Great game! I always liked Nyan Cat! :-) Only few things:
1. Sometimes I am not sure what exactly I did to unlock some of the medals;
2. I would definitely recommend changing the behaviour of the game after dying, because if you die on a very advanced level, the still moving background makes 2 things complicated:
a) it makes difficult to change the body/head, because it is simply covering the buttons;
b) after you restart you can lose a life or even 2, because before the previous background disappears, you are sometimes not sure where exactly you are and which obstacles are the current ones.