Plays like a level builder where you have to get the difficulty just right, neat idea! I think the variety of attacks is just right, there's enough variety without being too confusing or overwhelming. I did encounter an issue where the player spawned in the upper left corner during my boss phase, I had to shoot a bullet in the corner for the player to return to the game area. Other than that, the game runs well and I don't have any other issues in terms of gameplay. Great take on the theme, nice work!