Chucklefish Games confirmed in an interview with Polygon that the indie darling farming sim Stardew Valley had sold over a million copies on Steam, making it one of the highest selling Steam games of 2016 so far. It's consistently topped the sales charts since it's release and right now is sitting just under Ark: Survival of the Fittest and H1Z1: King of the Kill in terms of the most owned game on Steam for 2016. Stardew Valley was released in late February of this year and met with critical acclaim.
Stardew Valley was developed solely by Eric Barone over the course of four years and he continues to update the game. Version 1.07 was released on April 4th and brings heaps of bug fixes as well as improvements to the marriage system, a less harsh punishment for dying in the mines, minor changes to the ways fruit trees work and bringing down the number of pieces of wood required to make coal from 20 to 10. According to MCVUK Barone is in talks with "several companies that are interested in helping me bring Stardew Valley to consoles,” and "Digital download cards may also be released in stores".
Barone has stated in multiple interviews that he learned all of the skills required to make the game himself and just dove in head first. In an interview with PC Gamer Barone was asked if he was expecting the popularity and he said "I wasn't, no. I mean, I thought it would be popular with people who were fans of Harvest Moon or Rune Factory, and I thought that would pretty much be it. I never expected it to have such wide appeal. I mean, I'm super happy about it and I'm blown away by the reaction, but I'm surprised too."