Portal (video game)

Portal is a puzzle video game made by Valve Corporation set inside the "Half-Life" series. It was originally sold in "The Orange Box", a game collection deal which came with the Valve-made games "Portal", "Half-Life 2", and "Team Fortress 2". It is now sold by itself and is available for Xbox 360, PlayStation 3, Mac and PC.
The player plays as a woman named Chell who has to go though tests while being watched by a computer named GLaDOS, an acronym for Genetic Lifeform and Disk Operating System. GLaDOS provides all of the game's dialog and is known for being clever, funny, and sarcastic, promising the player character a cake if all of the tests are finished. GLaDOS and the testing rooms were created by a company called Aperture Science, which competes with Black Mesa. The player must use a gun, called the Portal Gun, that makes two linked holes, called portals, to solve puzzles. The two portals, one blue and one orange, are linked together and let the player get from one place to another. When the player enters the blue portal, they will come out of the orange portal. When the player enters the orange portal, they will come out of the blue portal.
Portal has many jokes in it that have become popular on the internet, for example, "the cake is a lie". Because the game was very popular, Valve made a sequel in 2011, called "Portal 2".
Plot.
The game starts with Chell waking up in a small glass room that has only a bed, a toilet, and a radio inside. She is told by GLaDOS that testing will start soon, and an orange portal opens on one of the walls. Once the player goes through, she enters the testing rooms and begins testing. There are 20 testing rooms, called Test Chambers, in all.
The tests start out simple. Chell has to pick up boxes, called Weighted Storage Cubes (Cubes for short), and put them on buttons, which will open the door to the exit of the chamber. At this point, GLaDOS speaks to Chell as a guide, praises her, and promises her cake when the tests are over. Near the beginning of the game, Chell gets the Aperture Science Handheld Portal Device, also known as the Portal Gun. At first, her Portal Gun only makes blue portals and the orange portals are made by GLaDOS. Later, Chell gets the full Portal Gun and can make both blue and orange portals.
The tests become more and more dangerous farther into the game. In some rooms, there is poison on the floor. In others, there are balls of electricity called High Energy Pellets which will kill Chell if she touches them. During these tests, GLaDOS becomes more and more sarcastic, giving Chell useless advice, such as "The floor here will kill you. Try to avoid it." At one point, GLaDOS tells Chell a chamber is broken and she must go through a chamber full of sentry guns, called Turrets, instead. If a Turret sees Chell, it will shoot at her until she dies. In this chamber is a hidden room. In the hidden room are drawings and writing on the walls left by an unknown person. The writing says things like "the cake is a lie" and "she's always watching" with a picture of a camera. There are more rooms like this in later chambers.
In another chamber, Chell has to use the Weighted Companion Cube, which looks like a Weighted Storage Cube with hearts on it, to solve the test. During the test, GLaDOS tells Chell several times that the Companion Cube is not alive, but at the end of the test, she tells Chell she has to "kill" the Companion Cube to get to the next test. 
During the last test, Chell has to stand on a moving platform. At the end of the platform's track, it will carry her into a fire pit. GLaDOS thanks Chell for doing the tests. At the last minute, Chell uses her Portal Gun to escape the trap. While trying to escape the building, Chell is led into a room where she finds GLaDOS. Chell breaks a white ball that fell out of GLaDOS. GLaDOS tells her she was stupid to break it because they did not know what it was, but GLaDOS quickly figures out it was her morality core. She tells Chell the people who worked for Aperture Science installed it to make her stop killing them with "Deadly Neuro-Toxin". Because Chell broke it, GLaDOS can use the Neuro-Toxin again. Chell has a time limit of 6 minutes to kill GLaDOS before the Neuro-Toxin kills Chell. After breaking pieces off of her and burning them, GLaDOS is destroyed and Chell escapes the building. 
After Chell escapes, she faints, and a robot drags her back into the building. During the credits, GLaDOS sings a song called "Still Alive" written by Jonathan Coulton, that says even though Chell killed her, she is still alive.
Gameplay.
"Portal" is a first-person shooter game, which means that it is played from the view of the player character, Chell. When players get the fully-powered portal gun, they can make two portals that are linked together on some white surfaces. Chell starts out with nothing, only able to do what GLaDOS lets her, such as entering portals created by GLaDOS and using cubes that GLaDOS gives her. Once Chell gets a half-powered portal gun, she can fire a blue portal that connects to orange portals that GLaDOS puts in the rooms. When Chell gets the fully-powered portal gun, she can put both portals anywhere. 
The portals are linked, making a tunnel that Chell can walk through. The tunnel works in both directions, so if Chell enters a blue portal, she will exit from an orange portal, and if she enters an orange portal, she will exit from a blue portal. The purpose of the portals is to make shortcuts to different areas, for example, if the player needs to get to a high ledge but is unable to jump to it, they can put a blue portal at their level and fire an orange portal above the ledge. Going through those portals will get the player onto the ledge.
The portals can be used in different ways, notably as a way to catapult Chell. If the player cannot put a portal on a high ledge but can put one on a wall across from the ledge and one on the floor below, these portals can be used to propel Chell forward far enough to reach the ledge. This is because portals do not affect forward momentum. When Chell enters the portal in the floor and exits the portal in the wall, she will fall, gaining speed. If she goes through the portal on the floor again while falling, she will be going fast enough that when she exits the wall portal again, she will be able to land on the ledge.
The different ways the portals work together mean there are multiple ways to solve the puzzles in the Test Chambers.