Well this seems like a very polished and well-done game, I love it! 5/5.
I'm also a sucker for the art of the girl, for whatever reason. I love that sort of depressed look you've given her.
How is an 'under rating threshold' comment in the BEST COMMENTS?!?!
On the game: Easy, but fun for a short time. I recommend a level editor, multiple cannon-ball types and more levels with multiple cannons added.
Mega boring once emporer is defeated. Should be able to repeat bosses too... (Just for the sake of repeating, not getting more gear - or maybe if you sold that gear, you get it back, but can only have 1 at a time)
Hiding her eyes was key, it masks her emotions. I used the same trick when conceiving of the young lad in the original.