really awesome, i like it. i am working also on a box2d + libgdx game (something like climb hill)
i can see how many "little details" you put in your game. graphics are also great.
what i would suggest you is to remove some animations from your menu.
i think you put to much animatios (button scroll, down, up,..) maybe animate all control together (fade or scroll) instead of each control by it self.
but beside that it is GREAT! Thumbs Up! wish your lot of luck with your new game