Valve says Portal 2 is "way worse" than Half-Life 2 in terms of giving away spoilers.
Speaking to our E3 minion in Los Angeles, Valve boss Gabe Newell said the problem with showing off Portal at the trade show is that once you know the solution to a puzzle you can just run straight through the final game.
"One of the challenges of showing this game here is that it's difficult to give people an idea of what kind of game it is," he said. "The level of spoiling with this game is so hard - way worse than Half-Life 2."
He added that for that reason, "we probably won't have a demo."
Valve revealed at Sony's E3 press conference earlier this week that Portal 2 will be coming to PS3 along with its Steamworks development suite.