Metro (design language) - Wikipedia, the free encyclopedia
Animation plays a large part, with transitions, and user interactions such as presses or swipes recommended to always be acknowledged by some form of natural animation or motion. This is intended to give the user the impression that the UI is "alive" and responsive, with "an added sense of depth."
Internally, Microsoft has compiled a list of principles as core to the design language.
Close to the official launch date of the product (Oct 25, 2012), more developers and Microsoft partners started working on creating new Metro applications, and many websites with resources related to this topic have been created, as well as the Microsoft's UX guidelines for Windows Store Apps.