As others have said, the style and presentation, you absolutely nailed it. It really doesn't take *any* time to be interested in the game instantly. The music also undermines that.
The gameplay, I have some issues with (and mind you, I love shmups and bullet hell games...^^). The dash mechanic is in my opinion really darn cool, but I feel like the entire design tells you not to use it? Going fast is pretty much counter productive because you cannot dodge the bullets properly then.
With a little more refined gameplay, this could easily be a good game.