FUNDAMENTALS OF GAME DESIGN, SECOND EDITION

The Structure of a Video Game

You now know how the core mechanics of a game work with the user interface to create gameplay for the player. A game seldom presents all its challenges at one time, however, nor does it permit the player to take all actions at all times. Instead, most video games present a subset of their complete gameplay, often with a partic­ular user interface to support it. Both the gameplay available and the user interface change from time to time as the player meets new challenges or views the game world from a different point of view. These changes sometimes occur in response to something the player has done, and at other times they occur automatically when the core mechanics have determined that they should. How and why the changes occur are determined by the game's structure. The structure is made up of gameplay modes, a vitally important concept in game design, and shell menus. This section explores gameplay modes and shell menus and discusses how they interact to form the structure.

Gameplay Modes

If a game is to be coherent, the challenges and actions available to the player at any given time should be conceptually related to one another. In hand-to-hand com­bat, for example, the player should be able to move around, wield his weapons, quaff a healing potion (though that may entail some risk), and perhaps run away or surrender. He should not be able to pull out a map or sit down to inventory his

assets, even if those are actions he may take at other times in the game. Likewise, a racecar driver should not be able to adjust the suspension of the car while driving it or drive the car while it's in the shop.

In short, unless a game is very simple, not all the challenges and actions that it offers make sense at all times. The player only experiences a subset of all the game - play, usually derived from the real-world activity (fighting, driving, constructing, and so on) that the game is simulating at that moment. The user interface, too, must be designed to facilitate whatever activity is taking place. The graphics dis­played for driving a racing car are necessarily different from those used for tuning it up in the shop. The camera and interaction models are different as well. When driving, the vehicle is the player's avatar on the racetrack, and the player usually sees the world from the cockpit; when tuning up the car, the player has omnipres­ent control over all of its parts, but the rest of the game world (the racetrack) is not accessible.

This combination of related items—available gameplay and supporting user interface at a given point in the game—collectively describe something called a gameplay mode. See Figure 2.3 for an illustration. In a given gameplay mode, the features of the game combine to give the player a certain experience that feels dif­ferent from other parts of the game; that is, other gameplay modes. Because the game offers only a subset of all its challenges and actions in a given gameplay mode, the player is focused on a limited number of goals.

The concept of the gameplay mode is central to the process of designing video games. Here is the formal definition:

GAMEPLAY MODE A gameplay mode consists of the particular subset of a game's total gameplay that is available at any one time in the game, plus the user interface that presents that subset of the gameplay to the player.

A game can be in only one gameplay mode at a time. When either the gameplay available to the player or the user interface (or both) changes significantly, the game has left one mode and entered another. A change to the user interface

qualifies as a change of mode because such changes redirect the player's focus of attention and cause him to start thinking about different challenges. Also, if the mapping between the controls on the input device and the actions in the game changes sharply, the player probably thinks of it as a new mode.

Many of the earliest arcade games have only one gameplay mode. In Asteroids, for example, you fly a spaceship around a field of asteroids, trying to avoid being hit by one and shooting at them to break them up and disintegrate them. The camera model and the interaction model never change, nor does the function of the con­trols. When you have destroyed an entire screenful of asteroids, you get a new screenful that moves somewhat faster, but that is all. From time to time an enemy spaceship appears and shoots at you, presenting new challenges (to avoid being shot and to shoot the enemy), but because nothing else changes, it isn't really a new gameplay mode. On the other hand, in Pac-Man you are chased by dangerous ghosts until you eat a large dot on the playfield. For a short period after that, the ghosts are vulnerable and they run away from you. Because this represents a signifi­cant change to the gameplay (and is a key part of the game's strategy), it can be considered a new gameplay mode even though the user interface does not change. As the designer, it's up to you to decide when the gameplay or the user interface has changed enough to be a new gameplay mode.

Figures 2.4 and 2.5 are screen shots from Empire: Total War illustrating two very different modes. Note that the on-screen indicators and menu items are entirely different in the two modes. The first, a turn-based campaign mode, shows an aerial perspective of a landscape. The player uses this mode for building cities, raising armies, and other strategic activities. The second, for fighting sea battles in real time, shows ship-to-ship combat. You cannot manage the entire empire from sea battle mode; you can only fight other ships such as the ones visible in the picture. The sea battle mode is essentially tactical.

Not all gameplay modes offer challenges that the player must meet immediately.

A strategy menu in a sports game is a gameplay mode because the player must choose the best strategy to help her win the game even though play is temporarily suspended while the player uses the menu. A character creation screen in a role­playing game or an inventory management screen in an adventure game both qualify as gameplay modes. A player's actions there influence the challenges she faces when she returns to regular play.