The games currently sitting in Steam's top sellers list have familiar names: Fallout 4, Tom Clancy's The Division and Far Cry Primal all hold top 10 spots. But one game, Stardew Valley, is less well-known. Yet the indie role-playing game, which arrived on the Steam marketplace on Feb. 26, is tucked directly beneath Fallout 4's season pass on the sales chart.

But what even is Stardew Valley? And how has it already made it onto the front page of Steam?

Stardew Valley is a farming simulator, a pixelated throwback to the Harvest Moon series' early days. From the description on its store listing, the game has a similar plot to the popular agricultural RPG: The player inherits their grandfather's farm, a plot of land they must learn how to care for in order to help revitalize the community of Stardew Valley.

There's fishing, mining, cooking and crafting available in the game, as well as player and house customization options. Also offered are 10 suitable guys and girls whom the player can court and eventually marry.

A cursory glance over its Steam page paints Stardew Valley as simply a PC version of the Harvest Moon games. But while the public at-large may be surprised by the relative unknown's sales success, Stardew Valley has had devoted fans since prior to its Friday launch, largely because of how the game differs from its obvious influence.

Unlike Harvest Moon, Stardew Valley allows players to engage in same-sex relationships. It also is more open-ended than Natsume and Marvelous Interactive's franchise: Players have increased control over how they design their farms, what kinds of animals and crops they raise, more dynamic non-playable characters and randomly generated caves. Co-op multiplayer is also planned for a future update, with new features and patches continuing to be added to the game after release.

Stardew Valley has been a mainstay on the popular Games subreddit for months ahead of its debut, due in large part to its developer's community presence. Reddit user Concerned Ape, also known as Eric Barone, has been an active member of the game's burgeoning fandom, answering questions and offering updates on Reddit during the development process.

Barone also blogged about his work on the game's website since the very beginning — dating back almost four years. He's steadily added more content to Stardew Valley, which he launched on Steam Greenlight in September 2012, all of which he detailed for fans online. Certain fans even got to test the game's beta, contributing ideas and suggestions to Barone directly.

In an update from April 2015, Barone — who crafted the game entirely on his own — discussed his commitment to only launching the game when it was a complete, finished project.

"I've been working on Stardew for years and I want it to be released as much as anyone," he wrote. "However, I'm not willing to do that until the game is not only complete, but also in a state I'm happy with. It simply could not be released in its current form... It's not a finished game yet. It's tantalizingly close to being a finished game, but it's also a huge project and I'm just one guy."

Even without a release date, people who picked up the game from Steam Greenlight were already wild about it. The game's publisher, Chucklefish, showed off gameplay in hourlong streams, like below, something fans are now doing themselves.

At the end of January, Barone finally announced on the blog that the game would arrive in full for $14.99 on Steam on Feb. 26. The reception on both Steam and Reddit has already been highly favorable; the game has an "overwhelmingly positive" rating on Valve's platform, and a subreddit dedicated to Stardew Valley has over 6,000 subscribers.

Stardew Valley remains a work in progress — the game's 1.03 build launched on Steam today — but its popularity has already been solidified. As a Harvest Moon-like on a platform lacking farming sims, the game has tapped into a niche and already made its mark.