"Portal was a test bed... Portal 2 is a game," Valve has told US mag Game Informer.
Speaking in the mag's latest issue, which exposes the first Portal 2 details, Valve's VP of marketing and all-round friendly man, Doug Lombardi says the success of the first game has allowed it to go further in number two.
"Portal was so short because it was a trial," Lombardi told the mag. "We paired it with [Half-Life 2] Episode 2 and Team Fortress 2, which were recognisable and safe. Then we had this Portal thing, and we had no idea if people would dig it, even though we thought it was a cool idea.
"So it was put out their safely in The Orange Box, and the result came back wilder than we could have ever imagined," he added, referencing the huge cult following that followed Portal's 2007 release.
"We knew we had to double down and give them more. Portal was a test bed. Portal 2 is a game."
According to the GI piece, Valve's investing more time, more capital (the team's been bumped from 8 to 28, it says) and more risk into the stand alone, full price retail release.