Valve Software has made its popular physics puzzler Portal free until September 20, hoping to see it used in classrooms.
"When we heard the buzz surrounding the new role video games are playing in education, we had to throw our hat in the ring," said the developer.
"Innovative educators are finding ways to incorporate Portal and Portal 2 into their classrooms-helping teach physics and critical-thinking skills. It's eye-opening to see how video games can be used in amazing and unexpected ways to help educate our next generation."
A free copy of the game can be obtained at the Learn With Portals site.