Games released in 1991

Half-Life: Zombie Edition - a unique mod where you play as a zombie or headcrab in the Half-Life world, featuring a mutation system, three classes, and upgrades. This perspective from the enemy's side, the one you used to fight against, makes the gameplay unlike anything else.

Half-Life eXperiment - a story mod for Half-Life where you find yourself in an experimental research complex with unconventional map design: narrow corridors, labs with unusual architecture, and scenes built to maintain tension. Less large open spaces, more claustrophobia and survival.

Brutal Half-Life is a mod that turns the classic Half-Life into a fast-paced action game focused on brutality: dismemberment, lots of blood, new weapons, aiming, and kicking. Models and effects are improved, and maps inspired by iconic shooters have been added.

Half-Life 2: Classic is a fan-made demake of Half-Life 2 on the GoldSrc engine, showing how the game might have looked if Valve hadn't switched to Source.

E7 Black Star is a single-player Half-Life mod set in the secret laboratory complex Object E7 (Black Star) in Russia. The player takes the role of a political prisoner who tested a new HEV suit and escaped during the trials.

Half-Life: The Core — one of the most anticipated mods for Half-Life with impressive level detail that will give a new perspective on the disaster. It combines intense action, thoughtful puzzles and a story unfolding in completely new corners of the Black Mesa complex.

Hazardous-Course 2 is a parody mod for Half-Life that intentionally extends and complicates the original training course. Instead of the standard player training, the mod offers dangerous trials, puzzles, and platforming sections that require precision and attention.