FreeSpace 2 is a 1999 space combat simulation computer game developed by Volition as the sequel to Descent: FreeSpace – The Great War. It was completed ahead of schedule in less than a year, and released to very positive reviews, but the game became a commercial failure, and was described by certain critics as one of 1999's most unfairly overlooked titles. The game continues on the story from Descent: FreeSpace, once again thrusting the player into the role of a pilot fighting against the mysterious aliens, the Shivans. While defending the human race and its alien Vasudan allies, the player also gets involved in putting down a rebellion. The game features large numbers of fighters alongside gigantic capital ships in a battlefield fraught with beams, shells and missiles in detailed star systems and nebulae. Free multiplayer games were available via Parallax Online which also ranked players by their statistics. A persistent galaxy was also available as SquadWar for players to fight with each other over territories. In 2002, Volition released the source code for the game engine under a non-commercial license. This code became the core of the FreeSpace 2 Source Code Project, which continuously improves it and enables new features. In cooperation with the FreeSpace Upgrade Project the game's graphics are kept up to date. The improved game engine is also used by various mod projects, for example The Babylon Project and Diaspora which are based on the science fiction series Babylon 5 and Battlestar Galactica respectively. Gameplay FreeSpace 2s gameplay involves the player piloting a starfighter using mounted weapons to destroy enemy starfighters, performing reconnaissance behind enemy lines, or escorting other starships. Its flight model is based on a looser interpretation of space physics instead of realistic Newtonian physics. Hence, the ships are weightless and feel more responsive, though they require constant application of engine power to move. The result is that the game plays more like a "WWII dogfight simulator" unaffected by gravity. Although joysticks are the recommended controller for this game, the mouse is a viable alternative. Single player mode is executed in the form of a campaign, which follows a story as a linear sequence of missions are executed. The pre-mission briefing stage is where the player gets information on the background and objectives, and selects the ship and weapons. The choices of ships and weapons increase as the player proceeds further along the campaign.