Solid shooter! I like how the realistic boss sprites contrast with the simple background shapes. It gives off an indie internet game vibe that's perfect on itch.
I like the shooting mechanics, but I think the player isn't given enough room to dodge bullets. As someone else noted, it's basically impossible to complete the game without getting shot. I think if the bullet patterns had more space between bullets for the player to weave around them, it would feel more fair.
I'm not a fan of the moving colors on the terrain. I actually feel motion sick while moving through the level - probably because the colors move up and down.
Overall, solid entry!