When a highly influential game like Half-Life (1998) comes around, its always worth remembering that as influential as they may be, they rarely come from nowhere. Through the mid 90s a variety of games were experimenting with how to tell stories in the format of an FPS. Star Wars: Dark Forces (1995) created a surprisingly modern feel with its approach. Where Doom's maps mostly pull from the same set of textures and map features, instead in DF, each map represents a space filled with unique art assets and bespoke little set pieces and puzzles, tailored to the objectives given to you by the larger narrative.
Similarly Marathon (1994) and its sequels charted their own oddball path, presenting its narrative almost solely through text based terminals scattered over the levels. Marathon tells stories about the nature of player agency and free will, of creatures beyond human comprehension, how aliens explode real good when you shoot them enough; and it does it essentially by smashing together a visual novel and an fps.
All that to say, its pretty great. It shipped with a multiplayer mode that was pretty popular in these days, but which nowadays has been eclipsed by the single player campaigns.
As part of the third game's slightly bonkers meta narrative, Bungie also released the tools they used to craft levels. In the narrative this is part of the blurring between the player/player character and their ability to reshape the world infinitely to their liking, but more importantly, it led to a small but dedicated map making community. In combination with the Marathon games being open sourced decades ago, the scene has been ticking along quietly for the last 30 years as far as I can tell.
Which brings us to Marathon: Apotheosis X.
Apotheosis X began life as an unfinished total conversion from my teenage years. That unfinished build has been floating around the net since 2007. In 2020 I became interested in modding again and resolved to finish the project. As usual, ambition eclipsed good sense, and over the next 2 years my team and I remade nearly everything in the game from scratch.