The visual of black hole is awesome.
Though the control is not intuitive for me at first, I think the idea the ship is accelerated by the black hole is cool.
The UI of menu is nice, but there is one thing I have to mention.
The setting is disabled and the text is gray, while in the mode choosing part, the one you choose would also be gray.
It's a bit confusing that whether the gray one is selected or not.
The game mechanic is interesting, especially the bullet would be influenced by the black hole.
Yet, I would consider cutting down the number of total holes and add some other stuff, so that players won't be doing the same thing for a little bit too long.
Anyway, you had done some great work!