Neat work! I like the concept and the transition between segments/patterns is really cool!
Usually a shmup would take advantage of a smaller hitbox for the player, especially with such small projectile size, and making them pop would help quite a bit in the detail-heavy background. A bit of an I-frame would be really useful since the explosive projectiles are capable of swarming the player at some points (mainly the last level).
Great work overall!