Mayhem Demo Review

Looking good for an unfinished game. Perhaps you should call it that because it was very lacking in features. A demo should be 'of near completion' relative to the full game.
I did like the view distance in the third level. It made it look really dark and vulnerable. The gameplay was fun but the slow movement caused me to lose a lot of health. Sometimes when you round a corner it's hard to rotate your character to face the hidden monster. A mouse-guided crosshair would be the best choice but I can see what you were trying to achieve with the arrow keys.
Unfortunately there was no story. A good story is a major part of an FPS, don't forget to add one when you are done.
Good job. Try and add at least 10 more sound effects, 5 more graphic effects and after a bit more polishing it will be a different game!