For the most part this level is short and easy having only one dream scene, the 2nd one, which puts you to the test. Did I do the level no scratch, well...yes and no. You see I could have labored endlessly for hours trying desperately to make the outcome of 2 particular spots in the level result in no health loss. In fact I did on one rare instance manage to pull that off in the 2nd of the 2 spots, but it is still a mystery to me exactly how I did it.
Suffice it to say that no visible foe harmed me and the 2 health point drops were not for lack of reflexes or marksmanship. I decided I wasn't going to lose any sleep over what is basically an odd scripting of the game that may or may not allow after repeated attempts the rare and random no scratch outcome on BOTH those spots. THAT IMO would become an obsession with solving a scripting puzzle rather than using typical tactical skills to get the no scratch, and I've never had much patience for puzzles, especially ones that don't really make sense.
The 2 spots I'm speaking of are when you exit the 2nd dream scene and approaching the middle of the bridge leaving the vault. I even had a video clip of doing the latter no scratch but considered it rather insignificant unless the video showed the entire level no scratch. I also wanted to prove a point in showing the video WITH the 1 health point drops in each spot.
I have also included screenshots to back up my points. Here are two adjacent frames of the video where I encountered the last ghost before leaving the 2nd dream scene. http://img81.imageshack.us/img81/8320/vault1stdreamhealthry6.jpg http://img81.imageshack.us/img81/2055/vault1stdreamhealth2lp6.jpg This is to show that no ghosts in that dream scene caused the health drop.
Here is the frame showing where the 1 point health drop occurred (2 blood spots at top center), 12 frames after the last sighting of ghost in the 2nd dream scene and well into the escape of it. http://img295.imageshack.us/img295/4156/vault1stdreamhealth3ez5.jpg There is a mysterious invisible force that typically shatters the glass of the wall cabinet to your left as you leave the 2nd dream scene. In the video I shoot that cabinet's glass out BEFORE entering the dream scene. This leaves no audible or visible prescene of the mysterious force, yet the health drop still occurs.
Here are 2 adjacent frames of the 2nd 1 point health drop approaching the middle of the bridge leaving the vault. http://img295.imageshack.us/img295/7641/vaultbridgehealthgy1.jpg http://img295.imageshack.us/img295/159/vaultbridgehealth2xf0.jpg As you can see the health drop occurrs well before the ghosts or even a glimpse of their bubbles are visible and there isn't even any visible damage indicator on the screen (blood at the edge of the shot).
Another odd thing I decided to leave in was the 3rd reactor core shot fired, though I aimed at the left closest one, the one on the left behind it exploded, weird. I found out via test runs that though the last set of ghosts will not see or approach you if you're standing on the railing (unless you get too close, which is why I shoot one of them), the set of ghosts before them, the ones after destroying the reactor cores, still see and approach you if on the railing and far away. The only other oddity I can think of in this level is it's common if you get too close to the ghosts in the dream scenes they will take some armor points off, but not health, yet this mysterious force always drops you 1 health point, but no armor.
Of course that mysterious force could be and probably IS Alma, but they could at least show her present when it occurrs to make more sense out of it. I tried desperately to use the brief moment they show her when you're entering the room where the 2nd dream scene occurs to shoot her in the head with both the pistol and the cannon, but still the same outcome. I also tried jumping when leaving the dream scene as I seem to recall doing that on the railing when approaching the bridge no scratch, still no luck.
Level time roughly 7:20, mode Extreme, 2 mysterious health points lost, music is Reflection, by Tool.