Roblox is an online game platform and game creation system that allows users to program games and play games created by other users. Founded by David Baszucki and Erik Cassel in 2004 and officially released in 2006, the platform hosts user-created games in many genres, such as racing games, role-playing games, simulations and obstacle courses, coded in the programming language Lua. Roblox is free-to-play, with in-game purchases available through a virtual currency called "Robux". As of August 2019, Roblox has over 100 million monthly active users. Roblox has received generally positive reviews from critics.