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[Scatty]

Well the fog effect was used by the Rise of the Triad engine, and the talking to friendly NPC's was a feature of Blake Stone, which slightly predated Doom but ultimately lost to it's power when it came out.
Up-Down looking was available in Heretic, which I believe came out before Duke Nukem 3D. Weapons similar in functioning and graphic effects to flamethrower, and exploding grenades, were also present in Heretic.

I guess this Mars 3D game pulled bits and pieces from different game engines and jammed them together into this, so hack is probably a fitting word for it.