I can't get past the one where the open space is T-shaped, and the gap is too far to jump, and the ceiling is too low to stack the shadows and jump. (It's the one right after a similar one where there's a green forcefield over the gap and the door's in the air on the right.)
I'm getting the feeling you have to time jumps off of other jumpers' heads, but that's so hard to actually do.
Edit: Nevermind, just got it. That was more luck than planning, honestly.
Aw, that was the last level. Oh wellz. Great game, nice music, fun story. I always loved psycho-analytic stuff like that.