It's an entertaining game, and a good use of the theme. However, I have a few suggestions. Instead of increasing the spawn rate of the projectiles to increase difficulty, I would increase the speed of the level (missiles, energy wall) to make it feel more frantic and skillful. I would also add a stamina bar to the player's flight, since it seems the optimal strategy is to camp at the top. Other than that, great use of the theme in gameplay and a lot of fun!!!