I was knee-deep working as a technical game designer + engine programmer on Soldier of Fortune when Half-Life came out. I can't put into words the impression that the opening that game left on me; I still remember very distinctly experiencing the tram ride, just being utterly entranced, and then being deeply irritated when an artist walked over to my cubicle, saw the game, and jokily asked what was going on, pulling me out of the experience. For me, it was one of those singular experiences you only have a very, very rarely in gaming.<p>It's funny, though - I would say in retrospect that Half-Life had the typical vexed impact of a truly revolutionary game made by a truly revolutionary team. In terms of design, the Half-Life team was asking and exploring a hundred different interesting questions about first person gaming and design, very close to the transition from 2d to 3d. And their influence, a few years later, often reduced down to a small handful of big ideas for later games influenced by them. After Half-Life, because of the impact of their scripted sequences, FPS games shifted to much more linear level designs to support that kind of roller coaster experience (despite many of Half-Life's levels actually harkening back to older, less linear FPS design). The role of Barneys and other AI character also really marked the shift to AI buddies being a focus in shooters. And the aesthetic experience of the aggressive AI from the marines as enemies also cast a long shadow, too, highlighting the idea of enemy AI being a priority in single player FPS games.<p>Certainly, those were the biggest features of Half-Life that impacted our design in Soldier of Fortune, which did go on to shift to much more linear levels, much more focus on scripted events, and would have resulted in much more emphasis on AI buddies too if I hadn't really put my foot down as a game programmer (and in my defense, if you go back to FPS games from that era, poorly implemented AI buddies are often, by a wide margin, the most frustrating aspect of that era of games, along with forced poorly done stealth missions or poorly implemented drivable vehicles - the fact that Barneys were non-essential is why they worked well in the original Half-Life). You can see this shadow pretty clearly if you compare Half-Life to, afterwards, the single player aspects of Call of Duty and Halo. Both are series that, in their single player form, are a lot more focused and a lot less varied than Half-Life was, but they clearly emphasize those aspects of Half-Life I just mentioned. And in practice, those were the single player FPS games that were in practice actually copied for quite a while.