Video game modifications, or mods, offer creative gamers a way to bring their own genius to preexisting video games. They can be used to create original characters or entirely new levels and scenarios, which can then be shared over the Internet with other gamers. Fortunately, you don't have to be an expert computer programmer to create your own mod. A variety of programs and tutorials are available on the Internet to help you get started. Because of its popularity, most of the available tools apply specifically to the game Half-Life, created by Valve Software.