Valve's announced that sales of the original Portal sit at almost 4 million units, and that's not including one or two copies that may have been sold via Steam.
Portal had humble beginnings, starting its digital life as a DigiPen Institute of Technology student project titled Narbacular Drop. After it won the Independent Game Festival's Student Showcase Award in 2006, the game and its student creators were signed up by Valve.
Originally released as an unassuming part of Valve's super-value blockbuster The Orange Box, Portal was gifted a standalone release in 2008. Add all these sales together and you reach that magic almost 4m unit milestone, in addition to the copies sold via Steam - which are unknown as Valve doesn't release Steam sales figures.
Portal 2 released on PC on Tuesday 19 April via Steam. High street retailer GAME has also started selling the PC version in store today. It releases on PS3 and 360 tomorrow, April 21.
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