From the Super Mario Wiki
In this mission, Morton is hurling Cannonballs. Mario and co. can move left, center, and right, using the hammer to redirect the Cannonballs toward Morton. After a while, Morton will introduce Big Cannonballs, which can only be knocked back via Trio Hammer. Mario and co. also have five lives, and losing the last one results in a "Too Bad!" The mission is completed once the largest Cannonball is Trio Hammered back.
In the Hard Mode variant, Mario and co. only have three lives, and Morton throws Cannonballs at much faster intervals.
Hard Mode Objective
Names in other languages