I liked the choice of music and the art was decently cohesive and nice. It took me until 900 points to ever see a shield drop, and by then the game had gotten a bit stale. I also found I kept losing the ability to move when up against the left side of the screen, which was annoying. I didn't really get the presence of the enhance theme at all, but I do think this was overall pretty decent.
Brainshaker mode is just whether or not you want screenshake on? Might be better to refer to it by what it's commonly known as, though forgive me if it's just a translation thing. I know some people can really be put off by screenshake and as someone who recently failed to give that option herself, I'm glad to see you include it :)