To typical users, a software product is defined largely by the features its interface exposes. There's far more to an operating system than the UI alone, though, and Microsoft doesn't expect to nail down many user-visible aspects of Windows Vista until the release of Beta 2. Still, Beta 1 hints at how Microsoft is approaching the UI challenge, though much of what we describe here is bound to change by the time Windows Vista ships. Windows Vista's new look-and-feel is known as "Aero." On suitably equipped machines, Aero will exploit 3D graphics accelerators to implement "Glass" display effects. At this point, at least, the venerable shell metaphor of a desktop with overlapping windows hasn't changed, but Aero Glass uses subtle visual cues to make the experience much more convincing and seamless—we'd dare say even a bit Mac-like. Window and dialog borders are partially transparent, blurring content behind them and casting drop shadows to enhance the sense of depth. They appear and disappear using understated zooming and fading effects. Buttons and controls have a gel-like look and light up in natural-looking ways.