What makes a computer game replayable? And why are some replayable and some not?

In principle, any game should be replayable. If you went down to the toy store, bought a board game in a box for twenty or thirty dollars, and then came home to discover that you could only play it once, you would be rightfully wrathful. Yet, this happens fairly frequently with computer games, and our customers are more or less resigned to it. Replayability, however, is no accident: it's something we as designers can build in on purpose…if we want to.

Let's start with the question of whether we want to. From a purely mercenary standpoint, replayability isn't always a good thing. If a game is endlessly replayable, our customers have no reason to go buy another game. We need them to buy new games to keep ourselves employed, so we have a financial motive to build a certain lifespan into our games. However, I don't know of any developer who actually feels this way. For one thing, most games already have a certain lifespan because of galloping technology; there's no need to build one in artificially when Intel and AMD are doing their best to make sure our games are obsolete in a couple of years no matter what we do. But more importantly, most of us have some creative pride. We want people to go on playing our games for a long time. We respect games, like Civilization and Myst, which people continue to play for years, and we respect their designers for having achieved such a thing.

	We respect games, like Civilization and Myst, which people continue to play for years, and we respect their designers for having achieved such a thing.

So assuming that we do want to make a game replayable, what issues influence replayability? Leaving aside technology, which we can't control, how do we design a replayable game? In the first part of this article, I'll address the effect of narrative on games, and in the second part, I'll look at game mechanics.

Narrative in games - that is, the storyline, when there is one - tends to be fairly fixed and fairly linear. Despite 25-odd years of more or less haphazard research, no one has devised a really satisfactory "branching storyline." When people replay the game to see branches that they missed the first time, they tend to hurry through those parts that they've already seen, paying little attention. And if the narrative is linear, as in Starcraft or Diablo, once you know the story, it doesn't provide much motivation to play the game again. Fortunately, those games offer sufficiently interesting gameplay that they're worth playing again even if you already know the story. But for adventure games, the story is most of the reason for playing them. Once you've solved all the puzzles and you know the whole story, there's little reason to do it again. The more important narrative is to a game, the more of a disincentive it is to play it again.

But I don't think it has to be that way.

If you drive to the far northern tip of Scotland, where puffins nest among the sea-cliffs and the mist swirls over the grass even in high summer, you can stand and look north across the treacherous waters of the Pentland Firth to a low, treeless archipelago: the Orkney Islands.
And if you take the ferry over to the Orkneys, you can visit dozens of ancient stone monuments left by people hardier than we: Neolithic farmers, Picts, Vikings. Among them is a beautifully preserved little village, Skara Brae, where all the walls, floors, and even furniture are made of flagstones. Nowadays you can stand on the wall-tops, look down into the roofless rooms with their beds and shelves and cupboards all of stone, and try to imagine what it must have been like during the icy howling darkness of a North Sea winter's night, five thousand years ago. People dressed in skins, huddling around the hearth in the reeking gloom, burning such driftwood as they could find, the only light coming from the fire.

How did they pass those endless winters? Working, certainly: cooking, sewing, tending babies and mending tools. Playing, certainly: singing, talking, telling jokes and laughing. Doing what humans do: eating and sleeping, making love and giving birth, falling ill and dying. And throughout it all, the thread that spans the generations: telling tales and listening to them told.

Nowadays we have so many stories to choose from that a man could spend his entire life reading, watching television, going to the movies all day, every day, and never once hear the same story again if he did not want to. But in ancient times, the tales were fewer, and memorized, not written down. Perhaps their telling was the province of a privileged group, or even a single person: the bard, the singer. And so by the time she had reached old age - that is to say, her fifties, if she survived childbirth - a woman must have heard the same tale many a hundred times.

Why did they bother? Why did they care? Was it because any story, no matter how many times heard, was better than silence? I doubt it. In silence inheres the potential for all stories, good and bad; in speech, the potential becomes the real. It is better to hear only silence than to hear a bad story told again. I believe the reason our ancestors listened to the same stories again and again was that they were good stories.

With so many tales to choose from, we now assume that once we know the plot there's no longer any point in hearing the story again. This is true for most of our stories: is any given episode of Kojak or 21 Jump Street that worth seeing a second time? Probably not. But there are a few tales that we do see, or hear, or read over and over. We drag out A Christmas Carol year after year, and even if Tiny Tim is too saccharine for modern tastes, the story of a bitter old man's redemption is not.

I usually re-read The Lord of the Rings, or parts of it, about every 18 months. I know it backwards and forwards. I know I'm not going to learn anything new about the plot. What brings me back, what keeps my attention, is not the tale but the telling.

Consider the following sentence from near the end of the book. It occurs at the penultimate moment, when Frodo is standing at the Cracks of Doom with the Ring in his hand. The Dark Lord has suddenly become aware of him, and knows that his very existence hangs by a thread.

From all his policies and webs of fear and treachery, from all his stratagems and wars his mind shook free; and throughout his realm a tremor ran, his slaves quailed, and his armies halted, and his captains suddenly steerless, bereft of will, wavered and despaired.

Read aloud, this sentence rings with the rhythms of poetry. The first two phrases have a parallel construction, and in fact, they are perfect iambic heptameter and hexameter respectively:

From all / his pol- / i-cies / and webs / of fear / and trea- / cher-y
From all / his stra- / ta-gems / and wars / his mind / shook free

They even rhyme. The next phrase sounds like Anglo-Saxon alliterative verse, with its repeating initial consonants:

and Throughout his Realm / a Tremor Ran

and with the exception of the word "and," it too is composed of iambs:

through-out / his realm / a tre- / mor ran

Then we return to parallel construction with "his slaves quailed, and his armies halted." After that the rhythm begins to break up, just as the Dark Lord's regimented, mechanized world began to break up. Did Tolkien do this deliberately? There's no way to tell, but he was a poet who knew everything there was to know about the English language, and consciously or unconsciously, his mind used that knowledge to work his material. At a moment in the story when only poetry could do justice to his vision, he employed its methods to great effect. This is one of the most powerful sentences in the book, but it's the kind of thing you only notice on a second, or third, or twelfth reading.