Once I reach the bottom of the page I can keep rotating of course and the page doesn't scroll further than the bottom. But if I rotate say 100px past the bottom

Once I reach the bottom of the page I can keep rotating of course and the page doesn't scroll further than the bottom. But if I rotate say 100px past the bottom of the screen I need to rotate backwards 100px before the screen moves up again. Basically there's a counter somewhere that needs to freeze once I hit the bottom of the page. Mobile Firefox