Please answer the following question: Information:  - 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.  - 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.  - Eclipse is a mod for the video game Half - Life 2 . It is a fantasy - themed action - adventure viewed in third - person . Eclipse was developed by CelTech Studios , a group of students from The Guildhall at SMU and released June 17 , 2005 .  - Half-Life 2 (stylized as HLF-LIFE) is a first-person shooter video game developed and published by Valve Corporation. The sequel to 1998's "Half-Life", it was released in November 2004, following a five-year, $40 million development phase, during which a substantial part of the project was leaked and distributed on the Internet. The game was developed alongside Valve's Steam software and the Source engine.  - 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.    Given the paragraphs above, decide what entity has the relation 'software engine' with 'source'.
Answer:
eclipse