Half-Life 2: Episode One (stylized as HλLF-LIFE2: EPISODE ONE) is a first-person shooter video game, the first in an intended series of episodes that would serve as the sequels to Half-Life 2 (2004). It was developed by Valve Corporation and released on June 1, 2006. Initially called Half-Life 2: Aftermath, the game was renamed Episode One after Valve became confident in using an episodic structure for the game. Episode One uses the same game engine, Source, as Half-Life 2. The game debuted new lighting and animation technologies, as well as AI sidekick enhancements.
The game's events take place immediately after those in Half-Life 2, in and around war-torn City 17. Episode One follows scientist Gordon Freeman and his companion Alyx Vance in humanity's continuing struggle against the alien civilization known as the Combine. When the story begins, Gordon wakes up outside the enemy's base of operations, the Citadel, after being left unconscious from the concluding events of Half-Life 2. During the course of the game, Gordon travels with Alyx as they attempt to evacuate the city. As the game comes to an end, Gordon and Alyx are caught in a major accident, and their fates are revealed in the sequel, Episode Two.
Valve views episodes One through Three tantamount to a standalone release. Episode One is available as part of a bundle package known as The Orange Box, which also includes Half-Life 2, Episode Two, Team Fortress 2, and Portal. Episode One received a generally positive critical reaction, and the co-operative aspects of the gameplay received particular praise, although the game's short length was criticized.
Gameplay
In Episode One, players make their way through a linear series of levels and encounter various enemies and allies. The gameplay is broken up between combat-oriented challenges and physics-based puzzles. Episode One integrates tutorial-like tasks into the story to familiarize the player with new gameplay mechanics without breaking immersion. A head-up display appears on the screen to display the character's health, energy, and ammunition. Throughout the course of the game, the player accesses new weapons and ammunition that are used to defend the character from enemy forces. Unlike in Half-Life 2, where Gordon's first weapon is the crowbar, Gordon first acquires the Gravity Gun, which plays a crucial role in the game by allowing the player to use physics to manipulate objects at a distance in both combat and puzzle-solving scenarios.
The AI for Alyx Vance, Gordon's companion, was explicitly designed for co-operative play in Episode One to complement the player's abilities. The developers described Alyx's programming for Episode One as a "personality code" as opposed to an "AI code", emphasizing the attention they gave to make Alyx a unique and believable companion. For part of the code, she was explicitly programmed to avoid performing too many mechanical or repetitive actions, such as repeating lines of dialogue or performing certain routines in combat situations. Examples of this co-operative gameplay include combat in underground levels. In this scenario, the player can conserve their ammunition by using a flashlight to help Alyx spot and kill oncoming enemies. 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.
Synopsis
Setting
The original Half-Life takes place at a remote laboratory called the Black Mesa Research Facility. The player takes on the role of Gordon Freeman, a scientist involved in an accident that opens an inter-dimensional portal to the world of Xen and floods the facility with hostile alien creatures. After the player guides him in an attempt to escape the facility and close the portal, the game ends with a mysterious figure who offers Freeman employment. The protagonist is subsequently put into stasis by this mysterious character known as the G-Man.
Half-Life 2 picks up the story, in which the G-Man takes Freeman out of stasis and inserts him on a train en route to City 17 an indeterminate number of years after the events of the first game, with Earth now enslaved by the transhuman forces of the Combine. The player guides Gordon to aid in humanity's struggle against the Combine and its human representative, Dr. Wallace Breen. He oversees the occupation from his base of operations in the Citadel, a monolithic building at the heart of City 17. Fighting alongside Gordon is an underground resistance led by former colleague Dr. Eli Vance, as well other allies including Dr. Vance's daughter Alyx Vance and the enigmatic Vortigaunts, an alien species. Half-Life 2 ends with a climactic battle atop the Citadel that inflicts critical damage to its dark fusion reactor. When it seems as if Alyx and Gordon are to be engulfed by the explosion, the G-Man appears once more. After giving a cryptic speech, he extracts Gordon from danger and places him in stasis once again.
Plot
After the explosion of the Citadel reactor from which Gordon was extracted by the G-Man and where Alyx Vance was left behind, time suddenly freezes. Several Vortigaunts appear and rescue Alyx from the blast. After she is rescued, the Vortigaunts appear before the G-Man and stand between him and Gordon. They teleport Gordon away from the scene, much to the G-Man's displeasure.
D0g retrieves Gordon out from under some rubble outside the Citadel, and Gordon reunites with Alyx, who is relieved to see him. Alyx contacts Eli Vance and Isaac Kleiner, who have escaped the city, and is informed the Citadel's core is at risk of exploding at any moment. Kleiner states the explosion could be large enough to level the whole of City 17, and the only way for them to survive is to re-enter the Citadel and slow the core's progression toward meltdown. Eli reluctantly agrees when he sees no other option.
Alyx and Gordon re-enter the now-decaying Citadel to try to stabilize the core; Gordon is successful in re-engaging the reactor's containment field, which delays the explosion. Alyx discovers the Combine are deliberately accelerating the destruction of the Citadel to send a "transmission packet" to the Combine's homeworld. She downloads a copy of the message, which causes the Combine to prioritize them as targets. Alyx also downloads a transmission from Dr. Judith Mossman, in which she mentions a "project" she has located, before she is cut off by a Combine attack. Afterward, Alyx and Gordon board a train to escape the Citadel.
The train derails en route, forcing the duo to proceed on foot. As they fight through the disorganized Combine forces and rampant alien infestations, Kleiner appears on the screens Breen once used to pass out propaganda, and gives out useful updates to the evacuating citizens about the latest turn of events as well as reiterating the Citadel's imminent collapse. Alyx and Gordon eventually meet up with Barney Calhoun and a group of other survivors who are preparing to move on a train station to escape City 17. Alyx and Gordon provide cover for the passengers as they board.
