When Interfaces Break Down
An interface is a medium that provides a person with access to the literal and virtual parts of a machine, that allow him to control the mechanism. ...look at the automobile. ...the interface is deceptively simple - a wheel, a few levers and switches, a couple of pedals - but it gives us control of a very complex machine. It isn't necessary or practical for the driver to understand exactly what transpires in the bowels of a car when the shifter is moved from forward to reverse - in fact, the task of navigating a car through busy streets would be impossible if the driver were also responsible for synchronizing the flywheels within the gearbox to mesh with the transmission. A shift lever with a few letters stamped on it is a perfect interface: it gives only the essential information, and allows only the pertinent actions required to shift into one of 6 gears. If automobile interface were prone to breakdowns, (as Web interfaces often are) - if R sometimes meant 2nd gear, and shifting into neutral just played a message about the benefits of Neutral - most users would abandon driving in a hurry.

Figure 2.1 Interfaces link people with the complex workings of machines. Simple interfaces that give users control of one thing, such as the gear shift in a car, are relatively easy to grasp. Be aware, however, that the simpler the interface, the more noticeable its failure to live up to the user's expectations will be.

Fig 3-6
The size and shape of real world control points ≠ buttons, switches even archaic dial holes ≠ are based on the size of a finger tip. This may explain why virtual buttons tend to convey usability best when they adhere to a narrow range of shapes and sizes. Note that fingers have an avatar in the computer: the cursor, which determines the minimum sizes for links and buttons. Fig 3-6b This grid shows the relative range of shapes that feel best as buttons without the aid of common affordances like beveled edges. The more static obtuse shapes seem to work better than say, a triangle. A hexagon, for instance, relates better to round, real-world buttons such as elevator buttons, whereas triangles have a stronger association with alert symbols and signs.

Phases of Visual Cognition
When designing icons, be mindful of the phases of visual cognition. People first recognize an object's basic geometry. Then they take in its subtler shapes, shadows and details. Finally, they recognize its unique and defining characteristics. Facial characteristics, for example, are registered most quickly when they are more geometric. People notice eyes quickly because they are round, whereas the more complex mouth shape is recognized later. (See Figure 5.18) An icon's essential characteristics should be rendered as simply and geometrically as possible to help the user quickly recognize it.

Figure 4.15 Part of Dwight Eisenhower's appeal to the electorate of the 50's was his resemblance to Everyman. If I was confronted in a dark alley by the ghost of Dwight Eisenhower, I would turn and run after maybe 3 seconds - the amount of time it would take me to recognize him. But I'd turn and run in a nanosecond of seeing the Minotaur, whom I would never mistake for Dwight Everyman.

The rounded corner keyline border in the Macintosh style conveys usability abstractly by referencing a user's tactile sense (consider the cursor a virtual finger). The curved handle of the tool on the left looks more user-friendly than its hard-edged counterpart on the right.

Figure 4.17 Affordances that are native to the computer still draw upon real world experience, but more abstractly than 3-D modeling does. The original Macintosh interface relied on abstract systems of affordances that required an initial learning curve, but were essentially grounded in common sense.

Antialiasing and Readability
c. A letter can't be moved less than the width of one pixel. Anti-aliasing implies a fraction of a pixel by using a combination of shaded pixels.


Faithfully approximating a typeface's subtleties is less important than the clear crisp use of vertical symmetry and white space in and around each letter. Return to aliased type, at least as a starting point. Use rectilinear letterforms that take advantage of the computer screen's square and sharp pixel edges to make a simple, clear-looking button label. e. If the letters are too jagged or flat, softening curves and slanted edge with transitional-colored pixels achieves the same end as anti-aliasing. But by working selectively, a designer can choose only the most important pixels to soften, maintaining a hard baseline and letter spacing. f. The pixels indicated in red above show an even distribution of white space - critically important for comfortable reading.

Form Elements
Figure 5.1
Form elements are essentially lists of options. When the user selects an option and clicks the submit button, the information is sent to a script, which often resides on a server but can also reside on the client side. 2. The script then translates the information into a useful format, 3. and often delivers it back to the user.

Figure 5.21 When a user selects an option, the row is highlighted. The color of the highlight can be customized by the user in both the Windows and Mac operating systems .

This menu has a background applied to it with CSS which is similar to the highlight color. It appears as if every option in the list is selected, when in fact, none are.

Metaphor & Iconography
Figure 10-3 The operating system would still function if other, equally-familiar metaphors were introduced, but the system would cease to be elegant. Documents can be placed on a bulletin board, for instance, and deleted by fire, but mixing concepts makes the relationship between elements more complex, and degrades the desktop concept. End sidebar 10-3 While illustrating a metaphor through interface elements helps support the user's mental model, over-illustration can be distracting. Strict illustration can make the user too conscious of the metaphor. (See Figure 10-4) Fig. 10-4 Element design should support the metaphorical system without interfering with the task at hand. Overly-illustrative icons draw too much attention to themselves, making it harder for the user to forgive an interface's inability to duplicate reality.

Physical Space vs. Virtual Space

Figure 7.6
This airport directional sign is literally accurate, as the arrow points to the destination, but it is incorrect in mapping movement in real space. People seem to naturally interpret the sign as if it were lying on the floor.

Figure 7.10: Tabs as Content Filters While none of these four tabs are strictly related to each other, three of the tabs - Books, Music, Electronics čare purchase categories. Even at a glance, "Preferences≤ does not belong in a group with Books, Music, and Electronics. Preferences affect all purchases, and thus arch over every category, so they should be represented in another way. Separate the tasks of defining preferences and profiles (which will affect every purchase) from the actual item categories. Fig. 10-15b This logical model shows Books, Music, and Electronics (things to purchase) as parallel planes, and Preferences, which affects every purchase as a plane that touches the others.

Holding a set of magic content lenses up to the page helps illustrate what parts of the interface should be placed behind tabs, and what part should be independent of the tabs. Good lenses exclude everything that is irrelevant to the item you want. Here, a dog lens filters out bird and cat items. Any links to sections that are relative to all categories should not be filtered out, and therefore would be accessible with each tab. Links that are not part of any content category should be displayed separate from the tab set, because they represent an entirely separate mode of user interaction.

3-D Interaction

Figure 9.11 Panning limits the user to movement on one plane, up, down, left, and right like a fly stuck on a window. To access the 3rd dimension, the mouse click, which was once reserved for executing tasks, can represent movement "into≤ the depth of an interface, breaking the limits of the flat space.

Figure 9.14 Immersed in a 3-D environment, navigation requires a unique combination of mouse behaviors. Side-to-side movement makes use of panning, while up and down movement uses tracking. This seemingly contradictory behavior makes physical sense, because the mouse handles like a puppet. Swiveling the mouse to the left to view the left side of a room is like swinging the puppet's head left, while pushing the puppet forward faces it downward. A forward push of the mouse is the right physical action for angling the view downward, even though the cursor will move up as a result.

Eric Eaton Rockport Publishers Peachpit Press Peachpit Press Rockport Publishers DELIBERTE Purchace