outgrows the simple wave based arcade formula. I think this could do well as a 'Simulator' like this : Pigeon Simulator on Steam .
There seems to be a stealth mechanic? I might be imagining it but I felt like when I flapped my wings close by enemies would become alert. If that's the case I like that a lot, it should be more clear, I shouldn't be wondering if that's actually a mechanic or just in my imagination.
I would like to feel more agile / in control of Batty, I believe some kind of lock-on system would be cool. Of course I think you should be careful about adding in too many new mechanics willy nilly.
The music does not quite fit, would like something a bit more gothic. Voices are great.