Windows Phone features a user interface based on Microsoft's Windows Phone design system, codenamed Metro, and was inspired by the user interface in the Zune HD. The home screen, called the "Start screen", is made up of "Live Tiles", which have been the inspiration for the Windows 8 live tiles. Tiles are links to applications, features, functions and individual items (such as contacts, web pages, applications or media items). Users can add, rearrange, or remove tiles. Tiles are dynamic and update in real time – for example, the tile for an email account would display the number of unread messages or a tile could display a live update of the weather. Since Windows Phone 8, live tiles can also be resized to either a small, medium, or large appearance.