Minecraft led to Persson becoming one of "Forbes" "World's Billionaires". "Minecraft"s music and sound effects were produced by German musician Daniel Rosenfeld, better known as C418. The background music in "Minecraft" is instrumental ambient music. On 4 March 2011, Rosenfeld released a soundtrack, titled "Minecraft – Volume Alpha"; it includes most of the tracks featured in "Minecraft", as well as other music not featured in the game. The video game blog Kotaku chose the music in "Minecraft" as one of the best video game soundtracks of 2011. On 9 November 2013, Rosenfeld released the second official soundtrack, titled "Minecraft – Volume
Minecraft meters above in-game sea level. "Minecraft" has also been used in educational settings. In 2011, an educational organization named MinecraftEdu was formed with the goal of introducing "Minecraft" into schools. The group works with Mojang to make the game affordable and accessible to schools. In September 2012, MinecraftEdu said that approximately 250,000 students around the world have access to "Minecraft" through the company. A wide variety of educational activities involving the game have been developed to teach students various subjects, including history, language arts and science. For an example, one teacher built a world consisting of various historical landmarks for