Simutronics

Simutronics is an American online games company whose products include GemStone IV and DragonRealms. It was founded in 1987 by David Whatley, with husband and wife Tom & Susan Zelinski. The company is located in St. Louis, Missouri. It became part of the Stillfront Group in 2016.

The company's flagship product is the text based game, GemStone IV, which went live in November 2003, with predecessor games running back to 1988. GemStone was originally accessed through General Electric's internet service provider GEnie, later becoming accessible through AOL, Prodigy, and CompuServe before Simutronics finally moved all their games to their own domain in 1997.

Multiplayer online games

 * GemStone IV, Simutronics' flagship product, a text-based multiplayer fantasy game, which has seen over one million users over the years. It is the longest-lived commercial MUD game, followed by Avalon:_The_Legend_Lives.
 * DragonRealms, set in the same fantasy world as GemStone, only at a later place in time. Additional versions include DragonRealms Platinum, and DragonRealms: Fallen.
 * Modus Operandi, a MUD set on a fictional Caribbean island, originally designed to encourage mystery-based roleplay, which closed on November 2, 2015.
 * Alliance of Heroes, formerly Hercules & Xena: Alliance of Heroes, this adventure-based MUD was set in the universe of the TV shows Hercules: The Legendary Journeys & Xena: Warrior Princess. In later years the game changed its license, and removed specific Hercules & Xena trademarks, and ran as a retooled "tongue in cheek" mythology MUD until its closure on November 2, 2015.
 * CyberStrike, also known as CyberStrike Classic, a graphical futuristic ship combat game. It won the first ever "Online Game of the Year" award from Computer Gaming World magazine in 1993.
 * Orb Wars, (no longer available) an early graphical game involving team combat between wizards
 * GemStone ][ (no longer available), an early commercial text-based multiplayer fantasy game
 * GemStone III (morphed into GemStone IV), a text-based multiplayer game which was originally based on the Rolemaster rules from Iron Crown Enterprises
 * CyberStrike 2, a sequel to CyberStrike, released in 1998
 * Hero's Journey, an unreleased graphical MMORPG utilizing the "HeroEngine", an MMO engine developed by Simutronics for the game.  The game had been in development since the late 1990s, but its release date was pushed back several times and in March 2009, all remaining developers and game masters assigned to Hero's Journey were laid off or reassigned. Hero's Journey as well as the engine behind it was sold off due to the economic decline in 2008-2009.
 * Dragons of Elanthia (currently in Beta), a multiplayer third-person shooter in which players select different dragons and riders, each with unique abilities, to fight each other. The game uses the Unity game engine. After a failed kickstarter development was halted.

Mobile games

 * Tiny Heroes, a tower defense game for iPhone and iPad, released in 2011
 * One Epic Knight, an endless runner game, released in 2012 for iOS devices and in 2013 for Android
 * Lara Croft: Relic Run, developed by Simutronics and published by Square Enix on Android, Windows Phone, and iOS in 2015.

Interactive fiction engine
Simutronics' products GemStone IV, DragonRealms, Modus Operandi, and Alliance of Heroes are text-based multiplayer games built on a proprietary Interactive Fiction Engine (IFE) written in the C programming language. The IFE is responsible for managing the server's memory, interacting with the game's database, and communicating with the clients. It also includes an interpreter for the proprietary GemStone Scripting Language (GSL), a relatively simple language which abstracts away most of the complex details that the IFE handles. Originally, many core game commands (such as those relating to movement and inventory management) were implemented directly by the IFE. Over time, most of those have been migrated to GSL to allow for easier modification.

HeroEngine
HeroEngine is a 3D game engine and server technology platform developed specifically for building MMO-style games, based around a system similar to the IFE using the Hero Script Language (HSL). Originally developed for the company's own game Hero's Journey - which never made it to the testing stage - the engine has since been licensed by other companies. Simutronics sold the HeroEngine to Idea Fabrik, Plc. on August 5, 2010.