window manager, which limits the screen to showing a single window at a time (Ubuntu Netbook Edition implements a similar system). This is to improve usability on a mobile device with a small screen. Although Maemo is based on Linux and other open source software, some parts of Maemo remain closed source. These include some user-space software, like certain status bar and taskbar applets (including the display brightness applet) and applications, and some system daemons related to connectivity and power management. Software Maemo comes with a number of built-in applications, but additional applications can be installed from a number of sources, including various official and community software repositories, and deb files through either the built-in package manager "Application manager", or the Advanced Packaging Tool and dpkg. Bundled applications include the Mozilla-based MicroB browser, Macromedia Flash player, Gizmo5, and Skype. Notable third-party applications Due in part to the free and open source nature of Linux and Maemo, porting applications to Maemo is a straightforward procedure. Because of this, there are many third-party applications available for the platform. Some applications are original software written specifically for Maemo, while other applications are straight ports of existing Linux programs. Some notable software includes: Media playersMPlayer Internet Claws Mail, Modest, Midori, Firefox for mobile, Opera Mobile Office applications Gnumeric (spreadsheet), Abiword (word processing) Instant Messaging Pidgin VOIP Gizmo5, Skype Games The Battle for Wesnoth, Wormux, Doom, Angry Birds Others FBReader (e-book reader), GPE (OpenSync compatible PIM), rdesktop (RDP remote access), Rhapsody (subscription music, US only), ScummVM (game emulator), Free42 (HP-42S calculator emulator), Monsoon HAVA (TV viewer and controller), Navit (GPS navigation software), Vagalume (Last.FM player), VNC Fremantle StarsApplications developed by the community and supported by Nokia as Fremantle Stars will be part of Maemo 5. Notable applications include ScummVM (game, includes Beneath a Steel Sky) and Fennec (web browser). Debian The complete ARM Debian distribution can be installed as a Maemo application, making thousands of software packages available (including OpenOffice.org, Mozilla Firefox, Java, the GNOME and LXDE desktops, etc.). Debian ARM packages can also be used if they are modified with the maemo-optify tool. The ability to run largely unmodified linux packages sets Maemo apart from other Linux-based mobile operating systems, such as Android and webOS. Media support Other media types, such as the audio format .OGG, can be added with the use of community plug-ins. Video MPEG-1, MPEG-4 ASP (H.263), RealVideo, AVI, 3GP Audio/playlists