[PC] [late 90s-early 2000s] old sci fi fps. Only have memories.
When I was a kid in early 2000s I used to play this weird fps where you started on inside a station in another planet and enemies were frog-like aliens (probably just aliens but i called them frogs) they were humanoid, with armor and no helmet. I remember vividly the first area having a shortcut where you enter a vent and go to a different part of the station. There was a outside of the station but you mostly played inside.
It could be a DOS game or a doom clone. The graphics felt old for early 2000. I remember that you had a double pistol but remember nothing else.
I searched a lot for a game like this in multiple lists but never quite the one I remember. If anything here rings a bell, even if not 100% (memory is a tricky place) please post it here, thanks