Chasm: The Rift is a marginally above-average first-person shooter that would have probably been better known had it been released before the likes of Quake II and Jedi Knights.
Graphics reminds me of Quake but level design is something else.
I don`t mind 2.5D engine for levels because I am used to them in Doom, Heretic, Hexen and Duke Nukem 3D.
Gameplay is however interesting with all goodies that one shooter can have: explore the level, kill enemies, unlock the door, etc.
Enemies are interesting because of ability to cripple their limbs in order to kill them or to take off its weapon, but enemy will keep fighting with what has left.
Weapons are good, but game lacks more.
Boss fights are the most interesting part of the game because you don`t have just to shoot in order to kill him.
Because I like this game. ;)