Update: Wasteland 2's communications team have apologised after incorrectly stating that Wasteland 2 had sold 1.5 million copies. The game has actually grossed $1.5 million, which roughly translates to something in the region of 50,000 sales.

Original story: Wasteland 2, the Kickstarter-funded sequel to a game released 26 years ago, has become an instant hit after selling 1.5 million copies on Steam in its first four days on sale.

It's a dream start for developer inXile Entertainment, the studio that two years ago had pinned its hopes on Kickstarter for funding, and managed to raise some $3 million.

Rough calculations suggest the game has already grossed more than $40 million, perhaps more.

Around 61,000 Kickstarter backers were entitled to claim the game for free via Early Access, meaning not every download adds to the total revenue. However, the final sales figure is likely to be higher than 1.5 million, because inXile has not factored in how many copies were sold through the PC vendor Good Old Games, as well as boxed retail units.

"We are ecstatic that the style of game we love so much has been embraced so well," said inXile Entertainment founder Brian Fargo.

Wasteland 2's strong commercial reception is complemented by a generally positive response from critics. GameSpot's Wasteland 2 review praised it for being a "rich, deep world brought to life exceptionally well".

In April, inXile raised more than $4 million on Kickstarter for its next project, Torment: Tides of Numenera.