[PC] [early 2000’s] 3D sidescroller action shooter

Guys, I know this is going to be hard, bit I really want to find a game that I saw for a few seconds in a corner of my eye, around 20 years ago on my grirlfriend’s PC screen. It was a sidescroller similar to Duke Nukem Manhattan Project but it wasn’t it. It may as well be a mod to some game. Level I saw was kinda dark and sci-fi ish. You could move only in 2D space like in Contra, but graphics were 3D. It looked really interesting, so I hope we can dig it up.