With Steve Jobs back at the helm in 2001, Apple forever changed the game in computer user interface (UI) design when it unveiled Mac OS X. As narrated in Inside Steve’s Brain, it was clear that in the process of developing OS X, Jobs put a heavy focus on fully revamping the Mac OS 9 UI due to users’ frustrations (as well as his own) over the operating system’s clunky mechanisms.

Though Apple’s UI/UX approach has undergone big improvements since then, the launch of OS X was an unparalleled moment in computing history as it kickstarted the consumer tech industry’s shift to simplified UI.

Here are three things about OS X that helped usher in a simplified, user-centric design approach to computer technology:

The UI design was inspired by the concept of water droplets.

The UI of OS X was called “Aqua.” Under the close supervision of Jobs, the Apple design team (led by Cordell Ratzlaff) sought to completely overhaul the dominantly gray interface of the classic Mac OS, as well as its contemporaries. Aqua introduced brighter, more saturated control icons and featured droplet-inspired effects and reflections.

UI changes to OS X included a single-window mode

Via Guidebook Gallery

Jobs did not like windows (no pun intended).

Jobs hated the idea of multiple windows spawning whenever the user would open a folder or a file. For OS X, Apple’s design team worked on a single-window mode in which tasks, folders and documents would be displayed in just one window when opened. The Dock—the translucent bar that pops out at the bottom of the screen to accommodate application icons—was also born out of Jobs’ desire to simplify and consolidate application launching.

The Finder window buttons were inspired by traffic light colors.

Back then, even Apple had gray top-corner window buttons. Jobs felt that the plain uniformity of the buttons made it difficult to distinguish what each button does at a glance. He suggested that the buttons should follow the colors of a traffic light, giving users visual clues to their respective functions—red for closing the window, yellow to minimize it, and green to expand it.

The creation of OS X revolutionized UI in its time and continues to influence UX decisions spanning desktop, web, mobile and even wearable interfaces. It wasn’t about turning the existing interface into eye candy; it was about making it simpler for those who are interacting with it—designing OS X for the people, not the system.

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