'Doom: Fall of Mars - Conceptual Demo' is a pre-beta version of Doom FoM released a few weeks after it's announcement in august 2008.
This is the August 30th 2008 release. Here are some of the fixes if you have a previous version-
Update: August 30 2008: Technical Update Including HUD quick slots, Weapons, Enemies, Enemy info displays, Bosses, Items, and many bug fixes.
Update: August 27 2008: A quick update has been uploaded, fixes- Lag, Movement system, Screen shaking, In game menu.
***Please keep in mind that this is a VERY early release and is more of a concept than a game at this point.***