While I think it'd be cool to be a ninja, this game actually makes me reconsider! It's not much of an action game as it is more "sports" oriented. You either deflect objects thrown at you (requiring VERY good timing) or busting up stuff. The latter requires the proverbial, frenetic back-and-forth joystick movement to gain enough power -- and within a time limit, to boot -- to break said objects.
The one frustrating thing about the game is that there is no margin for error. So most of the time you find yourself with low scores and not qualifying to get to the next round. At least you don't get those problems playing under an emulator. :)