not bad, though there is a lot of room for improvement
-ship is sluggish, the speed powerup actually got the ship to what i feel standard speed should be. it even feels to slow with the engines upgraded to max
-ship is too tanky/enemy shots are too weak, i didn't need to dodge a single shot as when i had the regen powerup, the regen was faster than the enemy ships' damage
-hitbox is too large- if you do make the enemy shots more powerful and make the ship faster, shrink the hitbox, the massive hitbox made tanking the only viable option- and as i said, tanking was super easy
-powerups too overpowered. invulnerability was actually less useful than regeneration- enemies did less damage than the regeneration gave, and there appeared to be no cap on HP. i invariably finished levels with more health than i started with
-very little risk vs. reward. bullet hell is all about risk vs. reward, there was no reason to go for close dodges (well there was no reason to dodge at all but i digress).
basically, it wasn't bullet hell, if you want something to aspire to, have a look at touhou project, you don't need to follow that template exactly, but it's a very good idea to look at it, as it is the quintessential bullet hell, use it for inspiration.