How did you determine the difficulty level for each puzzle? Was there some objective measure you used or was it merely subjective?
It was pretty subjective. I had several people try out the puzzles, and got a rough idea of difficulty from that. It would be really interesting to have some objective data on it.
Oh yeah, I meant to ask - and I suppose this goes for anyone reading this: Were there any puzzles that you felt like the difficulty was way off?