Original Portal Free on Steam for Limited Time

Valve has made the original Portal game on Steam free until early next week.

Are you one of the few who still hasn't purchased the original Portal PC game? Then today's your lucky day, as Valve is making the hit puzzler free for every PC and Mac gamer to download and play until September 20, 2011. There's no catch that we can tell -- no indication that the game will lock you out at the stroke of midnight. It seems to be yours to keep forever and ever.

The free Portal giveaway is actually part of a promotion stemming from Valve's Learn with Portals games education initiative. As Valve states on the website, one of the biggest challenges in teaching science, technology, engineering, and math is capturing the students’ imaginations long enough for them to see all of the possibilities that lie ahead.

"When we heard the buzz surrounding the new role video games are playing in education, we had to throw our hat in the ring," the company said. "It's eye-opening to see how video games can be used in amazing and unexpected ways to help educate our next generation."

That's where Portal comes in, a tool that students (and everyone else) can download and play for free.

"Using interactive tools like the Portal series to draw them in makes physics, math, logic, spatial reasoning, probability, and problem-solving interesting, cool, and fun which gets us one step closer to our goal—engaged, thoughtful kids!" the company added.

Head here to grab your free copy of Portal.