Critical Mass is for version 1.4/1.5. It has 3 levels and the file is 2.0MB in size. The file name is dncm.zip. It was released on January 17, 2003.

Critical Mass has very good level design and gameplay with a good health/ammo to enemies ratio. There are 4 new weapons and 5 of the enemies have new or different attacks/weapons. There are also some new pickups like the ammo for the BFG-9000 from Doom. The facing of the walls of the lobby on the first level are breakable and there are new textures and tinted breakable windows. There are new bar style force fields, one moving the other stationary with some of them being almost harmless and the others lethal. The only minor fault I found is the dual pistols are placed a little too high up and can interfere with your view. I rate this TC as very good with 4 out of 5 stars.