Last month I looked at the way narrative affects game replayability. This time I'll be looking at how replayability is affected by the game mechanics themselves.

Obviously, the single most important contributor to a game's replayability is its playability in the first place. If a game is badly balanced, if it has a poor user interface, if it seems to be lacking essential features, then it's not going to be much fun to play, much less to play again. But there are specific design considerations that influence a game's re-playability, and those are the ones I'll be talking about here.

Let's start with your basic single-player computer game. Whether a player perceives such a game as replayable depends to some extent on what kind of a player he or she is. Consider our two old friends, the core gamer and the casual gamer. (See my earlier column, "Casual versus Core" for a discussion of these folks.) Since a core gamer's primary motivation is beating the game, as long as the gameplay is interesting and above all challenging, he will continue to play that game repeatedly until he has beaten it, even if the gameplay is very similar every time. The core gamer has no problem with a game like Pac-Man, because even though Pac-Man is a deterministic game that behaves exactly the same way every time you play it, it offers a huge amount of gameplay. Pac-Man contains 256 levels, and very, very few people have ever played them all. The core gamer doesn't mind a game that plays the same way every time, as long as he's got an entertaining challenge to overcome.

	Pac-Man contains 256 levels, and very, very few people have ever played them all.

This is why arcade games are designed for core gamers, and why they make so much money. Most arcade games provide large numbers of levels and progressively increasing difficulty, and many have deterministic gameplay. The deterministic gameplay allows the core gamer to move swiftly through the early, easy levels, and get up to the harder ones where the real challenge is. Most arcade games are also ultimately unbeatable; they simply get faster and faster until no human being could possibly keep up with them. This means that the object is not actually to beat the game, but to beat your own personal best score, and that's something you can always try for no matter how many times you have played the game. Core gamers give up on arcade games once they become tired of the gameplay or they reach a point beyond which they simply cannot improve, and once a core gamer does beat a game once and for all, he's seldom interested in playing it any more. The pleasure comes from winning, and since he now knows how to beat it, the challenge is gone.

The casual gamer, on the other hand, plays not for the exhilaration of victory, but for the joy of playing the game. It's not enough to simply supply the casual gamer with a tough challenge and let her go at it; she has to be having a good time, and to lure her back again, one thing the casual gamer needs is variety. The game has to be different the next time she plays it.