One way to offer alternate endings is to present the player with clear-cut decisions throughout the course of the game, usually in the form of moral choices. It’s an old trick; as far back as 1987, Dragon Warrior presented the player with a menu upon meeting the evil Dragonlord. The player could either choose to fight the Dragonlord, which allowed him or her to complete the game by winning the battle; the alternative was to join the Dragonlord in world domination, which turned the screen red and ended the game instantly.
Disaster Report’s approach is essentially the same, though more complex. The player controls a reporter covering an artificial island city designed to alleviate overcrowding on the mainland. After an earthquake strikes, the player must find a way through the wreckage and off of the increasingly unstable island. Along the way, other survivors factor into the story, and the player must choose whether to side with this or that survivor, whether or not to leave the others behind to ensure his safety, and so forth. Though these decisions result in more interesting narrative branches than that presented in Dragon Warrior, they’re still made the same way: you simply choose an option from the menu, and then follow that path.
The advantage of this sort of divergence is that it’s easy to implement, for one. All a coder has to do is put vast chunks of the game behind basic if-then switches. For another, it’s easier on the player. If he or she doesn’t like the choices made in one run through, or if they result in a "bad" ending, all they have to do is pick something else next time.
The disadvantage is that, as an example of the narrative potential in gaming’s inherent interactivity, it’s fairly worthless. You can get as much from any in the endless series of Choose Your Own Adventure books, or from a few DVDs which allow "seamless branching" between two threads in a film. There’s also very little weight behind the decision the player makes. Many games allow progress to be saved at regular intervals, in order to prevent the frustration of having to start all the way at the beginning every time the player sees the Game Over screen. If a player keeps a saved game just before one of the crucial decision points, he or she can achieve an effect similar to holding one’s place in the aforementioned books, eliminating any sense of commitment to his or her choice. The lesser the investment in one particular choice, the lesser the impact of that choice’s logical conclusion within the game, which raises the question of why the developer allowed a choice in the first place.