"Fortunately, I eventually found where all the actual puzzles were hiding; they're in the co-op campaign which I played through with one of my fat friends. With the addition of two extra portals to play around with, the puzzles are bigger and better and satisfying to solve through teamwork. If you need to swiftly make friends with someone, like a future father-in law or armed burglar, then you couldn't find a better ice breaker. I just don't think it has any replay value whatsoever. If you played it again with another fat friend, you'd just get sick of lugging the ball and chain around and they'd resent you for not letting them figure shit out on their own. So, make doubly sure that your armed burglar isn't an avid PC gamer."