What was the name of the early 90's computer game that starts with the letter D?

It was a first person action game where you would fly around the levels. The game featured gray-like levels, with inverted keyboard controls, weapons such as plasma, and once you found the boss, you had to find the exit of the level before it blew up. The title is something like Dement or Default or something, not sure.

What was the name of the early 90's computer game that starts with the letter D?
It is Descent. A great TRUE 3D game (polygonal, not sprite based like Doom). I still have a copy of it. If you want to play it, Descent and its sequels are on GOG.com. Get it from there, for it WILL work on Windows XP then, with little to no issues. It's $5.99 on there.
Reply:Descent
Reply:Decent ?
Reply:you are thinking of Doom or Descent
Reply:Doom?