When the Mac came out Apple did something new for personal computers, they published a human interface guidelines document, a thick book, written in easy to understand English, but it was also technical. It was a guide for developers showing how to make Macintosh software that was as usable as possible for everyone. And while it made it more difficult for developers at first, over time it made it easier, because many of the design questions were answered. It was good for business too, because people could use more software if there was a consistency to its design.