In all the talk of graphical downgrades no one seems much preoccupied with 'why?'. Why build something and then proceed to tear it down, piece by piece, in the hope that ever more diminished expectations about the final product won't be severe enough to...
Use your double jump to adjust your trajectory during a jump.
Explore alternative routes to bag all of the coins and track down that elusive star.
Checkpoints will allow you to restart midway through the level, so be sure to seek them out.