Valve has confirmed that Portal 2 has sold 4 million copies worldwide since launching in April 2011. No breakdown was given between the PC, PS3 and Xbox 360 releases of the game.
Previously, Valve had stated that the original Portal sold over 4 million units, not including sales over Steam. Valve CEO Gabe Newell has indicated that the PC versions of Portal sell better than the console versions.
Valve today also launched the Puzzle Maker for Portal 2. It is designed to be an easy, drag-and-drop way to create test chambers in the game and is part of the free DLC called the Perpetual Testing Initiative.