[4] Alyx appears in the video game Half-Life 2 as a recurring ally to protagonist Gordon Freeman, and the daughter of Eli Vance, all of whom operate as members of the Resistance.

In Half-Life 2: Episode Two, Alyx and Gordon travel to the White Forest Rocket Facility to deliver a crucial information packet stolen from the Citadel.

She delivers the Combine data to Dr. Kleiner, who manages to decrypt it and discover that Judith Mossman has found the legendary Borealis, an icebreaker ship which has disappeared during teleportation experiments.

She delivers the message to her father after the G-Man triggers her programming, and later, two creatures called Advisors break in and kill Eli before Dog saves Gordon and Alyx.

He gives her the power to kill the Advisor, saving Eli's life, but puts her in stasis to replace Gordon Freeman, causing her to be removed from time.

[6] In Episode One, where Alyx's role as a companion is expanded upon, her artificial intelligence (AI) was designed specifically for co-operative play to complement the player's abilities.

[7] Examples of this co-operative gameplay include combat in underground levels, where the player can use their flashlight to help Alyx spot and kill oncoming enemies, thereby conserving their own ammunition.

[8] Similarly, Alyx will often take up strategic positions and provide covering fire to keep the player safe while they travel to a certain area or perform certain actions.

[12] Entertainment Weekly's Darren Franich considered her one of the best female characters, feeling that she was a vital component to the game due to Gordon being a silent protagonist.