Sid Meier's Alpha Centauriii. Alpha Centauri makes excellent use of an interface design principle -- that of unity of design. All actions in Alpha Centauri are done from a single screen. The center of the screen is a worldview of whatever part of the map of "Planet" (the fictional planet upon which the game takes place) is being examined. Unlike many other games, the action never leaves this screen. (Figure 1)
Not only does the pop-up screen effect look aesthetically pleasing, it also means that actions taken with the interface map neatly to the user's experience. When a button for a more detailed screen is pushed, the detailed info smoothly glides into place as if it were a real screen. This also provides what psychologist Donald A. Norman calls "knowledge in the world"iii. In other words, the user does not have to memorize a series of steps and actions, instead -- they are presented immediately on-screen in such a way that the user can examine the possible options, choose one, and even learn more about it by right-clicking before committing to the action. Since the game is not under time-pressure, this means that inexperienced users can browse all possible actions carefully, while over time, as knowledge becomes "in the head" (Norman, Design of Everyday Things) actions become speedier and more efficient.
Alpha Centauri is very good at putting "knowledge in the world." At any time, when a unit is selected on the main screen, it can be given commands by right-clicking it. Right-clicking causes a menu to pop-up much like a file in Windows98. This maps to a well-known convention; right-clicking things causes a sub-menu to pop up. It also means that keyboard shortcut keys do not need to be memorized, instead, the command can be chosen from a list that exists whenever it is needed, in precisely the place that it is needed. While this is convenient, it does violate some of the aesthetic appeal of Alpha Centauri; in many places the interface is made to resemble real-world objects, but, while in the real-world, we can not right-click on subordinates and be presented with a menu of possible options.
The user in Alpha Centauri is given excellent feedback; when a command is issued that is impossible, a pop-window appears explaining exactly why it is not possible. There is also an audible cue to indicate that the command failed, and the user can't move on until the dialog box is dismissed by clicking on "ok." The feedback is detailed, immediate, and always includes a picture that ties it in to the originating error. This is an almost textbook perfect example of how feedback should be provided.
The interface in Alpha Centauri is visually very balanced. Important screens and warnings always appear front and center -- while subsidiary data, reports, and information appear off to the side. The effect is such that the eye can easily scan for the information needed, and tracks the results of actions easily.
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