In October 2013, Chrome's app was changed to mimic the desktop environment used by Chrome OS. Development of the Firefox app for Windows 8 has since been cancelled, citing a lack of user adoption for the beta versions. Windows 8 introduces significant changes to the operating system's user interface, many of which are aimed at improving its experience on tablet computers and other touchscreen devices. The new user interface is based on Microsoft's Metro design language and uses a Start screen similar to that of Windows Phone 7 as the primary means of launching applications. The Start screen displays a customizable array of tiles linking to various apps and desktop programs, some of which can display constantly updated information and content through "live tiles". As a form of multi-tasking, apps can be snapped to the side of a screen. Alongside the traditional Control Panel, a new simplified and touch-optimized settings app known as "PC Settings" is used for basic configuration and user settings. It does not include many of the advanced options still accessible from the normal Control Panel. A vertical toolbar known as the charms (accessed by swiping from the right edge of a touchscreen, swiping from the right edge of a trackpad, or pointing the cursor at hotspots in the right corners of a screen) provides access to system and app-related functions, such as search, sharing, device management, settings, and a Start button. The traditional desktop environment for running desktop applications is accessed via a tile on the Start screen. The Start button on the taskbar from previous versions of Windows has been converted into a hotspot in the lower-left corner of the screen, which displays a large tooltip displaying a thumbnail of the Start screen. However, Windows 8.1 added the start button back to the taskbar after many complaints. Swiping from the left edge of a touchscreen or clicking in the top-left corner of the screen allows one to switch between apps and Desktop. Pointing the cursor in the top-left corner of the screen and moving down reveals a thumbnail list of active apps. Aside from the removal of the Start button and the replacement of the Aero Glass theme with a flatter and solid-colored design, the desktop interface on Windows 8 is similar to that of Windows 7. Several notable features have been removed in Windows 8; support for playing DVD-Video was removed from Windows Media Player due to the cost of licensing the necessary decoders (especially for devices which do not include optical disc drives at all) and the prevalence of online streaming services. For the same reasons, Windows Media Center is not included by default on Windows 8, but Windows Media Center and DVD playback support can be purchased in the "Pro Pack" (which upgrades the system to Windows 8 Pro) or "Media Center Pack" add-on for Windows 8 Pro.