/vr/ - Retro Games

guys I need your help trying to remember the name of a really really old (and possibly obscure) FPS I played when I was a kid.

I don't remember much about it sadly other than the fact that it starred on this scifi laboratories type of environments (vaguest fucking description ever) alongside some offices and even bathrooms and holding cells full of ceiling sentrybots, mutants and robots and forcefields and all that shit. that's sadly all I could make of it. I do recall monitors and interactive computers scrapped around you could use to lower forcefields and open doors and shit. Yeah, I know, not the most detailed and less derivative description ever, yeah, but hear me out on this one thing because it's the only feature from this game that I can bring myself to remember as crystal fucking clear. What is it about it, you may ask?

It's pic related.

You see, as far as I remember, the game featured only ONE weapon throughout (didn't even finish it though), and it was this sort of black, overdetailed, voxel-y sci-fi machinegun with green and red (?) lights and a grip to the left my guy would hold always (not unlike, say, Doom 4's chaingun). There were 'weapon mods' for this gun oftentimes scattered around some of the levels of the game which altered this machinegun and sort of acted like doom's arsenal contained within one weapon. The clearest memory I have of this is that one of these mods had the player tilt the gun completely upwards and shoot a grenade or plasma bomb from the area around the grip, another one had the gun shoot a pellet-type shotgun round, and another one converted the weapon into a rocket launcher. None of these mods ever changed its look or appearance at all, just its fire abilities.

Please keep in mind that at least 20 or so years have passed since I last played it and my memory is fuzzy as FUCK, and this is all I can bring myself to remember. Hope you can help me out on this.