Kerbal Space Program (commonly abbreviated as KSP) is a space flight simulator developed by Squad for Microsoft Windows, OS X, Linux, PlayStation 4, Xbox One, and Wii U. In the game, players control a space program, build and fly spacecraft under physics simulation, and explore celestial bodies with characters called kerbals. The first publicly available version was released on the official Kerbal Space Program store on June 24, 2011. The game also became available on Steam's early access program on March 20, 2013. The game was officially released out of beta on April 27, 2015. The game has large support for game mods and a large community to create them, which developed shortly after the game's initial release. Notable members of the space industry have taken an interest in the game, including NASA and Elon Musk of SpaceX.