Nice little game. If your inspiration is Japanese '80s arcade shooters, it's worth taking a close look at them (and their 90s and 2000s sequels) to understood how they held the player's attention. A mistake I see in this game and many other Western shmups is giving the enemies too much health. Slowly chipping away at bad guys gets boring, usually the rule in these games is that small enemies die in 1-2 hits and larger enemies live just long enough to test whether you can evade their pattern of fire. The challenge comes more from weathering swarms of enemies than from any individual foe. Displaying lifebars above non-boss enemies is a sign it takes too long to destroy them. The pacing of arcade games is also instructive; levels usually last just a couple minutes and the enemy patterns are constantly varying.

Other than that the music and aesthetics are great, though there is some funny aliasing of sprites and JPEG artifacts in the backgrounds. The key to this kind of aesthetic is a crisp look.