Portal

Portal is an action first person shooter game developed by the creators of Narbacular Drop after they were hired by Valve Software and published by Valve on Steam. It was also included as part of The Orange Box.

Plot
The plot of Portal revolves around Chell, the main character, completing increasingly difficult tests for Aperture Science (a competitor to Black Mesa for Federal funding) while being directed by GLaDOS (Genetic Lifeform and Disk Operating System, voiced by Ellen McLain), a super computer. Chell runs through increasingly difficult obstacle courses using the Aperture Science Handheld Portal Device. When she first gets it, it can only fire blue portals, but it is later upgraded to fire orange portals as well. Either portal can be entered, causing Chell to emerge from the other portal, wherever it may be. Both portals must be active to enable transit between them.

Eventually, GLaDOS will betray you in the final test. Chell escapes the death trap, running through a disused laboratory before encountering and destroying GLaDOS. This causes a huge explosion ending the game and (possibly) the lab.

Gameplay
Portal starts with Chell in a room or dormitory with instructions being given via a radio located on the table nearby. At this point in the game she has no access to her weapon, the portal gun, but she can pick up, move, throw, push, and drop objects. Soon she is released from the room and begins her Aperture Science testing.

Gameplay consists of levels that of increasing difficulty where the main goal is to reach the elevator to proceed to the next level. These levels range from lifting blocks to hold down buttons, all the way to navigating a cylinder of moving tubes to try and reach the top.

As she progresses through the levels, she finds a portal gun, and later, an upgrade for it which allows her to create both halves of the portals that allow her to proceed from one obstacle to the next.

Objects
Several obstacles can be found in the Aperture Science Computer-Aided Enrichment Centre. Some of these obstacles include: portal you--| |      ______________ destination __________________|___   |           _______________________                                |    |         |                             |    |         |                              |other portal  | |______________|
 * The Materials Emancipation Grill - "Portal Stoppers", also known as fizzlers, are blue transparent walls that you may pass through however portals may not be fired through it. Also, items (such as the Weighted Storage Cube) may not be carried through.
 * Portal-proof walls - Solid walls that neither you or the portals may pass through. These are typically made of metal.
 * Floor switches - Large red buttons that your weight, the "companion cube" or a regular cube's weight may press in order to activate doors or other devices in the level.
 * Large gaps - Spaces in the floor which you will need to traverse by momentum.


 * Toxic Water/Waste - Liquid placed on floors of level that must be avoided, contact results in immediate death.
 * Robot turrets - Small robots with laser sights; if found in sights the turret will shoot.
 * Robot rocket launchers - Found in later levels, large stationary robots that shoot rockets very slowly, always used to get closer to winning the game.
 * Energy balls - These balls (which resemble the Combine Energy Balls seen in Half-Life 2) must be directed into receptors to power lifts or other devices. Contact with an energy ball results in vaporization.
 * Incinerator - The final resting place of the Weighted Companion Cube.

Relation to the Half-Life Universe
There are a number of references to the Black Mesa corporation (owner of the Black Mesa Research Institute, where most of the first Half-Life game takes place) in the disused part of the Enrichment Centre. Also, in Half-Life 2: Episode Two it is mentioned that the Borealis, a ship owned by Aperture Science, disappeared with most of its cargo while in dry dock.

Finally, near the end of the game, GLaDOS states that something was coming that not even she could stop. This could be the Portal Storms caused by the resonance cascade in Half-Life or it could mean the rise of the Combine.