On the subject of getting better at coming up with gameplay, I would recommend considering, once you know who and what the player is going to be playing as, trying to consider how that person or thing would view its own movement. Just given how they move, I don't think actual flies feel the physics of their own bodies much. As such, I would've recommended much higher acceleration with a straight cap on movement speed, so that the feeling of inertia is nearly non-existent.