You wouldn't know, turning into this nondescript street in Stockholm and padding up the stone steps to Minecraft HQ, that anything special was being made up here. The truth only becomes clear when you step through the door and discover the endless shelves filled with awards (including a Bafta) and the vast boxes of Minecraft merchandise piled in every corner. This is where they make what many regard as a digital version of Lego: a game that's been downloaded more than 100m times on PCs, consoles and smartphones since its launch in 2009. If you have children aged between six and 16, the chances are they're hooked on this strange, blocky pursuit. And the chances are you've asked yourself: why? To truly understand the appeal of Minecraft, you need to understand the studio behind it.