I have played
Chasm through some time ago (not the add-on episode though, just the original game). I wouldn't say it's much
Duke-like per se, but calling it a
Quake clone would be also not entirely correct (although the developers obviously aimed at the
Quake-playing audience here

). The game is more slow-paced than
Quake, leaning towards the standards of the earlier instalments of the
Wolfenstein 3-D era. In the first episode, the designers tried to create some more realistically-looking locations, which does work (there are distinct areas like the computer room, conference room, refrigeration facility, troop barracks etc.); in the latter, time-travelling episodes, it's rather hard to talk about realism, but all the locations like the Egyptian temples and tombs, medieval castles etc. are all recognizable. What doesn't help a lot here is that the layout of the levels is often not very well thought out, and you have to do a lot of back-tracking with multiple "Where is it?" moments. It had never been too annoying for me though, and sometimes you have to solve interestingly designed puzzles to make your progress. What I really liked about
Chasm though are the
puzzle bosses, although I know some people dislike the game for exactly that reason. I guess the developers tried to please a wide audience of FPS players and at the same time introduce innovative features, which resulted in a little bit of this and a little bit of that. Perhaps they would have done it better if they focused more on the puzzle part, since there are no huge fight-outs with hordes of monsters in the entire game anyway. Another quite serious minus in the level design that could put off players is that the developers really spam scripted ambushes all too often.
But, on the bright side, there's a good deal of interactivity in the game, I remember playing the first level for the first time, blasting the street-lights in the base yard, then the glass in the window. That was pretty cool, although it doesn't serve any purpose gameplay-wise though. Overall,
Chasm deserves a steady B, and I think that it's drawback lie more in the general lack of polishing (nothing that an extensive testing wouldn't be able to fix), not in some serious design flaw that breaks the game.