Extra levels:
Beat all 10 levels in World 1 without using any continues on Beginner difficulty to unlock 10 more Beginner levels. Beat all 30 levels in Worlds 2 through 4 without using any continues on Advanced difficulty to unlock 10 more Advanced levels. Beat all 50 levels in Worlds 5 through 10 without using any continues on Expert difficulty to unlock 10 more Expert levels.

Master difficulty setting:
Beat the 10 extra Expert levels without using any continues to unlock Master difficulty.

Thanks to Revolution reader Mark Madd!