Appearance Manager
The Mac OS 8 component that drew windows, buttons and menus centrally and gave the Mac its grey, bevelled Platinum look.
Before 1997 every Mac program drew much of its own interface, and the look was essentially the black-and-white one from 1984 with a little colour on top. Appearance Manager, one of the few pieces salvaged from the cancelled Copland project, moved the drawing into the system. Mac OS 8 gave everything the same grey three-dimensional finish, called Platinum, and programs using the new interface calls got it for free.
The promise was themes. Betas of Mac OS 8.5 shipped three more — Hi-Tech, Gizmo and Drawing Board — but all were pulled before the 1998 release and only Platinum made it out. Anyone wanting a different look had to turn to third-party tools such as Kaleidoscope. Mac OS X replaced the lot with Aqua, and Platinum became the classic Mac's final face.