Based on the overall progress bar, I would assume there is a third boss, but my skill doesn't let me go through the second one.
Another thing I appreciate after replaying it 4 times is that the game progresses in an interesting way with my skill, allowing me to discover new moves (e.g. collecting a lot of bullets in one place and then manipulating the boss to be there). That doesn't help me with the lightning though :<
Please consider adding WASD controls!