Ragnarok Online is a massive multiplayer online role-playing game created by Gravity based on the manhwa Ragnarok by Lee Myung-jin. It was released in South Korea on 31 August 2002 for Microsoft Windows. The game has spawned an animated series, Ragnarok the Animation, and a sequel game, Ragnarok Online 2: Legend of the Second. Player characters exist in a world with a player environment that gradually changes with the passage of time. Major changes in the features and history of the world take place as episodes in the RO timeline.