Good, but couldn't make itself stand out
It started off okay with the nice upgrade screen and easy levels, but the whole game felt like the same level. It never got hard, the bosses didn't really do anything special or challenging and the only enemies that ever were hard are the ones that fire in 8 directions rapidly while flying past you.
My advice: play some more arcade shooters like Deathsmiles and Touhou. Then you'll know what a real shooter feels like. Or add difficulty levels, because this game is way too easy for anyone who's played shmups before.