I want to start by saying that the name of the game is just delightfully well thought!
And the fake box art for it is just an amazing addition to the whole package, so kudos for that as well!
The fact that it is a rhythm game already wins a bunch of points in my book and it's a really nice one as well! The game is simple and direct, just approach the enemies and press the buttons in the correct tempo. Couldn't have clearer than that!
Like mentioned by someone else, the game lacks a bit of audio, although the battle theme compensates for bringing the GB feel to it, plus, I really really enjoyed to hear it! Although, the game becomes a bit repetitive at times, having always the same music to accompany you as you play throughout the rhythmic battle. Even though I think the button patterns were always different in each battle? If so, that helps a bit with the whole repetitiveness issue. Maybe have 1 or 2 more musics in the mixture so it doesn't get so dull over time!
All in all, it's a really nice game and the work put on it shows! Congratulations!