Just like a work in any other medium, a game ends. Unlike other media, though, the ending of a game is seen as a reward—you don’t merely finish a game, you win it or beat it. For a long time, this simple concept of conclusion-as-reward has influenced the nature of game endings, and thus the nature of game narratives.
Cautionary tales, for instance, are very difficult to do in game format. Consider Hubert Selby’s novel Requiem For a Dream and its adaptation into film by Darren Aronofsky. The protagonists of the story in both formats are drug addicts, and the story is an unflinching view at the degradations they experience on their way to the bottom. It’s a powerful story in whichever medium you experience it in, but the realities of the subject matter demand a very particular sort of unhappy ending. If Selby had his characters abruptly quit cold turkey, for instance, it would be ludicrously out of character given their addictive behavior throughout the rest of the work.
But in a hypothetical Requiem game (bizarre as it may be to consider) that’s how it would have to end: at the very least, some sign of improvement in their conditions, some indication that things might get better for them, would have to take place. To be sure, there is a history of "unhappy" or "bad" endings in games, but they are almost invariably alternatives to the "real" ending. This is where nonlinear games come in.
For example, the time-travel themed game Chrono Trigger for SNES has upwards of 20 separate endings. The conventional finale upon winning the game in a straightforward manner is upbeat and resolves all loose ends in play, culminating in getting the romantic leads alone at last to enjoy the sights of a celebratory fair. Because this safe ending is in place, Chrono Trigger is free to explore other less savory possibilities: by savvy manipulation of the time travel system to win in unorthodox ways, players can see endings in which a corrupt dynasty gains control over the world, or where an untaken branch in prehistoric times leads to a bizarre evolutionary path, or even where the entire planet is destroyed by the game’s ultimate nemesis. Were any of these alternate scenarios included as the game’s sole ending, players would no doubt still be restlessly trying to discover the secret to the “true” path through the game, these many years later.
Fortunately, game designers are aware of this pitfall, and have come up with several ways to implement multiple endings so that both the requirement of a "reward" ending and the desire for a more challenging ending can be satisfied. These will be illustrated in a number of case studies, starting with: