I wouldnt call secret rings a "must buy" but it's definately awesome. What I really like is how it has you going back and forth between worlds, beating levels. And you'll want to play the same levels over and over again to get bronze, silver, or gold medals to unlock more stuff. Come to think of it, the more I talk about this the more it sounds like a racing game. It's definately racing-game-esque. Whatever. It's a frickin tight game and you MUST rent it at least. I'd say if you can find it for $40 or under, then it's a must buy.