Portal

"Now you're thinking with portals."

- GLaDOS during the Portal trailer

Portal is a single-player first-person puzzle game developed by Valve. The game was released in a bundle package known as The Orange Box for PC and Xbox 360 on October 9, 2007, and for the PlayStation 3 on December 11, 2007. The Microsoft Windows and Mac OS X versions of the game are also available for download separately through Valve's online delivery platform Steam and was released as a standalone retail product on April 9, 2008. The game consists of a series of puzzles which must be solved by teleporting the player's character and other simple objects using the Aperture Science Handheld Portal Device. The goal of each chamber is to reach an exit point, represented by a circular elevator. The "portal gun" and the unusual physics it creates are the emphasis of this game.

Plot
Portal follows the journey of Chell, a test subject awakened from stasis by GLaDOS, a sentient, murderous AI.

Characters

 * Chell
 * GLaDOS
 * Party Escort Bot
 * Doug Rattmann

Enemies

 * GLaDOS
 * Aperture Science Sentry Turret
 * Rocket Sentry

Gameplay


In Portal, the player controls Chell (as she is named in the game credits), a test subject in the Enrichment Center. Gameplay revolves around the Aperture Science Handheld Portal Device (also known as the "Portal Gun", or ASHPD, the acronym), a handheld device that can create an inter-spatial portal between flat planes, allowing instant travel and a visual and physical connection between any two different locations in 3D space. Portal ends are restricted to planar surfaces, but if the portal ends are on different planes, bizarre twists in geometry and gravity can occur, such as the player walking into the portal through a wall and "falling" up out of the floor several feet behind where she started. An important aspect is that objects retain their momentum as they pass through the portals: an object that falls some distance before entering a portal will continue moving at that same speed out of the other end. This allows the player to launch objects, including Chell, up to higher levels that lack appropriate portal surfaces. Only two portal ends may be open at a time, one orange and one blue in color. If a new portal end is created, it replaces the previous portal of the same color. Either color may be used as an entrance or exit portal. The portal gun is also used to pick up objects in a similar manner to the Zero Point Energy Field Manipulator (Half-Life 2), although it cannot propel objects or pull them from afar like the Gravity Gun can.

Guided by a supercomputer named GLaDOS (an acronym for Genetic Lifeform and Disk Operating System, voiced by Ellen McLain), players use the portal gun to perform a variety of tests, such as creating portals to knock over turrets and moving to a previously unreachable area.

In their initial preview of Portal, GameSpot gave an example of a gameplay scenario: In other situations, the player may be under fire by a gun sentry. So all the player needs to do is shoot a portal open over the gun, then shoot a portal open beneath a crate, then watch the crate fall through the hole and crush the gun. It gets even crazier, and the diagrams shown in the trailer showed some incredibly crazy things that the player can attempt, like creating a series of Portals so that the player is constantly chasing herself.

Two additional modes are unlocked upon completion of the main game. In Challenge mode, the player has to get through a test in either as little time, with the least number of portals, or as few footsteps as possible. In Advanced mode, the hardest levels of the game are made even harder with the addition of more obstacles and hazards.

Development
Portal is Valve's professionally-developed spiritual successor to the freeware Narbacular Drop, the 2005 independent game released by students of the DigiPen; the original Drop team are now all employed at Valve. Certain elements, like the orange/blue system of identifying the two different portal ends a player can have open at a time (one connecting to the other), have been retained. The key difference in the signature portal mechanic between the two games is that in Narbacular Drop the player can place a portal on a wall visible through another portal, whereas in Portal, the HPD cannot fire a portal shot through a portal; however, the HPD can fire a portal shot while the player is standing in a portal.

Sequel and spin-offs
On March 5, 2010, Portal 2 was officially announced, after a series of cryptic clues were released in the form of an update to Portal. It was released on April 19, 2011.

Portal: Still Alive
Portal: Still Alive is an exclusive Xbox Live Arcade game released in October 2008, and features new levels and achievements. The additional content is drawn from levels from the map based on "Portal: The Flash Version" by We Create Stuff and contains no additional story-related levels. According to Valve spokesman Doug Lombardi, Valve had been in discussion with Microsoft to bring Portal to the Xbox Live Marketplace, but was limited by the amount bandwidth that Microsoft was willing to allow for such content.

Critical reception
Portal has had an extremely good reception from critics. As of December 31, 2007 on the review aggregator Game Rankings, the Windows version of the game had an average score of 90% based on 19 reviews. On Metacritic (as of February 2, 2009), the Windows version had an average score of 90 out of 100, based on 28 reviews, while users gave it a 9.6 out of 10 based on 1644 reviews.

Trivia

 * The type of cake promised to the player is a Black Forest cake.


 * The Portal team worked with Half-Life series writer Marc Laidlaw on fitting the game into the series' plot. Erik Wolpaw and Chet Faliszek of the classic gaming commentary/comedy website Old Man Murray had been hired by Valve and put to work on the dialogue for Portal.


 * Portal, like other recent Valve releases, includes a commentary feature.


 * You can spawn the same nPCs, with the 'npc_create' console command, in Portal as in Half-Life 2: Episode One, because it uses Episode One as the basis for models. Note that no Episode One NPCs have sounds except the Citizen, who has a death sound.