The game was originally created and released by Daniel Fearon; Fearon at the time was one of the maintainers of the "Half-Life" fan website "Atomic Half-Life" created in anticipation of the game's release. Fearon was sent a copy of "Half-Life" by Valve prior to its official release, and as he started playing it, he had also begun toying with its programming, figuring out how to spawn enemy creatures in multiplayer maps. Fearon's work had initially been done before Valve released the software development kit for "Half-Life", requiring him to craft the modification atop the existing "Half-Life" distribution and to work with multiplayer over slower Internet connections, such as through phone-line modems. Fearon initially developed a single map that could be played cooperatively, and later a second version with two maps. The first public version of "Sven Co-op" was released on January 19, 1999, about 3 months after the release of "Half-Life". He used the name "Sven Co-op" to reflect his online handle, "Sven Viking".