Dungeons & Dragons is a fantasy tabletop role-playing game originally designed by Gary Gygax and Dave Arneson, and first published in 1974 by Tactical Studies Rules, Inc.. The game has been published by Wizards of the Coast since 1997. It was derived from miniature wargames with a variation of the Chainmail game serving as the initial rule system. D&D's publication is widely regarded as the beginning of modern role-playing games and the role-playing game industry. D&D departs from traditional wargaming and assigns each player a specific character to play instead of a military formation. These characters embark upon imaginary adventures within a fantasy setting. A Dungeon Master serves as the game's referee and storyteller, while also maintaining the setting in which the adventures occur and playing the role of the inhabitants. The characters form a party that interacts with the setting's inhabitants. Together they solve dilemmas, engage in battles and gather treasure and knowledge. In the process the characters earn experience points to become increasingly powerful over a series of sessions. The early success of Dungeons & Dragons led to a proliferation of similar game systems. Despite this competition, D&D remains the market leader in the role-playing game industry. In 1977, the game was split into two branches: the relatively rules-light game system of Dungeons & Dragons and the more structured, rules-heavy game system of Advanced Dungeons & Dragons. AD&D 2nd Edition was published in 1989. In 2000, the original line of the game was discontinued and the AD&D version was renamed Dungeons & Dragons with the release of its 3rd edition with a new system. These rules formed the basis of the d20 System which is available under the Open Game License for use by other publishers. Dungeons & Dragons version 3.5 was released in June 2003, with a 4th edition in June 2008.