Portal is designed to change the way players approach, manipulate, and surmise the possibilities in a given environment; similar to how Half-Life 2’s Gravity Gun innovated new ways to leverage an object in any given situation.

Players must solve physical puzzles and challenges by opening portals to maneuvering objects, and themselves, through space.

To get in on the fun you just need to install the Steam client for PC or Mac, then hit the Steam store and “purchase” Portal for the grand total of $0.00. Don’t delay though, as this offer is only good until Sept. 20, 2011.