FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
User Interface
The concept of a user interface should be familiar to you from computer software generally, but in a game the user interface has a more complex role. Most computer programs are tools of some kind: word-processing tools, web-browsing tools, painting tools, and so on. They are designed to be as efficient as possible and to present the user's work clearly. Games are different because the player's actions are not supposed to be as efficient as possible; they are obstructed by the challenges of the game. Most games also hide information from the player, revealing it only as the player advances. A game's user interface is supposed to entertain as well as to facilitate.
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The user interface mediates between the core mechanics of the game and the player (see Figure 2.1). It takes the challenges that are generated by the core mechanics (driving a racing car, for example) and turns them into graphics on the screen and sound from the speakers. It also turns the player's button presses and movements on the keyboard or controller into actions within the context of the game. If it does this smoothly and naturally, the player comes to associate the button press with the action. She no longer has to think, "I must press button A to apply the brakes." Instead she thinks, "Brakes!" and presses button A automatically. The user interface interprets the button press as the braking action and informs the core mechanics; the core mechanics determine the effect of the braking and send an instruction back to the user interface telling it to show the result. The user interface adjusts the animation to show the car slowing down and presents it to the player. All this happens in a fraction of a second.
Because the user interface lies between the player and the core mechanics, it is sometimes referred to as the presentation layer.
The user interface does more than display the outputs and receive the inputs. It also presents the story of the game, if there is any, and creates the sensory embodiment of the game world—all the images and sounds of the world and, if the game machine has a vibrating controller, the vibrations of the world, too. All the artwork and all the audio of the game are part of its user interface, its presentation layer. Two essential features of the user interface of a game are its camera model and its interaction model, as shown in Figure 2.2.
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GAMEPLAY
The user interface turns the player's inputs on the hardware into actions within the game world. The relationship between the player's inputs and the resulting actions is dictated by the game's interaction model. The model determines how the player projects her will, her choices, and her commands, into the game. In particular, it defines what she may and may not act upon at any given moment. Video games use a number of standard interaction models, including multipresence, avatar-based models, contestant models, and so on. In a multipresent model, for example, the player can act on different parts of the game world whenever she wants to, reaching "into" it from the "outside." In an avatar-based model, the player is represented by a character who already is inside the game world, and the player acts on the world through that character. Just as the visible parts of a game's user interface change during play, a game can have more than one interaction model depending on what is happening at the time. Chapter 8, "User Interfaces," discusses interaction models at greater length.
If a game includes a simulated physical space, or game world, then it almost certainly uses graphics to display that space to the player. The user interface must display the space from a particular angle or point of view. Designers usually imagine that a hypothetical camera is pointed at the virtual space, creating the image that the player sees. The system that controls the behavior of this imaginary camera is called the camera model. To define the camera model, think about how you want the player to view the game world and specify a system in your design documents that the programmers can implement.
Camera models come in two types, static and dynamic. Early arcade games, and many small games today, use a static camera model in which the camera always shows the virtual space from a fixed perspective. As gaming hardware has grown more powerful, however, game developers have begun to create dynamic camera models. In these models, the camera moves in response to player actions or events in the game world. Dynamic camera models require more effort to design and implement, but they make the player's experience livelier and more cinematic.
If a game doesn't have a virtual space (for example, if it's a business simulation that's mostly about money), the term camera model doesn't apply, and you have to explain the layout of your screen in your design documents in more detail.
The most commonly used camera models are first person and third person for presenting 3D game worlds and top-down, side-scrolling, and isometric for presenting 2D worlds. Chapter 4, "Game Worlds," discusses the question of game world dimensionality. Chapter 8 addresses the merits of the different camera models.
GAMES WITHOUT GRAPHICS____________________________
Many of the early computer games were text-based, designed to be played on a printing terminal attached to a mainframe computer. Text-only games still exist in the form of quizzes or trivia games, especially for small devices such as cell phones. Interactive fiction—text-only adventure games—has long since ceased to be a commercial genre, but it is still popular with a small group of hobbyists. Blind players can play text-only games using text-to-speech synthesizers. Also, a very small number of experimental audio-only games are intended for the blind.
