Worldwide sales for Portal 2 have reached 3 million units, according to Valve co-founder Gabe Newell.
Newell was speaking at the Games for Learning Institute's Games for Change conference, where according to Gamasutra he revealed the figures to an audience of educators - while discussing how the game could teach lessons about physics.
The figures presumably include Steam sales and suggest the game will eventually outsell the 4 million sales (not including Steam) of the original. Although direct comparisons are difficult given that the first Portal was initially sold only as part of The Orange Box compilation.
Portal 2 has been one of the most critically acclaimed games of the year, with a uniform 95 per cent score for each of its three formats on Metacritic.
The game enjoyed two weeks at number one in the UK, where it kept Warner's Mortal Kombat reboot from the number one slot. In the US though the situation was reversed.
Valve's game was not without controversy though, with many PC users venting their anger at the game being a console port by purposefully marking down the user review scores on Metacritic.