Portal Free Until September 20

Pleased with the idea of educators using Portal to teach students mathematics, Valve has decided to offer the game up for free. Of course, this is for a limited time, meaning you’d better act quickly. September twentieth is the cut-off day to get this great deal on a very well-loved puzzler.

This free download is limited to your computer type of choice: PC or Mac.

Enjoy. Sorry we don’t have any cake for you.