The PlayStation 2 version of Half-Life is a port of the Windows game, but with significant changes to the weapons, character models, map geometry, and some extended levels. The game also includes an expansion pack referred to as Half-Life: Decay .
The story takes place at the same time as the original Half-Life , but from the perspective of other characters. The add-on consists of fixed, separate missions with a more puzzle-oriented approach and cooperative gameplay for two players in split-screen mode. Players can also complete singleplayer mode, switching between characters to advance.
The game features unique missions with statistics shown at the end of each one, where players are graded and can unlock a bonus mission by achieving an A grade. Completing this bonus mission allows players to control and work together as two Vortigaunts in any singleplayer mode. The game supports USB mouse and keyboard for more precise control.