Half-Life: Opposing Force

Half-Life: Opposing Force retells the Black Mesa catastrophe from the other end of the barrel. The player takes on soldier Adrian Shephard, a member of the squad that flew into the original game to clean up the complex and eliminate witnesses. The landing goes wrong, the unit is scattered, and Shephard fights his way through the wrecked facility, running into surviving colleagues, terrified scientists, and alien creatures from Xen. The expansion sticks to the structure of the original, uninterrupted storytelling with no cutscenes, but frames the scenes from a different angle: places that were the site of the action in Half-Life are now shown as the aftermath.

Gearbox added more to the gameplay than an expansion pack was expected to deliver. The new arsenal spans military weapons and organic Xen items where living creatures are used instead of ammunition, and allied soldiers join your party with the abilities the player needs at that moment: a medic heals, an engineer opens locked doors, a heavy trooper covers you with suppressing fire. There are also climbing sections, object-carrying puzzles, and machine operation, so the pacing regularly alternates between firefights and quieter stretches. Technically it all runs on the GoldSrc engine with improved models and effects, running smoothly even on period computers, with hardware acceleration support and a typically restrained but tense soundscape full of vent hums and distant gunfire.

At the time the expansion was hailed as one of the best add-ons ever released for a shooter, precisely because it offered a new perspective on a familiar story instead of just a map pack. It also brought its own multiplayer and further support for the community that was thriving around Half-Life at the time. Today Opposing Force feels like a compact, well-paced campaign for an evening or two, and it's the ideal follow-up right after finishing the original game. Its age shows in the simple graphics and occasionally confusing navigation, but the way it tells its story without wresting control from the player is still exemplary.