"Subject name here" and "subject hometown here" were delivered in a different, somewhat less distinct, tone of voice, highlighting the lack of personal information as if to make the existing lack of humanity in Portal's cold, sterile environments that much less personal.

Of course, it's also funny. Portal's writing is the work of Erik Wolpaw and Chet Faliszek, best known as the writers of the celebrated--but sadly now largely defunct--gaming website Old Man Murray; Wolpaw also has experience with video game comedy writing as designer Tim Schafer's co-writer on Double Fine's Psychonauts. Wolpaw and Faliszek are now on Valve's full time writing team along with longtime Half-Life scribe Marc Laidlaw.

Despite the pedigree of its writers, Portal remains an intensely, and refreshingly, gameplay-oriented game. It centers around the manipulation of a portal-shooting gun that creates entry points and exit points on flat surfaces, allowing its user to teleport or transport objects instantaneously from one point to another. This basic mechanic forms the fundamental building block of the game's series of puzzles, which become more and more creative and complex as they progress.

Portals can be used to incapacitate hostile gun turrets by casting a portal above the turret and dropping a crate through another, knocking over the turret and rendering it useless. With a bit of timing, they can be used to drop down onto moving platforms. They can be used to transport crates where they are needed, or to drop them onto large buttons that need pushing. They can be used to re-route the floating energy balls previously seen in Half-Life 2, guiding them to recepticles that, when filled, lead to results elsewhere. They can allow you to bypass a room full of obstacles--until it becomes clear that, in order to achieve a particular goal, you must plant opposing portals in separate accessible only via opposite sides of the obstacle room.

Perhaps most ingeniously, and very satisfyingly, portals do not break the momentum of objects traveling through them, but they do reorient the direction of momentum according to the angle of the surface on which they are placed. This means that one can plant a portal on an upwardly inclined surface and another on the floor below a long drop, then jump down into the first portal and end up launched through the second at an angle, with all the momentum gained from the initial fall. After completing a few challenges based on this principle, one begins to imagine some complex but enticing possibilities involving launching through portals and casting new target portals in mid-air based on one's current trajectory.

Portal is the spiritual successor to Narbacular Drop, a free game created by students at the DigiPen Institute of Technology built around the portal-based puzzle concept. Impressed, Valve hired several of its team members to create Portal, which takes Narbacular Drop's concept, refines and expands it, and adds the Valve sheen. Valve's Kim Swift and Jeep Barnett, who served as programmers on Narbacular Drop, admitted that after having spent so much time developing Portal, it can be a little tough to go back and play Narbacular Drop again (but don't let that stop you; it's a blast!). Laughing, fellow Valve employee Doug Lombardi chimed in, "At Valve, what you work on should always make your previous work look like shit."

Set within the Half-Life universe, Portal breaks from the franchise's previously constant focus on the exploits of Gordon Freeman in the aftermath of the Black Mesa incident--or, at least, it seems to. I asked team members if Portal eventually ties into the larger events of the Half-Life universe, and while the carefully noncommittal answers I received strongly suggested that it does, it remains to be seen how and to what extent. "We would prefer to let players come to those discoveries themselves," explained Valve's David Speyrer.

Another element of Portal that runs counter to the conventions of the Half-Life series is that it is quite easy to see the player character, who is, in another series first, a woman. By simply positioning oneself in between two facing portals, one may look through either portal and see oneself on the other side. This novel mechanic works several levels deep, like looking into facing mirrors, and when employed slightly more creatively can be used to see the player character from a variety of angles.

There is little focus on health or other player statistics; there is in fact no HUD at all. Health is very much downplayed, and regenerates over time as in Infinity Ward's Call of Duty or Bungie's Halo 2. Still, there are frequently situations that are genuinely dangerous. "Any contact with the chamber floor will result in an unsatisfactory score," relays the monotone narrator in one room, "followed by death."

With an impressively strong set of central gameplay mechanics and a surprisingly engaging sense of atmosphere and humor, Portal is shaping up to be one of the most unique titles of the year by any measure. Titles so fundamentally and elegantly structured around such a novel gameplay concept are practically unheard of in the realm of current, full-3D, polished games from large, established developers, and Portal is a reminder of what is wrong with that picture.

Valve plans to ship Portal this fall, initially sold as part of Half-Life 2: The Black Box and Half-Life 2: The Orange Box for PC, and Half-Life 2: The Orange Box for PlayStation 3 and Xbox 360.