Mojang 2012, Mojang was co-developing a video game codenamed "Rex Kwon Do" alongside an undisclosed developer. Before the title had reached a significant stage of development, Mojang cancelled the collaboration, due to their lack of involvement and influence on the project. In March 2012, Persson revealed that he would be designing a space sandbox game. Although Mojang teased with an April Fools' Day website based around "Mars Effect" (citing the Bethesda lawsuit), it was confirmed that the game was indeed in development, albeit with a different name. On 4 April, Mojang revealed the game's title to be "0x10", set in the
Minecraft and has never been commercially advertised except through word of mouth, and various unpaid references in popular media such as the "Penny Arcade" webcomic. By April 2011, Persson estimated that "Minecraft" had made €23 million (US$33 million) in revenue, with 800,000 sales of the alpha version of the game, and over 1 million sales of the beta version. In November 2011, prior to the game's full release, "Minecraft" beta surpassed 16 million registered users and 4 million purchases. By March 2012, "Minecraft" had become the 6th best-selling PC game of all time. , the game has sold 17 million copies