The Aperture Science Handheld Portal Device appears in Portal when it is given to the protagonist of the game, Chell, as she takes part in a non-voluntary enrichment program. Chell receives the device near the start of the game, and for a while it only has the ability to place a single portal, as the other is created automatically depending on the level. Further on into the game however, Chell is presented with another device which allows her to place a second, and final portal.
The Portal Gun is the means to which the player completes the various courses set by GLaDOS. It creates two portals, an orange and a blue. As the player travels through one, their speed is conserved as they are instantaneously transported to the next portal. This provides advantages such as obtaining momentum to cross a gap, or creating a portal above an enemy, through which a weighted cube can be dropped. Another one of the Portal Gun's useful functions is the fact that it acts as a Gravity Gun, allowing certain objects to be picked up and carried easily, suspended in the air. Some limitations to the device are the fact that it cannot create portals on uneven surfaces, or any other material designed by Aperture Science to not allow portals. The gun is also disabled as it passes through what are known as in the games as "Aperture Science Material Emancipation Grills". Portals cannot be fired through these Emancipation Grills, and as the player travels through one, all currently open portals in the level are closed. These grills also vaporize anything that passes through besides the player or the portal device.
Because the portal gun is given to the participant (or maybe participants) as a means of testing how the human brain works, it is ironic then, that the device then becomes the sole reason that Chell manages to destroy GLaDOS and escape the Enrichment Center.
- The original model for the Portal Gun had the appearance of having been randomly put together from different pieces of tech. It also shot blue and purple portals. Later, it was changed to match the game's initial art style, white and smooth, yet high tech. It also now shot blue and orange portals.
- The Portal Gun used by Chell in the original game and in Portal 2, was white and black, and fired blue and orange portals. The Portal Gun used by ATLAS (player one) in Portal 2's co-op mode appears identical to Chell's, aside from a blue stripe identifying it as belonging to the blue robot. It, like the beta ASHPD mentioned above, fired blue and purple portals. P-Body's (player two) Portal Gun featured an orange stripe, and fired orange and red portals.