Portal is free on Steam until September 20

It's easy to miss the complex problem solving and spatial reasoning needed to complete Portal because the game is so engaging. But even though Portal will be four years old next month, its physics-based puzzles still require critical thinking way beyond today's average first-person shooter. That's probably why some classrooms, like The Evergreen School's seventh grade, have chosen to use Portal as a learning tool.

Valve recently invited the seventh graders to take a field trip to its studios where teams of three learned how to use the Hammer level editor and create their own rooms in the game. For educators the trip was a great way to bridge the gap between the math and physics being taught in the classroom with examples of real-world professionals using those skills to create amazing things. For Valve it was exciting to see their software being used in such a positive way. In fact, the company was so happy with the trip that they documented the trip with a short video and made Portal available for free until September 20.

The free version isn't just for students and it's not a trial version of the game due to expire in a few days. Anyone can download the full game for Mac or PC from Steam right now. Be cautious though because this game may be educational. And if we learned anything from Math Blasters and Mavis Beacon Teaches Typing, it's that learning is boring — at least it used to be.