In case you haven’t heard, Portal is now available free, until September 20! And this is no gimmick or trial version; it’s the real thing. The deal is part of Valve’s “Learn With Portals” initiative, which showcases how the game can be used as a teaching tool for physics and alternate-reality engineering.

I’ve been hearing and repeating awesome things about this game ever since it came out in 2007, and now I have no excuse left not to play it. Same goes for anyone else who hasn’t already experienced the goodness of cake Portal. Plus, in addition to getting a cool game, you’re helping support a company that believes in not only physics education, but also DRM done right — what’s not to like? So head over to the download page and start portaling today!