Fearon was sent a copy of Half-Life by Valve prior to its official release, and while playing it, he toyed with the game's code, 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 phone-line modems.
Fearon was given an early copy of Half-Life by Valve ahead of its release, and while playing it, he played around with the game's code, discovering how to bring enemy creatures into multiplayer maps. Initially, Fearon's work had been done before Valve released the software development kit for Half-Life, so he had to build his modification on top of the existing Half-Life package and work with multiplayer over slower internet connections.