It doesn’t matter who you are””young or old, big or small, Fanboy, Trekkie, or Twi–hard — we all love free stuff.

That’s why you’ll be elated to hear that the insanely popular puzzle game from Valve, Portal, is being offered for free on Steam until tomorrow, September 20, 2011. The game is available for both Mac and Windows, and you can find out where to score it by heading below now.

Portal sees you in a strange place, trying to escape using a gun that allows you to shoot portals into the walls””one to enter, the other to exit out of. Using this tool, you’ll have to navigate some difficult areas to get to the next area on a mission to escape wherever it is you are.

The game has since seen a sequel get made as well as the release of the ultra–popular live–action short film recently made by Totally Rad Show host Dan Trachtenberg.

This special offer is through Learn With Portals, an education initiative using games like Portal to help keep learning fun and interesting. If you want to get your hands on the game for free, you can head to the Steam site now to download it.

And again, this ends tomorrow…so don’t wait!