- prev and next buttons can hide when no more content. - improve help scene UI design to better support different resolutions. - fix end scene's bug of treating place holder as player's name when player directly hits enter button. - now even if player doesn't complete a stage, the score earned in this stage can also be added up to total score. - fix rank scene bug: need to click prev button to show result. - modify several properties to make them easier to distinguish and catch.