The Cake Is A Lie - Gameplay

Gameplay

A more advanced portal technique. The character builds up speed using two blue portals, to reach an otherwise unreachable area. The second blue portal is carefully created mid-air, after exiting the orange portal for the first time, destroying the first blue portal in the process.

In Portal, the player controls the protagonist, Chell, from a first-person perspective as she is challenged to navigate through a series of rooms using the Aperture Science Handheld Portal Device, or portal gun. The portal gun can create two distinct portal ends, orange and blue. The portals create a visual and physical connection between two different locations in three-dimensional space. Neither end is specifically an entrance or exit; all objects that travel through one portal will exit through the other. An important aspect of the game's physics is momentum redirection. As moving objects pass through portals, they come through the exit portal at the same direction as the exit portal is facing and with the same speed with which they passed through the entrance portal. For example, a common maneuver is to jump down to a portal on the floor and emerge through a wall, flying over a gap or another obstacle. This allows the player to launch objects or Chell herself over great distances, both vertically and horizontally, referred to as 'flinging' by Valve. As GLaDOS puts it, "In layman's terms: speedy thing goes in, speedy thing comes out". If portal ends are not on parallel planes, the character passing through is reoriented to be upright with respect to gravity after leaving a portal end.

Chell and all other objects in the game that can fit into the portal ends will pass through the portal. However, a portal shot cannot pass through an open portal; it will simply deactivate or create a new portal in an offset position. Creating a portal end instantly deactivates an existing portal end of the same color. Moving objects, glass, special wall surfaces, liquids, or areas that are too small will not be able to anchor portals. Chell is sometimes provided with cubes that she can pick up and use to climb on or to hold down large buttons that open doors or activate mechanisms. Particle fields known as emancipation grills, occasionally called "fizzlers" in the developer commentary, exist at the end of all and within some test chambers; when passed through, they will deactivate any portals that are still operating and disintegrate any object carried through. The fields also block attempts to fire portals through them.

Although Chell is equipped with mechanized heel springs to prevent damage from falling, she can be killed by various other hazards in the test chambers, such as turret guns, bouncing balls of energy, and toxic liquid. She can also be killed by objects falling through portals, and by a series of crushers that appear in certain levels. Unlike most action games at the time, there is no health indicator; Chell dies if she is dealt a certain amount of damage in a short time period, but returns to full health fairly quickly. Some obstacles, such as the energy balls and crushing pistons, deal fatal damage with a single blow.

GameSpot noted, in its initial review of Portal, that many solutions exist for completing each puzzle, and that the gameplay "gets even crazier, and the diagrams shown in the trailer showed some incredibly crazy things that you can attempt." Two additional modes are unlocked upon the completion of the game that challenge the player to work out alternative methods of solving each test chamber. Challenge maps are unlocked near the halfway point and Advanced Chambers are unlocked when the game is completed. In Challenge mode, levels are revisited with the added goal of completing the test chamber either with as little time, with the least number of portals, or with the fewest footsteps possible. In Advanced mode, certain levels are made more complex with the addition of more obstacles and hazards.

The PC, Xbox 360 and Mac OS X versions of the game also feature a number of achievements the player can earn by completing tasks. Achievements range from normal gameplay requirements, such as obtaining the Aperture Science Handheld Portal Device, to various tricks, such as using portals to jump a particular distance. As with other Source engine games since Half-Life 2, Portal can be played with commentary enabled; special icons will appear in the game that the player can activate to hear how certain parts of the game were developed.