I don't know if it's intentional but I absolutely love that there can only be one bullet! It forces you to be aggressive in a game where the normal thing would be to hug a wall and stay as far away from the boss as possible.
It's unfortunate, but it seems to happen only on the first run of the game and performance improves on subsequent runs. Sadly the first impression is the most important.
Siendo honestos, tengo un sesgo muy fuerte en favor de juegos difíciles xD. Mirando en perspectiva, implementar un "modo práctica" sería una buena solución.