Download FREE Portal Game by Tuesday Sept. 20

Tuesday Sept. 20 is the last day that Valve Corp. is giving away FREE downloads of  Portal, one of its best-known game titles. The company says it is doing the giveaway to encourage use of the game to teach principals of physics and critical thinking, but no doubt company brass hope that it will create some lift for its Portal 2 game as well. Caveat: You must first install the company’s Steam game platform client to your PC or Mac. That’s FREE too, but it does require registration. After Sept. 20 you pay $10 for the game.