Chasm is a 1997 FPS made by the Ukrainian Action Forms Ltd, who would later make Vivisector and the better-known-but-still-obscure Cryostasis: The Sleep of Reason. It's heavily inspired by the original Quake, to the extent that you can easily call it a "Quake Clone" or even a cheap knockoff. In fact, it seems to have originally positioned itself as an alternative to Quake that would run on older, 486 PCs while looking 'just as good'. The dark secret that makes this possible is that while all enemies, weapons, and objects are polygonal 3D models, the terrain is rendered using raycasting in a manner not dissimilar to the Doom and Build engines. Thanks to its clever texture work, it could easily fool just about anybody. Chasm easily competes with id software's visuals more than, for instance, Blood, which also came out in '97.
For a long time the only way to play this game on modern OSes was through DOSbox. I played using a source port called PanzerChasm. With this source port I was able to run the game using OpenGL, at 1440p, and with modern, more configurable controls. Unfortunately, it's also at only version 0.3 at the time of writing and it sometimes shows. I did run into a number of what would have been progress-halting bugs if I hadn't had the option to pull down the console and cheat, usually by noclipping through a door that didn't open when it was meant to and such. That stuff is unfortunate, but all of the errors seem to be related to scripted events not triggering properly. I never dealt with any crashes or systemic errors.
Overall, Chasm feels pretty good to play. A problem that affects many of these obscure FPSses, especially ones made in places like Ukraine, is that they feel "janky." That is not the case here. Movement is tight and responsive, the weapons feel alright, and none of the enemies are inherently cheap (more on that later). Nothing about this game feels broken. Some levels try to spice things up with booby traps, and collision with them is iffy. I don't know if the game or the source port is to blame, however.
Level design is where Chasm falters the most. Quake made a point of showing off the benefits of a true-3D environment in its twisted, complex, and oftentimes vertically oriented level design. Blood had a raycasting engine, but leveraged the overhead afforded from sprites to provide large, clever environments. Chasm's attempt to do the best of both worlds works on a visual level, but severely hinders its level design. Without a true-3D engine it can't place rooms on top of one another or anything like that. By using textured polygonal models in place of sprites it doesn't have a lot of horsepower left over to do anything clever with its environments. The result is that Chasm's levels are flat, cramped, simplistic corridor crawls without a lot of variation. You walk down hallways, you push a switch that opens a door somewhere, you grab a key... it's very basic. The levels being small and cramped has another adverse effect. I said earlier that no enemy is inherently cheap, and that's true, but oftentimes the level design will simply not give you the space you need to maneuver. Weapons with splash damage are greatly disincentivized by the lack of breathing room. It turns what should be basic encounters into what instead feel like 'fuck you' traps that can kill you very quickly simply because you have no recourse to survive. So the enemies are, at times, made to be cheap by the level design.
So the enemies themselves aren't cheap, but they are kind of dull and have little variation in their behaviors. There are about eight different types of enemies that run at you and hit you with melee attacks. These enemies may look very different, and vary in terms of attack power and health points, but they're all more or less the same monster. Not a lot can happen that will inspire you to switch up your tactics, or even change which weapon you're carrying. The enemy behavior is so basic that the shotgun you get in the first level is the de-facto best choice for just about any situation. Spicing things up somewhat is a dismemberment system. With well placed shots you can blast the arms and/or head off of any enemy. Once a limb is gone, any enemy attack that required use of it is disabled. For instance, there is a lizardman enemy in episode 2 that holds a club in one hand and throws rocks with the other. Blast one arm off and he loses that respective attack. Blast both off and all he can do is pathetically headbutt you. There's a zombie enemy which will keep reviving unless decapitated. There's a revenant warrior enemy who will keep going even after being decapitated. It's cool and all, but doesn't amount to much in practice.
Chasm is very short. There are four episodes, and each episode only has four levels. Each episode ends in a boss fight, which are more like puzzles in which you indirectly kill the boss rather than engage in a shootout with them. I didn't like the boss fights very much.
I probably made this game sound a lot worse than it is. I had a pretty decent time with the game. Chasm displays a lot of basic competency for most of its running time, so the only noteworthy things to talk about are the moments when it dips slightly below that. If you like old school shooters, this is another one you probably haven't played before (or even heard of). It doesn't stand out for reasons good or bad. And that's fine. Chasm: The Rift is fine.
Chasm: The Rift is an obscurity that deserves better than to be forgotten, even if it is fairly dull.