Please answer the following question: Information:  - The Xbox 360 is a home video game console developed by Microsoft. As the successor to the original Xbox, it is the second console in the Xbox series. The Xbox 360 competed with Sony's PlayStation 3 and Nintendo's Wii as part of the seventh generation of video game consoles. The Xbox 360 was officially unveiled on MTV on May 12, 2005, with detailed launch and game information divulged later that month at the Electronic Entertainment Expo (E3).  - Mobile computing is humancomputer interaction by which a computer is expected to be transported during normal usage, which allows for transmission of data, voice and video. Mobile computing involves mobile communication, mobile hardware, and mobile software. Communication issues include ad hoc networks and infrastructure networks as well as communication properties, protocols, data formats and concrete technologies. Hardware includes mobile devices or device components. Mobile software deals with the characteristics and requirements of mobile applications.  - Valve Corporation (commonly referred to as Valve) is an American video game developer and digital distribution company headquartered in Bellevue, Washington. The company is known for the "Half-Life", "Counter-Strike", "Portal", "Day of Defeat", "Team Fortress", and "Left 4 Dead" series, "Dota 2", and its software distribution platform Steam.  - The user interface (UI), in the industrial design field of humancomputer interaction, is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, whilst the machine simultaneously feeds back information that aids the operators' decision-making process. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls, and process controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology.  - A graphics processing unit (GPU), occasionally called visual processing unit (VPU), is a specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobile phones, personal computers, workstations, and game consoles. Modern GPUs are very efficient at manipulating computer graphics and image processing, and their highly parallel structure makes them more efficient than general-purpose CPUs for algorithms where the processing of large blocks of data is done in parallel. In a personal computer, a GPU can be present on a video card, or it can be embedded on the motherboard orin certain CPUson the CPU die.  - An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require an operating system to function.  - Left 4 Dead is a cooperative first-person shooter video game with survival horror elements, developed by Valve South and published by Valve Corporation. The game uses Valve's proprietary Source engine, and is available for Microsoft Windows, Xbox 360 and OS X. Development on the game was completed on November 13, 2008, and two versions were released digitally: A downloadable digital version, released on November 17, 2008, and a digital retail disc version, with a release date determined by region. The digital retail disc version was released in North America and Australia on November 18, 2008; and in Europe on November 21, 2008.  - Radeon is a brand of computer products, including graphics processing units, random-access memory, RAM disk software, and solid-state drives, produced by Radeon Technologies Group, a division of Advanced Micro Devices. The brand was launched in 2000 by ATI Technologies, which was acquired by AMD in 2006.  - Microsoft Corporation (commonly referred to as Microsoft or MS) is an American multinational technology company headquartered in Redmond, Washington, that develops, manufactures, licenses, supports and sells computer software, consumer electronics and personal computers and services. Its best known software products are the Microsoft Windows line of operating systems, Microsoft Office office suite, and Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface tablet lineup. As of 2016, it was the world's largest software maker by revenue, and one of the world's most valuable companies.  - Microsoft Windows (or simply Windows) is a metafamily of graphical operating systems developed, marketed, and sold by Microsoft. It consists of several families of operating systems, each of which cater to a certain sector of the computing industry with the OS typically associated with IBM PC compatible architecture. Active Windows families include Windows NT, Windows Embedded and Windows Phone; these may encompass subfamilies, e.g. Windows Embedded Compact (Windows CE) or Windows Server. Defunct Windows families include Windows 9x; Windows 10 Mobile is an active product, unrelated to the defunct family Windows Mobile.  - The PlayStation 2 (abbreviated as PS2) is a home video game console that was developed by Sony Computer Entertainment. It is the successor to the PlayStation, and is the second installment in the PlayStation lineup of consoles. It was released on March 4, 2000 in Japan, October 26, 2000 in North America, November 24, 2000 in Europe, and November 17, 2000 in Australia. It competed with Sega's Dreamcast, Microsoft's Xbox, and Nintendo's GameCube in the sixth generation of video game consoles.  - A video game console is an electronic, digital or computer device that outputs a video signal or visual image to display a video game that one or more people can play.  - The original console in the series was the first video game console to ship 100 million units, 9 years and 6 months after its initial launch. Its successor, the PlayStation 2, was released in 2000. The PlayStation 2 is the best-selling home console to date, having reached over 155 million units sold as of December 28, 2012. Sony's next console, the PlayStation 3, was released in 2006 and has sold over 80 million consoles worldwide as of November 2013. Sony's latest console, the PlayStation 4, was released in 2013, selling 1 million consoles in its first 24 hours on sale, becoming the fastest selling console in history.  - IBM PC compatible computers are those similar to the original IBM PC, XT, and AT, able to run the same software and support the same expansion cards as those. Such computers used to be referred to as PC clones, or IBM clones. They duplicate almost exactly all the significant features of the PC architecture, facilitated by IBM's choice of commodity hardware components and various manufacturers' ability to reverse engineer the BIOS firmware using a "clean room design" technique. Columbia Data Products built the first clone of the IBM personal computer by a clean room implementation of its BIOS.  - A video game is an electronic game that involves human or animal interaction with a user interface to generate visual feedback on a video device such as a TV screen or computer monitor. The word "video" in "video game" traditionally referred to a raster display device, but as of the 2000s, it implies any type of display device that can produce two- or three-dimensional images. Some theorists categorize video games as an art form, but this designation is controversial.  - Linux (pronounced or, less frequently) is a Unix-like computer operating system assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. The Free Software Foundation uses the name GNU/Linux to describe the operating system, which has led to some controversy.  - The Wii is a home video game console released by Nintendo on November 19, 2006. As a seventh-generation console, the Wii competed with Microsoft's Xbox 360 and Sony's PlayStation 3. Nintendo states that its console targets a broader demographic than that of the two others. , the Wii leads its generation over PlayStation 3 and Xbox 360 in worldwide sales, with more than 101 million units sold; in December 2009, the console broke the sales record for a single month in the United States.  - A computer monitor or a computer display is an electronic visual display for computers. A monitor usually comprises the display device, circuitry, casing, and power supply. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) or a flat panel LED display, while older monitors used a cathode ray tubes (CRT). It can be connected to the computer via VGA, DVI, HDMI, DisplayPort, Thunderbolt, LVDS (Low-voltage differential signaling) or other proprietary connectors and signals.  - Advanced Micro Devices, Inc. (AMD) is an American multinational semiconductor company based in Sunnyvale, California, United States, that develops computer processors and related technologies for business and consumer markets. While initially it manufactured its own processors, the company became fabless after GlobalFoundries was spun off in 2009. AMD's main products include microprocessors, motherboard chipsets, embedded processors and graphics processors for servers, workstations and personal computers, and embedded systems applications.  - Nvidia Corporation (most commonly referred to as Nvidia, stylized as NVIDIA, nVIDIA or nvidia) is an American technology company based in Santa Clara, California. Nvidia designs graphics processing units (GPUs) for the gaming market, as well as system on a chip units (SOCs) for the mobile computing and automotive market. Nvidia's primary GPU product line, labeled "GeForce", is in direct competition with Advanced Micro Devices' (AMD) "Radeon" products. Nvidia expanded its presence in the gaming industry with its handheld SHIELD Portable, SHIELD Tablet, and SHIELD Android TV.  - The PlayStation 3 (abbreviated as PS3) is a home video game console developed by Sony Computer Entertainment. It is the successor to PlayStation 2, and is part of the PlayStation brand of consoles. It competed with Microsoft's Xbox 360 and Nintendo's Wii as part of the seventh generation of video game consoles. It was first released on November 11, 2006, in Japan, November 17, 2006 in North America, and March 27, 2007 in Europe and Australia.  - Windows 9x is a generic term referring to a series of Microsoft Windows computer operating systems produced from 1995 to 2000, which were based on the Windows 95 kernel and its underlying foundation of MS-DOS, both of which were updated in subsequent versions. This includes all versions of Windows 95 and Windows 98. Windows ME is sometimes included.  - Portal is a 2007 first - person puzzle - platform video game developed by Valve Corporation . The game was released in a bundle package called The Orange Box for Microsoft Windows and Xbox 360 on October 9 , 2007 , and for the PlayStation 3 on December 11 , 2007 . The Windows version of the game is available for download separately through Valve 's content delivery system Steam and was released as a standalone retail product on April 9 , 2008 . A standalone version called Portal : Still Alive was released on the Xbox Live Arcade service on October 22 , 2008 ; this version includes an additional 14 puzzles . An OS X version was released as part of the Mac - compatible Steam platform on May 12 , 2010 . A Linux version was released on Steam as a beta on May 2 , 2013 , and came out of beta on June 24 , 2013 . An Android port for the Nvidia Shield was released on May 12 , 2014 . The game primarily comprises a series of puzzles that must be solved by teleporting the player 's character and simple objects using `` the Aperture Science Handheld Portal Device '' , a device that can create inter-spatial portals between two flat planes . The player - character , Chell , is challenged by an artificial intelligence named GLaDOS ( Genetic Lifeform and Disk Operating System ) to complete each puzzle in the Aperture Science Enrichment Center using the portal gun with the promise of receiving cake when all the puzzles are completed . The game 's unique physics allows momentum to be retained through portals , requiring creative use of portals to maneuver through the test chambers . This gameplay element is based on a similar concept from the game Narbacular Drop ; many of the team members from the DigiPen Institute of Technology who worked on Narbacular Drop were hired by Valve for the creation of Portal . Portal was acclaimed as one of the most original games of 2007 , despite being considered short in length . The game received praise for its unique gameplay and darkly humorous story . It received acclaim for the character...  - GeForce is a brand of graphics processing units (GPUs) designed by Nvidia. , there have been thirteen iterations of the design. The first GeForce products were discrete GPUs designed for add-on graphics boards, intended for the high-margin PC gaming market, and later diversification of the product line covered all tiers of the PC graphics market, ranging from cost-sensitive GPUs integrated on motherboards, to mainstream add-in retail boards. Most recently, GeForce technology has been introduced into Nvidia's line of embedded application processors, designed for electronic handhelds and mobile handsets.  - A personal computer (PC) is a multi-purpose electronic computer whose size, capabilities, and price make it feasible for individual use. PCs are intended to be operated directly by a person using a graphical user interface such as Windows. The versatility of a personal computer is greatly enhanced by the use of peripheral devices such as a keyboard, monitor, printer, mouse, speakers, and an external hard drive.  - The Orange Box is a video game compilation for Microsoft Windows, Xbox 360, PlayStation 3, OS X and Linux. The Windows and Xbox 360 versions were produced and published by Valve Corporation and released on October 10, 2007, as a boxed retail copy. A Windows-only download through Valve's Steam service was released the previous day.  - A system on a chip or system on chip (SoC or SOC) is an integrated circuit (IC) that integrates all components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and often radio-frequency functionsall on a single chip substrate. SoCs are very common in the mobile computing market because of their low power-consumption. A typical application is in the area of embedded systems.    Given the paragraphs above, decide what entity has the relation 'software engine' with 'source'.
A:
portal