Opposing Force is without a doubt one of the strangest and most unique entries into the Half-Life canon in how different its goals as a game are. Unlike the Valve-produced HL games, Opposing Force isn't trying to be revolutionary or showcase any new crazy technology or push the medium of FPS to uncharted territory. Instead, it's focused on the expected: being a standard expansion pack providing us with more Half-Life. That actually makes Opposing Force and its expansion-pack brethren truly anomalous within the Half-Life canon, and you can see that present in everything from its game and level design to its atmosphere and aesthetic. The levels feel a bit too empty and compressed, attempting to mimic the immersive magic of the original game's portrayal of Black Mesa but being limited by its scope as an expansion pack. The story and its premise are brand-new and intriguing, but is executed with the exact same plot beats of the original.
What you get according to most people is a very derivative Half-Life game. But for me, its attempts to mimic Half-Life's magic quickly endeared me in it sort of gave a very uncanny valley vibe for me. It all feels a bit off and alien, which weirdly enough kinda fits the game's premise of giving us a new perspective of the Black Mesa incident. The weird new enemies that are exclusive to this game and not mentioned at all in base Half-Life give that similar underdog, scrappy vibe that extended-universe media tends to have when trying to add to the canon without being reciprocated by the original developers. For a lot of people that's a con, and understandably so! Maybe it's just from me experiencing and re-experiencing all the mainline Half-Life games and playing the expansion packs last, but the experimental (but not too groundbreaking) gameplay really struck a balance with me-- feeling new and fresh, but still undeniably Half-Life.
And that brings me to where this game shines despite being derivative in a lot of ways. The new stuff it does is just awesome. The brand-new weapons pack so much punch and have this deliciously impactful feel to them: the machine gun, wrench, weird green thingy that shoots spores. This is no doubt largely contributed to by the new Race X aliens, who are INSANELY tanky. I'm seeing others complaining about that fact and it did lead to a lot of frustrating deaths, admittedly, but defeating them remained a dopamine-inducing moment each and every time because of their tankiness.
You also get incentivized a lot more to actually ask NPCs to follow you, primarily because the majority of the NPCs you run into in Opposing Force are fellow Marines who are actually equipped with weaponry to handle the tougher enemies and all have awesome unique roles that honestly make you mourn them a bit when you lose them, contrasted to how comical/apathetic deaths in the original Half-Life could get.
Of course, not everything hits and there's an undeniable level of jank and lack of polish compared to the original Half-Life. You've still got buggy NPC pathfinding, frustrating save points, a few parts where it's insanely easy to get lost or not know what to do next, etc., etc. However, after finally playing Opposing Force for myself, I found it to strangely be a worthwhile and unique entry worth playing in the Half-Life canon despite it on the surface just offering "more Half-Life". In those attempts to be more Half-Life, I've found it kind of ends up being completely unique to the rest of the series, and in a really good way, too.
