Unknown Worlds was formed in May 2001 by Charlie Cleveland and began life as a group of developers responsible for the development of the high-profile free mod for Half-Life, Natural Selection. The success of Natural Selection convinced Cleveland to start work on a commercial sequel to the game: Natural Selection 2. Soon after Cleveland founded Unknown Worlds Entertainment as a commercial computer games studio. Although the casual games market is not the intended direction of Unknown Worlds, Zen of Sudoku, a casual puzzle computer game based on the popular logic puzzleSudoku, was created in November 2006 in order to generate revenue towards funding the development of Natural Selection 2. Charlie Cleveland, one of the developers of Unknown Worlds Entertainment, cited casual games development as a "last option" for funding this sequel, having been unwilling to sacrifice control of the company to external investors. In October 2006, Max McGuire became the studio's co-founder, having previously worked at Iron Lore Entertainment as Lead Engine Programmer. McGuire became the Technical Director of UWE and development of Natural Selection 2 began in earnest. Max and Charlie then attracted a group of angel investors including Richard Kain, Matthew Le Merle, Ira Rothken and Colin Wiel to back the company after a meeting at GDC in San Francisco. A year later, Unknown Worlds released Decoda as a commercial debugger for the Lua programming language. This application was created to aid with development of Natural Selection 2, whose game code was largely being written in Lua. Later on in development of Natural Selection 2, the studio announced it had changed engine from the Source engine to their own proprietary engine developed in-house. After consulting their fanbase on a possible name for their new engine, it was finally named the Evolution engine. Later, it transpired that the name Evolution was already taken and Spark was chosen as the name for the engine. In June 2008, Cory Strader was hired as art director. Strader had been a previous key member of the development team for Natural Selection. In May 2009, Unknown Worlds began taking pre-orders for standard and special edition versions of Natural Selection 2. Natural Selection 2 was released on 31 October 2012. In February 2013, Unknown Worlds released the source code for Decoda onto GitHub.
