If you haven't heard of Valheim, well, perhaps just a month ago I'd have understood - now, though, it's blowing up the internet, to a tune of three million sales since it released just a few weeks ago - but for those not in the know, it's a Viking-themed co-op survival game that's become one of the biggest hits on Steam.

And the surprising part is the game is only in early access. Why it's so popular is hard to pin down - it proved very popular with streamers, which may have been part of the influence, and perhaps it's Viking theme is riding on the back of the success of Assassin's Creed Valhalla? It's hard to say. It's clearly popular for a reason though, becoming one of the best selling games on Steam right now. 

According to developer Iron Gate AB, the game has been "purchased by over three million brave Vikings looking to survive the 10th world of the Yggdrasil," which is apparently the equivalent of 74,319 longhouses full of Vikings. Neat statistic. 

The game reached a peak player count of 390,000, which is a huge number, and currently sits as the 7th most popular game on Steam behind the big guns of Minecraft, Rust, CS:GO and Dota 2. It's impressive, either way, but will the success hold? Only time will tell.

What do you think is the secret sauce to Valheim's success? Let us know down in the comments!