Great game, but unfortunately it's got bugs. In terms of the 'hover feather' not registering and making Alto hover. Just turns him blue, but he doesn't hover over rocks. Similarly, not registered in clearing challenges. One of these is 'collect both the hover feather and coin magnet in one run' - impossible to do though as the game is not recognising when you pick up both of these perks, essentially meaning you're stuck on that level. Suspect the devs have stopped bothering fixing issues.