it definitely needs a tutorial. it took me a while to realize its main mechanics, like that the only way to die is the ring closing down on you, the limited ammo of the weapons, and that i had to shoot the smaller enemies to make the ring bigger.
eventually i reached the point where the ring just doesn't expand fast enough to let me reach the next boss item even if i shoot everything as soon as it spawns. i think you should relocate the boss item if the player hasn't picked it up after a certain amount of time
some weapons are definitely more infuriating than the others. the recoil of the revolver is insane and the flamethrower has extremely limited reach, making them inferior to most others. also, the shotgun is SO SLOW.
i actually enjoyed it a lot overall, i'm a fan of games like nuclear throne so some good ol' 2d shooter is always up my alley