Honoring its unexpected promise , Mojang has made Cobalt—it's first third-party published game—available for sale today. Head to www.playcobalt.com to take a look. Like Minecraft, the side-scrolling, 2D, multiplayer platformer has been released as an alpha that'll be updated over time. If you have a Minecraft account, you can use it to buy and access Cobalt.
"The full game will sell for $26 and it will be discounted 50% to $13 during Alpha. The Beta will have a 25% discount tag," states Mojang's release. Here's a breakdown of the different content that'll be included in the alpha, beta, and final versions of the game, along with an FAQ.