The S4 was originally released with Android 4.2.2 and Samsung’s TouchWiz Nature UX 2 interface. Head tracking features have been extended on the S4; the new "Smart Scroll" feature can be used to scroll while looking at the screen by slightly tilting head or phone forward or backward, [31] and "Smart Pause" allows the video player to pause videos if the user is not looking at the screen. "Air View" and "Air Gestures" implement gestures and other functionality(such as previewing images or messages) by holding or swiping a hand or finger slightly above the screen, similarly to Samsung’s Galaxy Note series, and adds a feature known as "Quick Glance", which uses the proximity sensor to wake the phone so it can display notifications. The "Group Play" feature allows ad hoc sharing of files between Galaxy phones, along with multiplayer games and music streaming between S4 phones. The S4 also introduces Knox in the Android 4.3 update, a suite of features which implements a sandbox for enterprise environments that can co-exist with a user’s "personal" data. Knox incorporates use of the ARM TrustZone extensions and security enhancements to the Android platform