I have only had two of them that I can remeber, both where when I was a kid too. They were both nightmares and are the only two nightmares I can ever remeber having.

The one I had when I was sick and I kept seeing it every time I closed my eyes. I even saw it once when I was awake, I guess I was more sick than I thought I was heh. I don't even remeber what that dream was about. I think it was kind of like a puzzle like Ev said. Except I remeber it moved and when I messed up it moved really fast. Some reason when it started moving really fast it scared me.