Portal is a puzzle/platforming game that follows an unnamed test subject as they are put through an automated testing system. The subject's mental and physical prowess is challenged as the testing rooms become more and more deadly. With only a portal gun and their own wits to sustain them, the subject must complete the rigors before them or die.
There are levels where toxic water is underneath the Player Character. If the Player Character falls in they die, possibly from being harmed from the water. Also touching the water harms the Player Character.
After the main testing areas are finished, the platforming areas become shadowed and dark. They are never so dark that the player cannot see the environment around them and nothing will jump out at the player.
The Player Character is reduced to nothing but a test subject in the game. The Player Character is never named and only referred to by their testing number. After finishing testing the computer administrating the tests states that the Player Character should be disposed of because they are no longer of use.
It is implied in the game that there are other test subjects also being dehumanized in the game. No other subjects are met in game.
The computer administering the tests is intentionally verbally abusive towards the Player Character. The statements are occasionally threatening or insulting. The verbal abuse is ongoing and includes the computer condescending to or mocking the player repeatedly. This abuse is present throughout the game.
The game implies in the beginning Player Character's sole purpose is to be a test subject, i.e. that they have no other meaning or worth in the world.
Ratman (unnamed in game) is a scientist who participated in the lab prior to the events in the game. After the computer took over, he made several lairs throughout the game that the player can choose to explore. These lairs contain assorted phrases (the cake is a lie, help, etc.) and tally marks that show his eventual despair and descent into madness. These places are not required to be explored and can be avoided by not exploring the areas after the main testing part of the game.
The plasma/electricity balls disintegrate with a faint smashing sound, although it is not violent-sounding.
The boss battle involves explosions via guided rockets being aimed at the player. These are used to damage a sentient computer. The explosion lasts for a split second and is always warned against by a series of distinctive beeps.
Turrets are present in some levels and shoot bullets at the Player Character. They make gun noises and there are bullet trajectories shown on screen. If the Player Character is hit blood spatters appear.
The main game mechanic revolves around a portal gun that is shaped somewhat like a gun and fires portals. It is not used in-game as a weapon.
This game involves a lot of heights, and using heights to progress to checkpoints. The Player Character uses momentum to jump, and the player has a first person experience of falling. The Player Character is equipped with boots that allow her to land without injury from an indefinite freefall, so there is no risk of gore or death from falling.
It is implied that the Player Character was a voluntary test subject for a legitimate laboratory. However, the plot reveals that the computer took over and began testing subjects in violation of ethical medical procedures.
Ratman (unnamed in game) is a scientist who participated in the lab prior to the events in the game. After the computer took over, he made several lairs throughout the game that the player can choose to explore. These lairs contain assorted phrases (the cake is a lie, help, etc.) and tally marks that show his eventual descent into madness; his mental issues are implied to be exacerbated by the trauma of the computer antagonist trying to kill him. These places are not required to be explored and can be avoided by not exploring the areas after the main testing part of the game.
The Player Character is forced to throw away the companion cube, which they supposedly had a fondness for. Though it is not shown in-game, the antagonist states that often subjects form attachments to the cube and are traumatized by its destruction.
Though it is implied that the Player Character may have originally been a volunteer, they are not given the option to leave the testing areas. They are forced against their will to complete the tests or die.