Half-Life 2: Episode One - Gameplay

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 heads-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 initial 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 designed specifically 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 specifically 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.