Theory and Principles of Game Design

Principle : Make die rolls random, but outcomes statistical. While dice and other random number generators may appear to go against the notion that players should be in control of their fate, they are, in fact, a great way to mimic complex systems without having to simulate the myriad elements that make up the real thing. You don't make a game like Civilization by constructing accurate models of medieval weapons, or by modeling the human musculoskeletal system and pitting simulated humans against each other; what you do is come up with a statistical model for battles and incorporate that into your game's mechanics. Think of a roll of the dice as obtaining a single sample from a statistical model: The number that comes up is determined at random, but it's the state and rules of the game which determine what happens when that particular number comes up. Players win by making choices, manipulating the game state (or, sometimes, the rules) in such a way that random outcome...

Principle : Play without a purpose for new or better experiences. As you develop your game, engage in unstructured play to get a feel for the game's mechanics and the gameplay opportunities they offer. Approach it as a curious child would, by looking, observing, grabbing, manipulating, throwing, arranging, assembling, taking apart, and putting back together everything around you to develop an intuitive sense of how it all works. While playing, allow yourself to think of new mechanics or ways to improve the existing ones. Is there some mechanic that stands out as particularly fun or interesting? Could a seemingly unimportant mechanic be brought to the foreground? Is there something about the objects in the game that could make for a new and interesting mechanic? This is different from playtesting in that it's intuitive, unstructured, and completely informal. You're not looking for bugs, flaws or balance issues; You're just playing around while looking out for inter...

When the subject of free versus restricted saving comes up , people often end up conflating the issues of players being free to save their progress at any time and games requiring players to replay certain segments upon failure . The assumption is that the proper response to player failure is for the game to reload the latest save state, thus leading to a framing of the issue of loss of player progress in terms of free versus restricted saving. Unrestricted saving mechanisms are essential in modern games in that they allow players to quit the game at any time without losing progress. This does not, however, mean that loss of progress upon failure is an illegitimate mechanic. Countless commercially successful game designs that purposely incorporate just such a mechanic show quite clearly that loss of progress upon failure is a perfectly legitimate mechanic. Ultimately, the answer to the "free save" dilemma is not to design a game such that progress can never be lost, but to d...

F ailure by random numbers can occur whenever the random processes that determine failure aren't significantly influenced by the player's choices, giving players little or no meaningful control over the outcome of their actions. For the most part, games should be designed such that players may improve their chances of success according to the choices they make in the game, giving them meaningful control over their future.

Principle: Avoid responding to the player's actions with behavior that is contrary to reasonable player expectations, as it breaks the implied "contract" between the player and the game designer. Players cannot form a useful mental model of the game world when things happen unexpectedly or without an apparent cause. Players should be able to understand the laws at work in your game's environment, and to make appropriate deductions based on their understanding of those laws. If unexpected or incongruent behavior is desired, players should ultimately be able, by virtue of the game's design, to reconcile such behavior with their operative mental model of the game world -- which by its nature is allowed to change as the game progresses.

Principle: S ometimes a player's mistakes aren't really mistakes . If a player has no good reason to believe a particular action might lead to failure, then failure should not be blamed on the player. F ailure by surprise occurs when the player's actions do not appear as if they should lead to failure, because the relationship between action and outcome is either obscure or counterintuitive, or because the element that makes a particular action lead to failure is presented too late for the player to react to it. King's Quest and Dragon's Lair are known for this kind of failure mechanism, where the wrong move can easily result in unexpected death or failure 1 . A game should generally provide enough clues for players to anticipate danger, and should otherwise give players a fair chance to react to any surprises. Footnotes 1. See Ways to Die/Lose in King's Quest and Let's Fail Dragon's Lair v2.0 ( not safe for work ).

Principle : If a game requires a strategy guide or walkthrough to complete, it's broken. If the game may be completed without one but nevertheless provokes a not insignificant number of players to consult one, it's just as broken as before. Rationale: Completing a game should require no external clues. A player's failure to figure out a particular puzzle without outside help is actually the designer's failure to provide sufficient clues within the game. The game world is missing essential information; the game is broken. Exceptions: If a game mechanic explicitly involves the application of external information, this principle does not apply.

Some questions every game designer should ask during the game development process: Are the game's interfaces and user controls consistent throughout the game? If they're not, is there a good reason why they shouldn't be consistent? Do the inconsistencies make logical sense? Do the controls adhere to known conventions for the game's genre? If not, in what ways is the game's control scheme superior to that of its predecessors? Are there objects in the game that behave contrary to reasonable player expectations? Are there objects that look like they should do something they don't do? Are there objects that do things that are not suggested by their form? Does the player feel lost ("where am I" / "what am I supposed to do next") when I don't intend him to feel that way? If I do intend it, do I have a very good reason for it? Does my approach convey the desired emotions, or is it merely frustrating? Does the game provide sufficient cues for t...

The issue : Certain kinds of games require that players keep one or more specific goals in mind as they play. Players who return to a game after a long absence may find it difficult to remember what they're supposed to do next, which may impede their progress. Resolution: Provide some sort of reminder of the player's unfinished tasks. This may assume such different forms as a list of pending and completed goals (Psychonauts), an in-character reminder of pending goals (Dragon Quest VIII), or a video log of significant cutscenes (Ratchet and Clank: Going Commando). If any of the tasks require knowledge of specific details previously revealed in play, the player should likewise be reminded of those details.

Defeating an enemy; overcoming an obstacle; surviving in the face of adversity: success and failure are at the very core of the game-player's experience. Games offer players a number of choices, some of which lead to success and some of which lead to failure or non-success. Together with the challenges presented to the player, the fact that the player might fail lends significance to the player's choices and actions. Although failure can be a negative experience, it is also the very thing that makes success meaningful . There are two kinds of failure in games. One kind of failure concerns the player's inability to satisfy a particular success condition that nevertheless remains satisfiable, and another kind of failure takes place whenever the player encounters a particular failure condition . While the first kind of failure is simply a failure to succeed, the latter kind calls for a particular response to the player's actions. The manner in which a game responds to pl...