Each world has several tracks, and you'll need to get as many stars as possible to unlock new worlds. Yes, you will be retrying many races to shoot for three stars, but this game is fun enough that it doesn't matter.
Though it might be hard to stop and look at the beautiful environments when you're trying to catch first place, it's impossible to miss some of the more scenic areas.
You can buy new hydro-jets, but they are not cheap. You can spend real money to get more in-game cash or do it the hard way -- by perfecting your racing skills through repetition.
