Valve has made its critically acclaimed first-person puzzler Portal available for free.
The original game, which first debuted in 2007 Half-Life compilation The Orange Box, can be downloaded at no cost on both PC and Mac. However, Rock Paper Shotgun reports this offer is only available until September 20th.
This price promotion is part of Valve's games and learning initiative called Learn With Portals. The program involves educators teaching physics using Portal and Portal 2
"It's eye-opening to see how video games can be used in amazing and unexpected ways to help educate our next generation,” Valve said in a statement.
Using interactive tools like the Portal series to draw them in makes physics, maths, logic, spatial reasoning, probability, and problem-solving interesting, cool, and fun which gets us one step closer to our goal—engaged, thoughtful kids.”