Got to wave 6. Flying controls are a bit janky but it was fun to figure them out. My first instinct was to look for an "invert y"option, but in the end I got used to it anyway. Going straight up gets pretty weird, might be related to euler angles instead of quaternions or something (I had this stuff figured out for my filesize jam game but now I forgot).
I know that the endless waves are temporary, but in my opinion even just for a demo you should make so it's not so open ended. You could just set a target number of waves, and when the player gets there show the vampire girl and print "thanks for playing". You can even give an option to continue anyway after that, it's just a way to give an objective and to make the player feel he got something out of his time.
I thought the orbs worked well enough for ui, no complaints there.
I think mipmaps on textures and/or antialiasing would make it look better, but I don't actually know anything about 3D.