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Where does light come from? ..........................................................

As long as we tackle relativity theory in this book, why not also explore the

origin of light itself or at least the psychophysics of light sources?

Microsoft darkens the color used for the left and top borders of its inset

design (for depressed, clicked buttons in Word, for example), and leaves the

right and bottom frame sides light. Buttons just sitting there without being

clicked are outset and the left and top borders are lighter than the right and

bottom borders. Why?

In Windows graphic style (menus, buttons, window frames, and so on), the

light is always assumed to be coming from the upper-left corner of the screen.

Therefore, a visually protrudingobject like a button picks up highlights along

its top and left sides. Shadows fall along the right and bottom of the object.

However, if the object is supposed to be sinking into the background — such

as an inset frame or a clicked button — the process is reversed and the top

and left sides are darkened.

This effect actually works pretty much the same way in the real world: When

you’re reading outdoors, if you’re like most people, you maneuver your lounge

chair or towel until the sun shines from your left side — and, of course, the

sun is above.

Take a look at your work area. Most people prefer to put lamps to the left

of and above their desk or reading chair. As an experiment, turn this book

Figure 6-8:
Adjust the
border-
width
property to
get different
effects, like
this simple
matting
effect.

Chapter 6: Managing Details in Style Sheets 121