Original Apple Mouse

The first approach was to pair a freely-rolling ball with a optoelectronic system to track the ball’s movement and minimize the affect the friction on the ball, transmitting information about its movements to the cursor on the screen.

The Xerox mouse relied on a small ball, forced down against the tabletop, whose motion was tracked by an elaborate system of mechanical switches, with an array of ball bearings supporting the roller ball. But this caused too much friction on the top of the ball, and a lot of dust and grime collected by the mouse, causing the mouse to skip. The main challenges were to solve the problems of the ball bearing, the encoders, and dirt.

The team got inspiration from the Atari arcade machine. The Atari machine differed from the Xerox mouse in a few key ways. For one, its trackball wasn't forced up or down. Instead, it just floated. Moreover, it resulted in less friction and fewer parts. That was one key insight. The Atari machine also used optics to track the trackball's movement, relying on interrupted beams of light instead of mechanical switches. By borrowing this concept, this further streamlined the internal components.

Other insights came when the team watched balls roll off a table in their office, whose floor wasn’t quite level. “They’d roll off onto the floor, following the slant of the table, and that’s exactly what I want it to do: I want it to roll without slipping." By putting fingers around a ball like a little cage, the ball was no longer being pushed on as a bearing support, it was actually free to roll, and the encoders would barely need to touch it to get the information about where it was moving.

The Hovey-Kelley designers now spent a lot of time on that one button, thinking about its aesthetics and ergonomics, which would play a critical role in defining the feel of the device and affect the character of the Lisa and Macintosh user interface. The size of the body, weight of the ball, flexibility of the cord, and detailing of the sides of the case all subtly affected how solid, smooth, and precise the mouse would feel, but the button was something users would touch dozens of times during a session, as they opened documents, chose commands from the menu bar, positioned the cursor, and cut and pasted.

Getting the button right would mean getting the mouse right. What was right? The answer was defined in part by ergonomics. A user’s finger would rest on the mouse while he or she was positioning the cursor, so the button couldn’t be too sensitive. But the mouse also had to give a clear sense of interaction. A click was added to provide audible feedback when the button was pushed, confirming the response on the screen or signalling a problem if nothing happened, and the click was coordinated with a tactile signal, a clicky feeling.

This effort to get the button right was a matter of realizing what Jim Sachs called “the Zen of the product,” the hard-to-describe yet crucial qualities that would define the experience users had with the mouse. Designing a rugged detector and encoding system, a rib cage to hold the electronics and mechanical parts together, and a removable cleaning ring were all necessary, but no one would actually want to use the thing unless they also paid careful attention to its ergonomics and aesthetics. This willingness to obsess over the aesthetics and details of the mouse was something that significantly contributed to the success of the product.

One reason the Apple user interface was so outstanding was that the mouse was developed together with the rest of the interface, yielding a “very tight interaction” between input device and computer. Consequently, the mouse would lag behind, or it would stutter, allowing users to be better able to make a precision alignment.

Apple’s mouse project turned out to be a textbook example of “rapid prototyping” - building something quickly to try out one’s ideas about it, relying more on models and materials than on formal specifications or user tests. The ultimate purpose of rapid prototyping, a style of innovation taught at the Stanford Product Design Program, was to encourage ingenuity. As Kelley put it, “In order to have breakthrough ideas, you have to have a lot of ideas, all different from one another.”

The ultimate users of technological designs typically notice bad design more easily than good design; it is the peculiar nature of a good user interface to be all but invisible. The fact that the mouse was non-obtrusive and natural is the result of a lot of work. Few users ever notice the heft of the cord, or the feel of the button, or the silence of the ball as a mouse moves across the desk. And they’re not supposed to. The mouse is one of those technologies whose invisibility is a measure of their success, the product of a process whose final act is to erase all traces of itself, leaving behind something that seems only natural in the arrangement of its parts and operation. Apple was willing to obsess over these small details, and that is what they had become famous for.

In summary, IDEO made use of inspiration from other sources, took concepts from real world applications and applied ergonomics to deliver a reliable, simplified, inexpensive product that delivered a comfortable and smooth experience.