Cool result for seven days, on a genre i enjoy to play ^^
I like the overall setting of the game. One thing i had to mention. For me it seemed to be a bullet hell, not bullet heaven like u wrote, cause the enemies seemed the only one to have the bullets on their side. (But please correct me there, if i was just to bad to get to the point where the bullet escalation comes from me^^)
The mechanic for the ultimate was very cool to me. There u feel really powerfull and it was satisfying to slice through the masses :D
My points for improvement.
Let the player strike in the direction he is looking. Don't know if it was a design decision, but now it didn't felt so intuitive to me.
The hit feeling was okay but i think with some more polishing and juice u can get a bit more out of it. Also it felt like the enemies immediatley make damage on me, when they arrive in range. So go for an attack always was pretty risky cause u very often also get hit, that doesn't feel so satisfying atm for me.
But overall a pretty cool game that has potential for some nice improvement :)
Good work!