Instructions
Clear all eight worlds in the game, beating the bosses in each world. Beating Bowser at the end of the game will unlock the ninth world.
Collect all of the star coins in each world; there are three star coins, some in hidden locations, in each level. For every world you collect all the star coins in, a new level will be opened in World 9. For example, collecting all the star coins in World 1 will open Level 9-1.
Play through all eight levels in World 9 to defeat the game's "Challenge Mode."