FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
The Nature of Time
In a single-player computer game, you maintain a great deal of control over the relationship between game time and real time. Most games run at many times the speed of real time, and a player often experiences a simulated day in a game world in an hour or less of real time. You can also hand over control of the speed of time to the player when you want to; it's not uncommon for players in combat flight simulators to speed up time when flying to and from the combat zones and then slow down to real time again when they get there. Finally, you can skip time entirely—useful during periods when the player's avatar sleeps. You can blank the screen for a moment and then put up a text message that says, "8 hours later... ," and continue with the game.
But you can't use any of these options in multiplayer games. You obviously can't allow some players to move through time at different speeds than others, and you can't skip time unless you force all players to skip that time together. Although
game time might be faster than real time, game time must proceed at the same fixed pace for everyone.
As a result, you must be careful about designing time-consuming activities. EverQuest, for example, employs a mechanism called meditation, in which players simply have to wait around for a while to restore their magic powers. There's no way to speed up this process—it literally does involve waiting. Nor can they log out of the game while meditating and log back in again later when the meditation process finishes. Players can't even switch to a different process on their computers. Verant, the developers of EverQuest, eventually built in a mini-game for players to play while waiting—a patch but not a real solution. If your game contains features so boring that you have to distract the players, you need to rethink the features.
Single-player games can be stopped and restarted at the player's discretion—a key consideration for designers of such games. If the player can save the game, he can essentially reverse time by going back to a previous point in the game and replaying the game from that point. This robs single-player games of the emotional impact of events because anything that happens, good or bad, can be reversed by reloading a saved version of the game. You can design the game to include some inevitable events, but of course, the more of these you include, the less interactive the game is.
In an online game, time is irreversible. Even if you had a convenient way to reverse time, you can't reasonably ask all your players to agree to reverse time to an earlier point (although the managers of some persistent worlds have had to roll back to a saved state when the game got into problems). In the ordinary course of events, when an event occurs in an online game, it's done and can't be undone.
